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Sonodynamic therapy (SDT) is a prospective therapy for many tumors by activation of sonosensitizers to produce reactive oxygen species (ROS) by ultrasound (US). However, limited generation of ROS and low drug delivery efficiency of sonosensitizers to the tumor tissue still hinder the application of SDT. Herein, an amphiphilic rose bengal (ARB) conjugate was designed to fabricate rose bengal microbubbles (RB-MBs) with high drug-loading contents (∼6.8%) and excellent contrast enhancement capability for US imaging, well suited for detecting tumor location and size. More importantly, RB-MBs could be successfully converted into RB-NPs by local US exposure, resulting in ∼7.5 times higher drug accumulation at the tumor tissue through the sonoporation effect as compared to RB-NPs and RB-MBs without US sonication. Meanwhile, using RB as the MB shell facilitated US energy transfer by the US mediated collapse of MBs through either a sonoluminescence or pyrolysis process; thus, the ROS generation efficiency could be greatly enhanced, resulting in a significantly higher tumor inhibition rate for the RB-MBs + US (∼76.5%) in the HT-29 tumor model as compared to conventional MBs + US and RB-NPs + US (∼23.8% and ∼49.2%), respectively. All these results suggested that this novel sonosensitizer delivery system of RB-MBs combined with US is a powerful strategy for remarkably enhancing SDT therapeutic efficacy with minimal side effects, showing great potential in cancer theranostics.

Purpose: The novel molecular imaging probe 99mTc-HYNIC-H10F was developed for patient screening and efficacy monitoring of trastuzumab therapy by SPECT imaging of HER2 expression in breast cancer.

Methods: 99mTc-HYNIC-H10F was developed by labeling H10F peptide with 99mTc following an optimized protocol. Biodistribution and SPECT/CT were performed in mouse models bearing HER2-positive SK-BR3 and HER2-negative MDA-MB-231 human breast cancer xenografts, respectively. The treatment response to trastuzumab was monitored and quantified by SPECT/CT in two HER2-positive breast cancer models (SK-BR3 and MDA-MB-361). The preliminary clinical study was performed in two patients with breast cancer.

Results: SPECT/CT with 99mTc-HYNIC-H10F showed that the SK-BR3 tumors were clearly visualized, while the signals from MDA-MB-231 tumors were much lower. The tumor uptake of 99mTc-HYNIC-H10F could be blocked by excess unlabeled H10F peptide but not by excess trastuzumab. The growth of two HER2-positive tumors was prominently suppressed at day 11 post-treatment. However, SPECT/CT reflected much earlier therapy response at day 4 post-treatment. The HER2 expression in tumors of breast cancer patients could be detected by 99mTc-HYNIC-H10F SPECT/CT imaging.

Conclusions: 99mTc-HYNIC-H10F specifically accumulates in HER2-positive tumors. Compared with trastuzumab, 99mTc-HYNIC-H10F binds to a different domain of HER2 antigen, providing new opportunities to monitor HER2 expression levels before/during/after trastuzumab treatment for more effective personalized treatment.

Keywords: Breast cancer; HER2; SPECT/CT; Therapy monitoring; Trastuzumab.

Previously, we successfully developed the c(phg-isoDGRk) peptide as a novel integrin α5β1-targeted SPECT imaging probe 99mTc-HisoDGR for Glioma imaging. However, the fast clearance of 99mTc-HisoDGR in blood reduced its tumor accumulation and retention, which would be the obstacles for further clinical application. Dimerization and albumin-binding strategies have been proven as effective approaches to improve tumor targeting capability and blood circulation time of radiotracers. In this study, the novel PEGylated dimeric isoDGR peptides (termed 3PisoDGR2) and its analogue with an albumin binder (termed AB-3PisoDGR2) were designed, and the corresponding radiotracers 99mTc-3PisoDGR2 and 99mTc-AB-3PisoDGR2 were fabricated and assessed for tumor-targeting and in vivo pharmacokinetics properties in subcutaneous and orthotopic tumor models. The dimerization of isoDGR peptide provided higher binding affinity to tumor cells and longer blood circulation time than the original monomeric isoDGR peptide, resulting in twice increased tumor uptake (99mTc-3PisoDGR2 2.51 ± 0.17 %ID/g vs 99mTc-PisoDGR 1.17 ± 0.21 %ID/g, P < 0.01) at 0.5 h post-injection (p.i.) and enhanced tumor to nontargeting tissue ratios (T/NT) in most normal organs. The blocking study indicated that the tumor uptake was receptor-mediated specifically. NanoScanSPECT/CT imaging of 99mTc-3PisoDGR2 in glioma tumor-bearing model showed clear visions of tumors with low background, except high uptake in excretion system including kidneys and bladder at all detected time points (0.5, 1, and 2 h p.i.). The orthotopic glioma tumor could also be clearly visualized by nanoScanSPECT/CT imaging with 99mTc-3PisoDGR2. The addition of albumin-binding entity further prolonged blood circulation time and reached higher tumor uptake for 99mTc-AB-3PisoDGR2. However, since 99mTc-AB-3PisoDGR2 is less capable of passing BBB than 99mTc-3PisoDGR2, 99mTc-3PisoDGR2 is preferable for the in situ glioma imaging. In conclusion, 99mTc-3PisoDGR2 represents an improved molecular probe for integrin α5β1-targeted tumor imaging, showing more potential for further clinical application.

Colorectal cancer is a common malignant tumour with a low 5-year survival rate. A combination therapy with high selectivity and easy controllability is a pressing need for the effective treatment of such cancer. In this study, an indocyanine green derivative (Cy7)-conjugated lipid with a terminal carboxyl group was synthesized, which could self-assemble with a cerasome-forming lipid (CFL) into nanoparticles (NPs) by encapsulating doxorubicin (DOX) to achieve combined photothermal chemotherapy. The resulting Gly@Cy7-Si-DOX NPs with a surface covalent silicate framework showed excellent morphological stability and colloidal stability. Specifically, the conjugated Cy7 was covalently conjugated in the liposomal bilayer, resulting in high drug loading content, high photostability, and high photothermal conversion efficiency, which enabled the resulting nanoparticles to be an effective platform for photothermal therapy. Meanwhile, the encapsulated DOX leaked only slightly under physiological conditions due to the silicate surface of Gly@Cy7-Si-DOX NPs and exhibited controlled release in a weakly acidic environment or under near-infrared (NIR) light irradiation for chemotherapy. Gly@Cy7-Si-DOX NPs were efficiently taken up by tumour cells. Upon light irradiation, the released DOX entered the nuclei of tumour cells, as observed by confocal microscopy and flow cytometry. In vitro cell experiments indicated that both healthy cells and tumour cells were viable under treatment with only Gly@Cy7-Si-DOX NPs, indicating the encapsulated DOX was stably confined to the NPs, and cells were significantly killed when treated with both Gly@Cy7-Si-DOX NPs and NIR laser irradiation. After i.v. administration, Gly@Cy7-Si-DOX NPs accumulated at the tumour site, as monitored by near-infrared fluorescence imaging. A significant tumour inhibition rate (95.8%) was also achieved in a HT-29 colorectal cancer model when treated with Gly@Cy7-Si-DOX NPs plus irradiation. Therefore, the Gly@Cy7-Si-DOX NPs hold great promise for controllable combined colorectal cancer photothermal chemotherapy.

Doxorubicin (DOX) has been clinically used as a broad-spectrum chemotherapeutic agent for decades, but its clinical application is hindered by the lack of tumour specificity, severe cardiotoxicity and haematotoxicity. Pre-targeted strategies are highly tumour-specific, therapeutic approaches. Herein, a novel pre-targeted system was constructed, aiming to enhance anticancer efficacy of DOX and maximally reduce its side effects. Methods: The DOX prodrug (bDOX) was first synthesized by conjugating DOX with mini-PEGylated (mPEGylated) biotin through a pH-sensitive bond. During the pre-targeted treatment, avidin was first administrated. After an optimized interval, bDOX was second administrated. The nontoxic prodrug bDOX was eventually transformed into the toxic anticancer form (DOX) by a pH-triggered cleavage specifically in tumour cells. The drug efficacy and side effect of the two-step, pre-targeted treatment were fully compared with free DOX in vitro and in vivo. Results: The prodrug bDOX was quite stable under neutral conditions and nearly nontoxic, but was immediately transformed into the toxic anticancer form (DOX) under acidic conditions. Compared to free DOX, the pre-targeted bDOX exhibited a higher cellular uptake by human colorectal tumour cells (LS180 and HT-29 cells). In vivo evaluation performed on LS180 xenograft animal model demonstrated that the pre-targeted bDOX achieved a much more significant tumour inhibition than free DOX. The largely decreased, unwanted bystander toxicity was demonstrated by changes in body weight, cardiomyocyte apoptosis, blood routine examination and splenic pathological changes. Conclusion: The high therapeutic efficacy, together with the minimal side effects, of this easily synthesized, pre-targeted system exhibited immense potentiality for the clinical application of DOX delivery.

Keywords: avidin; biotin; chemotherapy; doxorubicin prodrug; pre-targeted strategy.

Antiangiogenic therapies have been demonstrated to improve the efficacy of immune checkpoint inhibition by overcoming the immunosuppressive status of the tumor microenvironment. However, most of the current antiangiogenic agents cannot discriminate tumor angiogenesis from physiological angiogenesis. The aim of this study was to investigate whether a photodynamic therapy (PDT) agent that targets CD276, a receptor overexpressed in various tumor cells and tumor vasculature but with limited expression in normal tissue vasculature, could improve the tumor inhibitory efficacy of a PD-1/PD-L1 blockade. A CD276-targeting agent (IRD-αCD276/Fab) was synthesized by conjugating the Fab fragment of an anti-CD276 antibody with a photosensitizer IRDye700. The in vivo tumor-targeting efficacy and therapeutic effects of IRD-αCD276/Fab with or without an anti-PD-1/PD-L1 blockade were tested in subcutaneous and lung metastatic tumor models. PDT using IRD-αCD276/Fab significantly suppressed the growth of subcutaneous 4T1 tumor and inhibited its lung metastasis. Moreover, it triggered in vivo antitumor immunity by increasing the activation and maturation of dendritic cells. Tumor PD-L1 levels were also markedly increased after PDT using IRD-αCD276/Fab, as evidenced by noninvasive PD-L1-targeted small-animal PET imaging. In combination with an anti-PD-1/PD-L1 blockade, IRD-αCD276/Fab PDT markedly suppressed the growth of tumors and prevented their metastasis to the lung by recruiting the tumor infiltration of CD8+ T cells. Our data provide evidence for the role of CD276-targeted PDT for local immune modulation, and its combination with PD-L1/PD-1 axis inhibition is a promising strategy for eliminating primary tumors as well as disseminated metastases, by generating local and systemic antitumor responses.

Keywords: PET imaging; angiogenesis; checkpoint inhibition; molecular imaging; photo-immunotherapy.

Increasing evidence indicates that the overexpression of galectin-1, a member of the galectin family, is related to tumor progression and invasion, as well as tumor resistance to therapies (e.g., radiotherapy). Herein, we investigated whether near-infrared fluorescence (NIRF) imaging and positron-emission tomography (PET) were sensitive approaches for detecting and quantitating galectin-1 upregulation in vivo. An anti-galectin-1 antibody was labeled with either an NIRF dye or 64Cu, and NIRF and PET imaging using the resulting probes (Dye-αGal-1 and 64Cu- 1,4,7-triazacyclononane-1,4,7-triacetic acid [NOTA]-αGal-1) were performed in 4T1 breast cancer-bearing mice treated with several rounds of sorafenib. Radiotherapy was performed in vitro and in vivo to identify the role of galectin-1 in radioresistance. NIRF and PET imaging both revealed significantly increased upregulation of galectin-1 in the hypoxic tumors after sorafenib treatment, which was verified by ex vivo biodistribution, western blotting, and enzyme-linked immunosorbent assays. Galectin-1 specific inhibition by thiodigalactoside dramatically improved the efficacy of radiotherapy, and overcame sorafenib-induced radiotherapy resistance. Taken together, galectin-1 is a key mediator of tumor resistance to radiotherapy. Targeted molecular imaging allows for real-time, noninvasive, and quantitative detection of the dynamic changes in galectin-1 levels in vivo; this introduces the possibility of early detection of tumor resistance to therapies.

Keywords: (64)Cu; Galectin-1; Hypoxia; ImmunoPET; Radiotherapy.

The metastatic spread of primary tumors to regional lymph nodes (LNs) is an important prognostic indicator for cancer staging and clinical therapy. Therefore, developing lymphatic mapping probes with improved accuracy and efficiency is of vital importance. Conjugated polymers (CPs) have been established as useful optical probes for sensitive biological and chemical detection. As a member of CPs family, polythiophene derivatives have drawn increasing attraction because of their superior photostability, signal amplification ability, and flexible structures for modification. In addition, these excellent properties allow the promising in vivo application to real-time LNs mapping. Here, we first reported a radiolabeled dual-modal probe based on the polythiophene derivative (99mTc-PTP) that was used for LNs mapping with high sensitivity and specificity by preoperative single-photon emission computed tomography imaging and intraoperative optical guidance. 99mTc-PTP exhibits an excellent radio-fluorescence guidance ability and a remarkable biocompatibility and holds great potential to be a powerful probe for noninvasive LNs mapping.

Keywords: SPECT imaging; dual modality; lymph nodes mapping; optical imaging; polythiophene.

Tumor relapse after initial regression post-chemotherapy is a major challenge in cancer treatment, as it usually leads to local-regional recurrence or inoperable distant metastasis. M2 macrophages diminish the tumor-inhibitory effect of chemotherapy and correlate with distant metastasis and poor prognosis. In this study, we investigated whether molecular imaging of M2 macrophages could serve as an early biomarker for tumor relapse after chemotherapy and tumor lymph node metastasis in preclinical mouse models. Methods: We developed M2 macrophage-targeted probes for near-infrared fluorescence (NIRF) imaging and single-photon emission computed tomography (SPECT) using an anti-CD206 monoclonal antibody. The specific targeting capacity and potential applications of the NIRF and SPECT probes were investigated in subcutaneous tumor and lymph node metastasis models of 4T1 murine breast cancer. Results: M2 macrophage infiltration was significantly increased in the 4T1 tumors that later underwent relapse but not in non-relapsing 4T1 tumors after cyclophosphamide treatment. Through NIRF imaging and SPECT using our synthesized probes, the infiltration of M2 macrophages in relapsing tumors and tumor lymph node metastasis could be sensitively detected. Importantly, early prediction of tumor relapse by molecular imaging of M2 macrophages resulted in an effective eradication of tumors upon combination with additional radiotherapy. Conclusion: Our findings demonstrate that M2 macrophage-targeted imaging allows for noninvasively predicting post-chemotherapy tumor relapse and sensitively detecting the metastatic lymph nodes in vivo. This imaging strategy could provide a better understanding of cancer progression, enable early prediction of tumor resistance, and have implications on the rational design of cancer therapeutics.

Keywords: CD206; M2 macrophage; Molecular imaging; SPECT; Tumor resistance.

Purpose: The role that gut microbiota plays in determining the efficacy of the anti-tumor effect of immune checkpoint inhibitors is gaining increasing attention, and fecal bacterial transplantation has been recognized as a promising strategy for improving or rescuing the effect of immune checkpoint inhibition. However, techniques for the precise monitoring of in vivo bacterial behaviors after transplantation are limited. In this study, we aimed to use metabolic labeling and subsequent positron emission tomography (PET) imaging to track the in vivo behaviors of gut bacteria that are responsible for the efficacy of anti-PD-1 therapy in living mice.

Methods: The antitumor effect of anti-PD-1 blockade was tested in a low-response 4T1 syngeneic mouse model with or without fecal transplantation and with or without broad-spectrum antibiotic imipenem treatment. High-throughput sequencing analyses of 16S rRNA gene amplicons in feces of 4T1 tumor-bearing mice pre- and post-anti-PD-1 treatment were performed. The identified bacteria, Bacteroides fragilis (B. fragilis), were labeled with 64Cu and fluorescence dye by the metabolic labeling of N3 followed by click chemistry. In vivo PET and optical imaging of B. fragilis were performed in mice after oral gavage.

Results: The disturbance of gut microbiota reduced the efficacy of anti-PD-1 treatment, and the combination of B. fragilis gavage and PD-1 blockade was beneficial in rescuing the antitumor effect of anti-PD-1 therapy. Metabolic oligosaccharide engineering and biorthogonal click chemistry resulted in successful B. fragilis labeling with 64Cu and fluorescence dye with high in vitro and in vivo stability and no effect on viability. PET imaging successfully detected the in vivo behaviors of B. fragilis after transplantation.

Conclusion: PET tracking by metabolic labeling is a powerful, noninvasive tool for the real-time tracking and quantitative imaging of gut microbiota. This strategy is clinically translatable and may also be extended to the PET tracking of other functional cells to guide cell-based adoptive therapies.

Keywords: 64Cu; Gut microbiota; Metabolic labeling; Molecular imaging; PET tracking.

.^99mTc-3PRGD₂ was prepared and longitudinal SPECT/CT was performed to monitor the progression (n = 8) and recovery (n = 5) of liver fibrosis induced in a rat model by means of thioacetamide (TAA) administration. The mean liver-to-background radioactivity per unit volume ratio was analyzed for comparisons between the TAA and control (saline) groups at different stages of liver fibrosis. Data were compared by using Student t and Mann-Whitney tests. Accumulation of ^99mTc-3PRGD₂ in the liver increased in proportion to the progression of fibrosis and TAA exposure time; accumulation levels were significantly different between the TAA and control groups as early as week 4 of TAA administration. Results of ex vivo immunofluorescence staining demonstrated the positive expression of integrin α_vβ₃ on the activated hepatic stellate cells, and the integrin αvβ3 levels in the liver corresponded to the results of SPECT/CT (R²= 0.75, P < .0001). ^99mTc-3PRGD2 SPECT/CT was successfully used to monitor the progression and recovery of liver fibrosis and shows potential applications for noninvasive diagnosis of early stage liver fibrosis.

                                         

Figure 3a: Blocking studies of ^99mTc-3PRGD2 in rats treated with saline or TAA. (a) SPECT/CT images of rats treated with saline (control) or TAA 30 minutes after intravenous injection of ^99mTc-3PRGD2 (74 MBq) with or without presence of blocking dose of c(RGDfK) (cRGD) or c(RADfK) (cRAD). Images were adjusted by using the same scale for all animals. (b) Bar chart shows mean liver-to-background radioactivity per unit volume ratio. *** =P < .0001.

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Radiology, 2016 May;279(2):502-12.

DOI:10.1148/radiol.2015150090

Publication Date(Web):Dec 14 ,2015

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    Noninvasive, real-time, quantitative measurement of key biomarkers associated with cancer therapeutic interventions could provide a better understanding of cancer biology. We investigated in this study whether incorporating multiple molecular imaging approaches could be used to guide dasatinib anti-Src therapy and aid in the rational design of a combination therapy regimen. Bioluminescence imaging, (18)F-FDG PET, integrin αvβ3-targeted SPECT/CT, and vascular endothelial growth factor-targeted near-infrared fluorescence imaging were performed before and after dasatinib treatment in a tumor mouse model. There was no significant difference in the bioluminescence imaging signal or (18)F-FDG tumor uptake in dasatinib-treated tumors compared with the control tumors. However, the uptake of (99m)T-3PRGD2 (integrin αvβ3-specific) and DyLight755-ranibizumab (vascular endothelial growth factor-specific) in the dasatinib-treated tumors was significantly lower than that in the control tumors. In vitro studies confirmed the antiangiogenic effects of dasatinib but indicated a lack of cytotoxicity. Dasatinib plus cytotoxic docetaxel elicited marked synergistic tumor growth inhibition in vivo. Visualization of post-Src inhibition tumor signatures through multiple imaging approaches facilitates sensitive and quantitative measurement of cancer biomarkers in vivo, thus aiding in the rational design of dasatinib combination therapy.

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Significant evidence has indicated that tumor-associated macrophages (TAMs) play a critical role in the proliferation, invasion, angiogenesis, and metastasis of a variety of human carcinomas. In this study, we investigated whether near-infrared fluorescence (NIRF) imaging using a macrophage mannose receptor (MMR; CD206)-targeting agent could be used to noninvasively visualize and quantify changes in TAMs in vivo. The CD206-targeting NIRF agent, Dye-anti-CD206, was prepared and characterized in vitro and in vivo. By using NIRF imaging, we were able to noninvasively image tumor-infiltrating macrophages in the 4T1 mouse breast cancer model. Importantly, longitudinal NIRF imaging revealed the depletion of macrophages in response to zoledronic acid (ZA) treatment. However, ZA alone did not lead to the inhibition of 4T1 tumor growth. We therefore combined anti-macrophage ZA therapy and tumor cytotoxic docetaxel (DTX) therapy in the mouse model. The results demonstrated that this combination strategy could significantly inhibit tumor growth as well as tumor metastasis to the lungs. Based on these findings, we concluded that CD206-targeted molecular imaging can sensitively detect the dynamic changes in tumor-infiltrating macrophages, and that the combination of macrophage depletion and cytotoxic therapy is a promising strategy for the effective treatment of solid tumors.

http://www.thno.org/v05p0597.htm

Peptides are excellent biointerface molecules and diagnostic probes with many advantages such as good penetration, short turnover time, and low cost. We report here an efficient peptide screening strategy based on in situ single bead sequencing on a microarray. Two novel peptides YLFFVFER (H6) and KLRLEWNR (H10) specifically binding to the tumor biomarker human epidermal growth factor receptor 2 (HER2) with aKD of 10(-8) M were obtained from a 10(5) library. Conjugated to nanoparticles, both the H6 and H10 probes showed specific accumulation in HER2-positive tumor tissues in xenografted mice by in vivo imaging.

http://dx.doi.org/10.1021/acs.analchem.5b01588

Well-defined water-soluble block copolymers poly(ethylene glycol)-b-poly(N-(2-hydroxypropyl) methacrylamide-co-N-methacryloylglycylglycine) (PEG-b-P(HPMA-co-MAGG)) and their doxorubicin (Dox) conjugates with different composition and molecular weight were synthesized. These Dox conjugates can form micelles in buffer solution. The physicochemical properties, in vivo biodistribution, blood clearance, and especially the tumor accumulation of copolymers and micelles were studied. Severe liver accumulation can be observed for PEG-b-PMAGG copolymers. This was quite different from their Dox conjugate for which decreased RES uptake and elevated kidney accumulation could be observed. When decrease the negative charge to an appropriate amount such as 8-10 mol %, both RES uptake and kidney accumulation could be suppressed. Obvious tumor accumulation could be achieved especially when the molecular weight were increased from ∼40 to ∼80 KDa. These results provided us with a guideline for the design of nanoscaled drug delivery system as well as a potential option for treating kidney-related cancers.

http://dx.doi.org/10.1021/acs.biomac.5b00460

Cancer-targeted radionuclide therapy is a promising approach for the treatment of a wide variety of malignancies, especially those resistant to conventional therapies. However, to improve the use of targeted radionuclide therapy for the management of cancer patients, the in vivo behaviors, dosimetry, and efficacy of radiotherapeutic agents need to be well characterized and monitored. Molecular imaging, which is a powerful tool for the noninvasive characterization and quantification of biological processes in living subjects at the cellular and molecular levels, plays an important role in the guidance of cancer radionuclide therapy. In this review, we introduce the radiotherapeutics for cancer-targeted therapy and summarize the most recent evidence supporting the use of molecular imaging to guide cancer radionuclide therapy.

http://www.eurekaselect.com/131812/article

Integrin αvβ6 is widely upregulated in variant malignant cancers but is undetectable in normal organs, making it a promising target for cancer diagnostic imaging and therapy. Using streptavidin-biotin chemistry, we synthesized an integrin αvβ6-targeted near-infrared phthalocyanine dye-labeled agent, termed Dye-SA-B-HK, and investigated whether it could be used for cancer imaging, optical imaging-guided surgery, and phototherapy in pancreatic cancer mouse models. Dye-SA-B-HK specifically bound to integrin αvβ6 in vitro and in vivo with high receptor binding affinity. Using small-animal optical imaging, we detected subcutaneous and orthotopic BxPC-3 human pancreatic cancer xenografts in vivo. Upon optical image-guidance, the orthotopically growing pancreatic cancer lesions could be successfully removed by surgery. Using light irradiation, Dye-SA-B-HK manifested remarkable antitumor effects both in vitro and in vivo. (18)F-FDG positron emission tomography (PET) imaging and ex vivo fluorescence staining validated the observed decrease in proliferation of treated tumors by Dye-DA-B-HK phototherapy. Tissue microarray results revealed overexpression of integrin αvβ6 in over 95% cases of human pancreatic cancer, indicating that theranostic application of Dye-DA-B-HK has clear translational potential. Overall, the results of this study demonstrated that integrin αvβ6-specific Dye-SA-B-HK is a promising theranostic agent for the management of pancreatic cancer.

http://linkinghub.elsevier.com/retrieve/pii/S0142-9612(15)00231-8

β-Emitters can produce Cerenkov radiation that is detectable by Cerenkov luminescence imaging (CLI), allowing the combination of PET and CLI with one radiotracer for both tumor diagnosis and visual guidance during surgery. Recently, the clinical feasibility of CLI with the established therapeutic reagent Na(131)I and the PET tracer (18)F-FDG was demonstrated. (68)Ga possesses a higher Cerenkov light output than (18)F and (131)I, which would result in higher sensitivity for CLI and improve the outcome of CLI in clinical applications. However, the research on (68)Ga-based tumor-specific tracers for CLI is limited. In this study, we examined the use of (68)Ga-radiolabeled DOTA-3PRGD2 ((68)Ga-3PRGD2) for dual PET and CLI of orthotopic U87MG human glioblastoma. For this purpose, the Cerenkov efficiencies of (68)Ga and (18)F were measured with the IVIS Spectrum system (PerkinElmer, USA). The CLI signal intensity of (68)Ga was 15 times stronger than that of (18)F. PET and CLI of (68)Ga-3PRGD2 were performed in U87MG human glioblastoma xenografts. Both PET and CLI revealed a remarkable accumulation of (68)Ga-3PRGD2 in the U87MG human glioblastoma xenografts at 1 h p.i. with an extremely low background in the brain when compared with (18)F-FDG. Furthermore, (68)Ga-3PRGD2 was used for dual PET and CLI of orthotopic human glioblastoma. The orthotopic human glioblastoma was clearly visualized by both imaging modalities. In addition, the biodistribution of (68)Ga-3PRGD2 was assessed in normal mice to estimate the radiation dosimetry. The whole-body effective dose is 20.1 ± 3.3 μSv/MBq, which is equal to 3.7 mSv per whole-body PET scan with a 5 mCi injection dose. Thus, (68)Ga-3PRGD2 involves less radiation exposure in patients when compared with (18)F-FDG (7.0 mSv). The use of (68)Ga-3PRGD2 in dual PET and CLI shows great promise for tumor diagnosis and image-guided surgery.

http://dx.doi.org/10.1021/acs.bioconjchem.5b00169

PURPOSE:

This study aimed to explore the diagnostic performance of single photon emission computed tomography / computerized tomography (SPECT/CT) using a new radiotracer 99mTc-RGD-BBN for breast malignant tumor compared with 99mTc-3P4-RGD2.

METHODS:

6 female patients with breast malignant tumors diagnosed by fine needle aspiration cytology biopsy (FNAB) who were scheduled to undergo surgery were included in the study. 99mTc-3P4-RGD2 and 99mTc-RGD-BBN were performed with single photon emission computed tomography (SPECT) at 1 hour after intravenous injection of 299 ± 30 MBq and 293 ± 32 MBq of radiotracers respectively at separate day. The results were evaluated by the Tumor to non-Tumor ratios (T/NT). 99mTc-RGD-BBN and 99mTc-3P4-RGD2 SPECT/CT images were interpreted independently by 3 experienced nuclear medicine physicians using a 3-point scale system. All of the samples were analyzed immunohistochemically to evaluate the integrin αvβ3 and gastrin-releasing peptide receptor (GRPR) expression. The safety, biodistribution and radiation dosimetry of 99mTc-RGD-BBN were also evaluated in the healthy volunteers.

RESULTS:

No serious adverse events were reported in any of the patients during the study. The effective radiation dose entirely conformed to the relevant standards. A total of 6 palpable malignant lesions were detected using 99mTc-RGD-BBN SPECT/CT with clear uptake. All malignant lesions were also detected using 99mTc-3P4-RGD2 SPECT/CT. The results showed that five malignant lesions were with clear uptake and the other one with barely an uptake. 4 malignant cases were found with both αvβ3 and GRPR expression, 1 case with only GRPR positive expression (integrin αvβ3 negative) and 1 case with only integrin αvβ3 positive expression (GRPR negative).

CONCLUSION:

99mTc-RGD-BBN is a safe agent for detecting breast cancer. 99mTc-RGD-BBN may have the potential to make up for the deficiency of 99mTc-3P4-RGD2 in the detection of breast cancer with only GRPR positive expression (integrin αvβ3 negative). The preliminary application of 99mTc-RGD-BBN has demonstrated its powerful potential in breast cancer diagnosis and therapy.

http://www.ncbi.nlm.nih.gov/pmc/articles/pmid/25849333/

A series of radiolabeled peptides have been designed and optimized for tumor-targeted peptide receptor radionuclide therapy (PRRT). Pre-clinical and clinical applications of PRRT have shown promising results on tumor response, overall survival, and quality of life in patients with several kinds of tumors. (90)Y-DOTA-TOC and (177)Lu-DOTA-TATE are two of the most common radiopharmaceuticals with symptomatic improvements and complete clinical data. In addition to somatostatin analogs, radiolabeled peptides have been developed to target the relative receptors overexpressed in the tumors, such as integrin αvβ3, gastrin-releasing peptide receptor (GRPR), melanocortin-1 receptor (MC1-R), cholecystokinin (CCK) receptor, and glucagon-like peptide-1 receptor (GLP-1R). Several strategies have been designed to improve the therapeutic efficacy of PRRT. For instance, radiolabeled peptides could be optimized by the amino acid modification and radionuclide selection. Healthy tissue protective agents and multi-cycle procedures could effectively decrease the side effects of PRRT. Furthermore, combination treatments, including PRRT combined with surgery, chemotherapeutic agents, or radiosensitizing agents could be applied to increase the effectiveness of PRRT. In this review, the current progress of peptide-based radiopharmaceuticals for tumor-targeted PRRT was summarized. Radiopharmaceuticals currently under clinical investigation were also described.http://www.eurekaselect.com/114557/article

Cetuximab is an antiepidermal growth factor receptor (EGFR) monoclonal antibody that has received the approval of the Food and Drug Administration (FDA) for cancer treatment. However, most clinical studies indicate that cetuximab can only elicit positive effects on a subset of cancer patients. Inthis study, we investigated whether near-infrared fluorescence (NIRF) imaging of tumor vascular endothelial growth factor (VEGF) expression could be a biomarker for tumor early response to cetuximab therapy in preclinical wild-type and mutant tumor models of the KRAS gene. The treatment efficacy of cetuximab was determined in both HT-29 (wild-type KRAS) and HTC-116 (mutant KRAS) human colon cancer models. A VEGF-specific optical imaging probe (Dye755-Ran) was synthesized by conjugating ranibizumab (an anti-VEGF antibody Fab fragment) with a NIRF dye. Serialoptical scans with Dye755-Ran were performed in HT-29 and HTC-116 xenograft models. By using longitudinal NIRF imaging, we were able to detectearly tumor response on day 3 and day 5 after initiation of cetuximab treatment in the cetuximab-responsive HT-29 tumor model. Enzyme-linked immunosorbent assay (ELISA) confirmed that cetuximab treatment inhibited human VEGF expression in the KRAS wild-type HT-29 tumor but not inthe KRAS mutant HCT-116 tumor. We have demonstrated that the antitumor effect of cetuximab can be noninvasively monitored by serialfluorescence imaging using Dye755-Ran. VEGF expression detected by optical imaging could serve as a sensitive biomarker for tumor early responseto drugs that directly or indirectly act on VEGF.

http://dx.doi.org/10.1021/mp5002944

Antiangiogenic therapy is an effective strategy to inhibit tumor growth. Endostar, as an approved antiangiogenesis agent, inhibits the newborn vascular endothelial cells, causing the decrease of integrin αvβ3 expression. Radiolabeled 3PRGD2, a novel PEGlayted RGD dimer probe (PEG4-E[PEG4-c(RGDfK)]2) showed highly specific targeting capability to integrin αvβ3, which could be used for monitoring the efficacy of Endostar antiangiogenic therapy. In this study, (68)Ga-3PRGD2 PET imaging was performed in Endostar treated/untreated Lewis Lung Carcinoma (LLC) mice on days 3, 7, 14, and 21 post-treatment for monitoring the tumor response to Endostar treatment, with the (18)F-FDG imaging as control. As a result, (68)Ga-3PRGD2 PET reflected the tumor response to Endostar antiangiogenic therapy much earlier (day 3 post-treatment vs day 14 post-treatment) and more accurately than that of (18)F-FDG metabolic imaging, which provides new opportunities to develop individualized therapeutic approaches, establish optimized dosages and dose intervals for effective treatment that improve the survival rate of patients.

http://dx.doi.org/10.1021/mp5003202

Integrin αvβ3 is overexpressed in both neovasculature and glioma cells. We aimed to evaluate (68)gallium-BNOTA-PRGD2 ((68)Ga-PRGD2) as a new reagent for noninvasive integrin αvβ3 imaging in glioma patients. With informed consent, 12 patients with suspicious brain glioma, as diagnosed by enhanced magnetic resonance imaging (MRI) scanning, were enrolled to undergo (68)Ga-PRGD2 PET/CT and (18)F-FDG PET/CT scans before surgery. The preoperative images were compared and correlated with the pathologically determined WHO grade. Next, the expression of integrin αvβ3, CD34, and Ki-67 were determined by immunohistochemical staining of the resected brain tumor tissue. Our findings demonstrated that (68)Ga-PRGD2 specifically accumulated in the brain tumors that were rich of integrin αvβ3 and other neovasculature markers, but not in the brain parenchyma other than the choroid plexus. Therefore, (68)Ga-PRGD2 PET/CT was able to evaluate the glioma demarcation more specifically than (18)F-FDG PET/CT. The maximum standardized uptake values (SUVmax) of (68)Ga-PRGD2, rather than those of (18)F-FDG, were significantly correlated with the glioma grading. The maximum tumor-to-brain ratios (TBRmax) of both tracers were significantly correlated with glioma grading, whereas (68)Ga-PRGD2 seemed to be more superior to (18)F-FDG in differentiating high-grade glioma (HGG) from low-grade glioma (LGG). Moreover, (68)Ga-PRGD2 PET/CT showed different accumulation patterns for HGG of WHO grades III and IV. This is the first noninvasive integrin imaging study, to the best of our knowledge, conducted in preoperative patients with different grades of glioma, and it preliminarily indicated the effectiveness of this novel method for evaluating glioma grading and demarcation.

http://dx.doi.org/10.1021/mp5003224

We report the design, synthesis, and evaluation of a series of novel cyclopentadienyl tricarbonyl (99m)Tc complexes as potent σ1 receptor radioligands. Rhenium compounds 3-(4-(1,3-benzodioxol-5-ylmethyl)piperazin-1-yl)propylcarbonylcyclopentadienyl tricarbonyl rhenium (10a) and 4-(4-(1,3-benzodioxol-5-ylmethyl)piperazin-1-yl)butylcarbonylcyclopentadienyl tricarbonyl rhenium (10b) possessed high in vitro affinity for σ1 receptors and moderate to high selectivity for σ2 receptors and the vesicular acetylcholine transporter. Biodistribution studies in mice demonstrated high initial brain uptake for corresponding (99m)Tc derivatives [(99m)Tc]23 and [(99m)Tc]24 of 2.94 and 2.13% injected dose (ID)/g, respectively, at 2 min postinjection. Pretreatment of haloperidol significantly reduced the radiotracer accumulation of [(99m)Tc]23 or [(99m)Tc]24 in the brain. Studies of the cellular uptake of [(99m)Tc]23 in C6 and DU145 tumor cells demonstrated a reduction of accumulation by incubation with haloperidol, 1-(3,4-dimethoxyphenethyl)-4-(3-phenylpropyl)piperazine (SA4503), or 1,3-di-o-tolyl-guanidine (DTG). Furthermore, blocking studies in C6 glioma-bearing mice confirmed the specific binding of [(99m)Tc]23 to σ1 receptors in the tumor.

http://dx.doi.org/10.1021/jm5009488

PURPOSE:

Targeted radiotherapy (TRT) is an emerging approach for tumor treatment. Previously, 3PRGD2 (a dimeric RGD peptide with 3 PEG4 linkers) has been demonstrated to be of advantage for integrin αvβ3 targeting. Given the promising results of (99m)Tc-3PRGD2 for lung cancer detection in human beings, we are encouraged to investigate the radiotherapeutic efficacy of radiolabeled 3PRGD2. The goal of this study was to investigate and optimize the integrin αvβ3 mediated therapeutic effect of (177)Lu-3PRGD2 in the animal model.

EXPERIMENTAL DESIGN:

Biodistribution, gamma imaging and maximum tolerated dose (MTD) studies of (177)Lu-3PRGD2 were performed. The targeted radiotherapy (TRT) with single dose and repeated doses as well as the combined therapy of TRT and the anti-angiogenic therapy (AAT) with Endostar were conducted in U87MG tumor model. The hematoxylin and eosin (H&E) staining and immunochemistry (IHC) were performed post-treatment to evaluate the therapeutic effect.

RESULTS:

The U87MG tumor uptake of (177)Lu-3PRGD2 was relatively high (6.03 ± 0.65 %ID/g, 4.62 ± 1.44 %ID/g, 3.55 ± 1.08 %ID/g, and 1.22 ± 0.18 %ID/g at 1 h, 4 h, 24 h, and 72 h postinjection, respectively), and the gamma imaging could visualize the tumors clearly. The MTD of (177)Lu-3PRGD2 in nude mice (>111 MBq) was twice to that of (90)Y-3PRGD2 (55.5 MBq). U87MG tumor growth was significantly delayed by (177)Lu-3PRGD2 TRT. Significantly increased anti-tumor effects were observed in the two doses or combined treatment groups.

CONCLUSION:

The two-dose TRT and combined therapy with Endostar potently enhanced the tumor growth inhibition, but the former does not need to inject daily for weeks, avoiding a lot of unnecessary inconvenience and suffering for patients, which could potentially be rapidly translated into clinical practice in the future.

http://www.ncbi.nlm.nih.gov/pmc/articles/pmid/24505234/

Integrins, a family of cell adhesion molecules composed of α and β heterodimeric subunits, are involved in a wide range of cell-extracellular matrix and cell-cell interactions. The study of integrin family members as targets for molecular imaging and therapy has been generally limited with the exception of integrin αvβ3. vβ6, a member of the integrin family, is expressed at low or undetectable levels in normal tissues, but is widely upregulated during many pathological and physiological processes, especially cancer and fibrosis, making it a promising target for molecular imaging. Noninvasive and quantitative imaging of integrin vβ6 expression would be very useful for disease diagnosis, treatment monitoring, and prognosis assessment. Although various molecular probes have been developed for positron emission tomography and single-photon emission computed tomography imaging of integrin vβ6 expression in preclinical animal models, further research efforts are required to optimize integrin vβ6-targeting probes for future potential clinical applications in the fields of oncology and beyond.

http://www.ncbi.nlm.nih.gov/pmc/articles/pmid/24982819/

The present study reports a new approach for synthesizing (111)In-radiolabeled biocompatible Fe3O4 nanoparticles. Radioactive (111)In is doped in situ into the lattice of Fe3O4 nanoparticles to achieve robust radiolabeling for accurately tracing PEGylated Fe3O4 particles in vivo.

http://dx.doi.org/10.1039/c3cc48948e

The aim of this study was to explore the diagnostic performance of 99mTc-3(poly-(ethylene glycol),PEG)4-RGD2 (99mTc-3PRGD2) scintimammography (SMM) in patients with either palpable or nonpalpable breast lesions and compare SMM to mammography to assess the possible incremental value of SMM in breast cancer detection. We also investigated the αvβ3 expression in malignant and benign breast lesions. Ninety-four patients with 110 lesions were included in this study. Mammograms were evaluated according to the Breast Imaging Reporting and Data System (BI-RADS) by a specialized imaging radiologist. Prone SMM was performed 1 hour after injection of 99mTc-3PRGD2. Scintigraphic images were interpreted independently by two experienced nuclear medicine physicians using a three-point system, and the kappa value was calculated to determine the interreader agreement. The McNemar test was used to compare SMM and mammography with respect to sensitivity, specificity, and accuracy. Diagnostic values for breast cancer detection were evaluated for each lesion. Immunohistochemistry was performed to evaluate integrin αvβ3 expression. Histopathology revealed 46 malignant lesions and 64 benign lesions. The overall sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of SMM were 83%, 73%, 77%, 69%, and 85%, respectively. The kappa value between the two reviewers was 0.63. The diagnostic values of SMM were higher than those of mammography in evaluating overall breast lesions. A sensitivity of 91% was achieved when SMM and mammography results were combined with 60% of all false-negative mammography findings classified as true-positive results by SMM. Integrin αvβ3 expression was positively identified using SMM imaging. SMM is a promising tool to avoid unnecessary biopsies when used in addition to mammography and can be used to image αvβ3 expression in breast cancer with good image quality.

http://dx.doi.org/10.2310/7290.2014.00010

The protein, thyroid hormone-responsive SPOT 14 homolog (Thrsp), has been reported to be a lipogenic gene in cultured hepatocytes, implicating an important role of Thrsp in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Thrsp expression is known to be regulated by a variety of transcription factors, including thyroid hormone receptor, pregnane X receptor, and constitutive androstane receptor. Emerging in vitro evidence also points to a critical role of liver X receptor (LXR) in regulating Thrsp transcription in hepatocytes. In the present study, we showed that Thrsp was up-regulated in livers of db/db mice and high-fat-diet-fed mice, two models of murine NAFLD. Hepatic overexpression of Thrsp increased triglyceride accumulation with enhanced lipogenesis in livers of C57Bl/6 mice, whereas hepatic Thrsp gene silencing attenuated the fatty liver phenotype in db/db mice. LXR activator TO901317 induced Thrsp expression in livers of wild-type (WT) and LXR-β gene-deficient mice, but not in LXR-α or LXR-α/β double-knockout mice. TO901317 treatment significantly enhanced hepatic sterol regulatory element-binding protein 1c (SREBP-1c) expression and activity in WT mice, but failed to induce Thrsp expression in SREBP-1c gene-deficient mice. Sequence analysis revealed four LXR response-element-like elements and one sterol regulatory element (SRE)-binding site within a -2,468 ∼+1-base-pair region of the Thrsp promoter. TO901317 treatment and LXR-α overexpression failed to induce, whereas overexpression of SREBP-1c significantly increased Thrsp promoter activity. Moreover, deletion of the SRE site completely abolished SREBP-1c-induced Thrsp transcription.

CONCLUSION:

Thrsp is a lipogenic gene in the liver that is induced by the LXR agonist through an LXR-α-mediated, SREBP-1c-dependent mechanism. Therefore, Thrsp may represent a potential therapeutic target for the treatment of NAFLD.

http://dx.doi.org/10.1002/hep.26272

Integrin αvβ3 has been recognized to play an important role in angiogenesis, tumor growth and metastasis. It will be of interest to apply this promising target for tumor imaging and visualization of tumor angiogenesis in vivo. In this study, a novel integrin αvβ3 targetting imaging probe, (99m)Tc-HYNIC-E[c(RGDfK)]2, was used to investigate the glioma uptake in vitro and in vivo before and after treatment with an antiangiogenic agent, endostar. The results indicated that U87MG glioma cells have high expression of integrin αvβ3 and special uptake of (99m)Tc-HYNIC-E[c(RGDfK)]2 both in cell line and in tumor xenograft. The endostatin analogue endostar can inhibit the expression of integrin αvβ3 receptors in both U87MG cells in vitro and gliomatissues, which suggested that integrin pathway may play a role in antiangiogenic effect of Endostar. (99m)Tc-HYNIC-E[c(RGDfK)]2 may be a promising molecular imaging probe for integrin αvβ3 positive tumor imaging and open up the possibility to establish an molecular imaging modality for assessment of tomor antiangiogenic therapy.

http://linkinghub.elsevier.com/retrieve/pii/S0304-3835(13)00111-0

There is a critical need to develop diagnostic procedures enabling early detection of tumors while at a curable stage. Technetium 99m (99mTc)-labeled VQ peptide (99mTc-HYNIC-VQ) identified through screening phage display peptide libraries against fresh human colonic adenomas was prepared and evaluated for tumor detection. 99mTc-HYNIC-VQ was prepared by a non-SnCl2 method with more than 99% radiochemical purity. The biodistribution in the HT-29 tumor model showed that although the absolute tumor uptake values were relatively low (0.60 ± 0.09, 0.41 ± 0.09, 0.36 ± 0.18, and 0.19 ± 0.08 %ID/g at 0.5, 1, 2, and 4 hours postinjection, respectively), the tumor uptake was higher than that of any of the other organs except for the kidneys at any time point examined, which led to the high tumor to nontarget ratios. The tumors and inflammation were clearly visualized with high contrast. Although the mechanism of accumulation of radiolabeled VQ peptide in tumors and inflammation needs to be further investigated, 99mTc-HYNIC-VQ is a promising imaging agent for the early detection of tumors or premalignancies, at least for screening patients with a high risk of developing cancers.

Differently sized NaGdF(4) nanocrystals with narrow particle size distributions were synthesized by a high temperature approach. Upon ligand exchange, the as-prepared hydrophobic NaGdF(4) nanocrystals were transferred into water by using asymmetric PEGs simultaneously bearing phosphate and maleimide groups. Further investigations demonstrated that the water-soluble NaGdF(4) nanocrystals, coated by PEG bearing two phosphate groups on the same side, exhibit not only excellent colloidal stability in water and PBS buffer, but also higher T1 relaxivity than Gd-DTPA (Magnevist). Through "click" reaction between the maleimide residue on particle surface and thiol group from the partly reduced anti-EGFR monoclonal antibody (mAb), NaGdF(4)-PEG-mAb nanoprobes were constructed, and their biocompatibility and binding specificity were evaluated through in vitro experiments. A series of in vivo experiments were then carried out for detecting intraperitoneal tumor xenografts in nude mice by using magnetic resonance (MR) imaging technique. The results revealed that the NaGdF(4)-PEG-mAb probes possessed satisfying tumor-specific targeting ability and strong MR contrast enhancement effects.

http://http://dx.doi.org/10.1021/nn304837c

Glu-RGD-bombesin (RGD-BBN) is a heterodimeric peptide that contains motifs recognizing both integrin α(v)β(3) and gastrin releasing peptide receptor (GRPR). We evaluated here (188)Re (t(1/2)=16.9 h) labeled RGD-BBN as a potential agent for radionuclide therapy of prostate cancer. RGD-BBN was conjugated with S-benzoylmercaptoacetylglycylglycyl (MAG(2)), and then labeled with (99m)Tc or (188)Re, respectively. The dual-receptor binding affinity of MAG(2)-RGD-BBN was investigated by a radioligand competition binding assay. Biodistribution study of (188)Re-MAG(2)-RGD-BBN was carried out in normal BALB/c mice and PC-3 human prostate tumor-bearing nude mice. Gamma imaging studies were performed in PC-3 tumor-bearing nude mice. Biodistribution in normal mice showed that both (99m)Tc and (188)Re-labeled MAG(2)-RGD-BBN possessed high pancreas uptake due to the high GRPR expression of this organ. Gamma imaging with both (99m)Tc and (188)Re-labeled RGD-BBN in PC-3 tumor-bearing nude mice demonstrated high tumor uptake. The PC-3 tumors were clearly visible at 1 postinjection, with high contrast to the contralateral background. The use of chelator MAG(2) enables successful and high-yield (99m)Tc and (188)Re radiolabeling of RGD-BBN with favorable tumor targeting specificity. Further optimization may allow potential clinical application of (188)Re-MAG(2)-RGD-BBN for tumor-targeted radionuclide therapy.

http://linkinghub.elsevier.com/retrieve/pii/S0969-8051(12)00276-4

PURPOSE:

Since their discovery in 2006, induced pluripotent stem cells (iPSCs) have gained increasing interest for tissue regeneration and transplantation therapies. However, teratoma formation after iPSC transplantation is one of the most serious drawbacks that may limit their further clinical application. We investigated here whether human iPSC-derived teratomas could be detected by an integrin-targeting agent (99m)Tc-PEG(4)-E[PEG(4)-c(RGDfK)](2) ((99m)Tc-3PRGD2).

METHODS:

Human-induced pluripotent stem cells (hiPSCs) were generated and characterized. In vitro integrin α(v)β(3) expression levels of hiPSC- and hiPSC-derived teratoma cells were determined by flow cytometry. (99m)Tc-3PRGD2 was prepared, and planar gamma imaging and biodistribution studies were carried out in teratoma-bearing severe combined immunodeficient (SCID) mice. Positron emission tomography (PET) imaging of teratomas with 2-deoxy-2-[(18)F]fluoro-D-glucose ((18)F-FDG) was also performed for comparison. Integrin α(v)β(3) expression in teratoma tissues was determined by immunofluorescence staining.

RESULTS:

(99m)Tc-3PRGD2 showed high (2.82 ± 0.21 and 2.69 ± 0.73%ID/g at 0.5 and 1 h pi, respectively) and specific (teratoma uptake decreased from 2.69 ± 0.73 to 0.53 ± 0.26%ID/g after blocking with cold 3PRGD2) uptake in teratoma tissues, and planar gamma imaging demonstrated the feasibility of noninvasively detecting the teratoma formation with (99m)Tc-3PRGD2. (18)F-FDG showed low teratoma uptake and thus failed to detect the teratomas. Ex vivo immunofluorescence staining validated the integrin α(v)β(3) expression in the vasculature during teratoma formation.

CONCLUSION:

Gamma imaging with (99m)Tc-3PRGD2 is a promising approach for the noninvasive monitoring of tumorigenicity after hiPSCs transplantation.

http://dx.doi.org/10.1007/s11307-012-0571-1

(99m)Tc-3PRGD2 is a new SPECT tracer targeting integrin α(V)β(3) receptor for detecting tumors, imaging angiogenesis, and evaluating tumor response to therapy. A multicenter study was designed to investigate the efficacy of (99m)Tc-3PRGD2 for the evaluation of patients with lung cancer.

METHODS:

Seventy patients (51 men, 19 women; mean age ± SD, 63 ± 9 y) with a suspected lung lesion and for whom definite pathologic diagnosis was finally obtained (malignant, n = 58; benign, n = 12) were recruited from 6 centers. Whole-body planar scanning and chest SPECT were performed at 1 and 4 h, respectively, after intravenous injection of 11.1 MBq/kg (0.3 mCi/kg) of (99m)Tc-3PRGD2. The images were read in consensus by 6 experienced nuclear medicine physicians masked to the source, history, and pathologic diagnosis. The tumor-to-background (T/B) ratios were calculated for semiquantitative analysis. A Student t test was used for statistical analysis, and a P value less than 0.05 was considered significant.

RESULTS:

With low (99m)Tc-3PRGD2 background in the lungs and mediastinum, most lung malignancies were prominent on the 1-h images (T/B ratio, 1.65 ± 0.47 for the planar imaging and 2.78 ± 1.52 for SPECT). The T/B ratios were significantly lower in the benign lesions (P < 0.05). The sensitivity was 88% for semiquantitative analysis and could reach 93%-97% in visual analysis when considering the volume effect, necrosis, and metastasis. However, the specificity was only 58%-67%. Most lymph node and bone metastases could also be detected.

CONCLUSION:

(99m)Tc-3PRGD2 imaging at 1 h is sensitive for the detection of lung cancer, meriting further investigation of (99m)Tc-3PRGD2 as a novel clinical tracer for integrin receptor imaging.

http://dx.doi.org/10.2967/jnumed.111.098988

Targeting radiopeptides are promising agents for radio-theranostics. However, in vivo evaluation of their targeting specificity is often obscured by their short biologic half-lives and low binding affinities. Here, we report an approach to efficiently examine targeting radiopeptides with a new class of octavalent peptide fluorescent nanoprobe (Octa-FNP) platform, which is composed of candidate targeting peptides and a tetrameric far-red fluorescent protein (tfRFP) scaffold. To shed light on this process, (125)I-Octa-FNP, (125)I-tfRFP and (125)I-peptide were synthesized, and their targeting functionalities were compared. Both fluorescence imaging and radioactive quantification results confirmed that (125)I-Octa-FNP had a significantly higher cellular binding capability than (125)I-tfRFP. In vivo biodistribution studies show that at 6 h post-injection, (125)I-Octa-FNP had 2-fold and 30-fold higher tumor uptake than that of (125)I-tfRFP and (125)I-peptide, respectively. Moreover, γ-imaging at 24 h post-injection revealed a remarkable accumulation of (125)I-Octa-FNP in the tumor while maintaining an extremely low background contrast, which was further confirmed by immunofluorescence analysis. These data suggested that, as an engineered and multivalent platform, Octa-FNP could enhance the tumor targeting of a designed peptide and provide excellent contrast radioimaging, making it a valuable tool for the evaluation of the targeting ability of specifically designed radiopeptides for cancer theranostics.

http://dx.doi.org/10.1016/j.biomaterials.2012.03.0

Glu-RGD-bombesin (RGD-BBN) is a heterodimeric peptide that contains motifs recognizing both integrin α(v)β(3) and gastrin releasing peptide receptor (GRPR). We evaluated here (188)Re (t(1/2)=16.9 h) labeled RGD-BBN as a potential agent for radionuclide therapy of prostate cancer. RGD-BBN was conjugated with S-benzoylmercaptoacetylglycylglycyl (MAG(2)), and then labeled with (99m)Tc or (188)Re, respectively. The dual-receptor binding affinity of MAG(2)-RGD-BBN was investigated by a radioligand competition binding assay. Biodistribution study of (188)Re-MAG(2)-RGD-BBN was carried out in normal BALB/c mice and PC-3 human prostate tumor-bearing nude mice. Gamma imaging studies were performed in PC-3 tumor-bearing nude mice. Biodistribution in normal mice showed that both (99m)Tc and (188)Re-labeled MAG(2)-RGD-BBN possessed high pancreas uptake due to the high GRPR expression of this organ. Gamma imaging with both (99m)Tc and (188)Re-labeled RGD-BBN in PC-3 tumor-bearing nude mice demonstrated high tumor uptake. The PC-3 tumors were clearly visible at 1 postinjection, with high contrast to the contralateral background. The use of chelator MAG(2) enables successful and high-yield (99m)Tc and (188)Re radiolabeling of RGD-BBN with favorable tumor targeting specificity. Further optimization may allow potential clinical application of (188)Re-MAG(2)-RGD-BBN for tumor-targeted radionuclide therapy.

http://de.doi.org/10.1016/j.nucmedbio.2012.11.002

We report the design, synthesis and biological evaluation of a novel (99m)Tc 4-(4-cyclohexylpiperazine-1-yl)-butan-1-one-1-cyclopentadienyltricarbonyl technetium ([(99m)Tc]5) as a potential SPECT tracer for imaging of σ(2) receptors in tumors. [(99m)Tc]5 was prepared in 25±5% isolated radiochemical yield with radiochemical purity of >99% via double-ligand transfer (DLT) reaction from the ferrocene precursor 2b (4-(4-cyclohexylpiperazine-1-yl)-1-ferrocenylbutan-1-one). The corresponding Re-complex 4 and the ferrocenyl complex 2b showed relatively high affinity towards σ(2) receptors in in vitro competition binding assay (K(i) values of 4 and 2b were 64.4±18.5 nM and 43.6±21.3 nM, respectively) and moderate to high selectivity versus σ(1) receptors (K(i)σ(1)/K(i)σ(2) ratios were 12.5 and 95.5, respectively). The logD value of [(99m)Tc]5 was determined to be 2.52±0.33. Biodistribution studies in mice revealed comparably high initial brain uptake of [(99m)Tc]5 and slow washout. Administration of haloperidol 5 min prior to injection of [(99m)Tc]5 significantly reduced the radiotracer uptake in brain, heart, lung, and spleen by 40-50% at 2h p.i.. Moreover, [(99m)Tc]5 showed high uptake in C6 glioma cell lines (8.6%) after incubation for 1h. Blocking with haloperidol to compete with [(99m)Tc]5 significantly reduced the cell uptake. Preliminary blocking study in C6-brain-tumor bearing rats showed that [(99m)Tc]5 binds to σ receptors in the brain-tumor specifically. These results are encouraging for further exploration of (99m)Tc-labeled probes for σ(2) receptor tumor imaging in vivo.

Copyright © 2012 Elsevier Ltd. All rights reserved.

http://dx.doi.org/10.1016/j.bmcl.2010.08.083

Dextran graft poly (N-methacryloylglycylglycine) copolymer-tyrosine conjugates (dextran-g-PMAGGCONHTyr) were synthesized and characterized. Dynamic light scattering (DLS) results indicated that the graft copolymers are soluble in pH 7.4 PBS and 0.9% saline solutions. The graft copolymers were labeled with (125)I, and the labeling stability in 0.9% saline solution was investigated. Pharmacokinetics studies showed a rapid clearance of (125)I-labeled graft copolymers from the blood pool. Biodistribution images confirmed the preferable liver and spleen accumulation within 1 h after injection and rapid clearance from all the organs over time. The graft copolymer with molecular weight of 9.8 kDa was eliminated from the kidney significantly faster than those with higher molecular weight. The effect of the numbers of -COOH groups on the graft copolymers on the biodistribution was also investigated. It was found that the graft copolymers with the average number of -COOH groups per glucopyranose unit (DS(-COOH)) of 0.57 and 0.18 are mainly distributed in liver and spleen at 1 h after injection, whereas the graft copolymer with DS(-COOH) of 0.07 is mainly accumulated in kidney.

http://dx.doi.org/10.1021/bm200194s

Targeted radionuclide therapy, which is based on the selective delivery of a sufficient radiation dose to tumors without significantly affecting normal tissues, is a promising therapeutic approach for the treatment of a wide variety of malignancies. Integrins, a family of cell adhesion molecules, play key roles during tumor angiogenesis and metastasis. Among all the integrins, αvβ3 seems to be the most important in the process of tumor angiogenesis. Integrin αvβ3 is highly expressed on activated endothelial cells, new-born vessels as well as some tumor cells, but is not present in resting endothelial cells and most normal organ systems, making it a suitable target for anti-tumor therapy. In this review, we summarize the current development and applications of antibody-, peptide-, and other ligand-based integrin targeted radiotherapeutics for tumor radiation therapy.

http://www.ncbi.nlm.nih.gov/pmc/articles/pmid/21547160/

Positron emission tomography (PET) has become a powerful tool for probing biochemical processes in living subjects. PET imaging depends largely on the development of novel PET tracers labeled with positron-emitting radionuclides. Since the four traditional PET isotopes (18F, 11C, 13N, and 15O) are produced in a cyclotron and are short-lived, their use for long-term observation of biological processes in vivo is limited. In the last decades, extensive research in the development of other unconventional radionuclides (such as 64Cu, 68Ga, 89Zr, 86Y, and 124I) labeled tracers with half-lives complementary to the biological properties of their targeting agents has been conducted. Among these tracers, 86Y-based PET tracers have gained increasing attention since they are ideal surrogates for in vivo determination of biodistribution and dosimetry of therapeutic 90Y (pure β - emitter) pharmaceuticals. In this review article, we will brief introduce the physical characteristics, production, and radiochemistry of 86Y, and will summarize the current 86Y-based PET tracers used for molecular imaging and cancer detection in animal studies and in clinical trials.

http://www.eurekaselect.com/94484/article

Early evaluation of cancer response to a therapeutic regimen can help increase the effectiveness of treatment schemes and, by enabling early termination of ineffective treatments, minimize toxicity, and reduce expenses. Biomarkers that provide early indication of tumor therapy response are urgently needed. Solid tumors require blood vessels for growth, and new anti-angiogenic agents can act by preventing the development of a suitable blood supply to sustain tumor growth. The purpose of this study is to develop a class of novel molecular imaging probes that will predict tumor early response to an anti-angiogenic regimen with the humanized vascular endothelial growth factor antibody bevacizumab. Using a bevacizumab-sensitive LS174T colorectal cancer model and a 12-mer bacteriophage (phage) display peptide library, a bevacizumab-responsive peptide (BRP) was identified after six rounds of biopanning and tested in vitro and in vivo. This 12-mer peptide was metabolically stable and had low toxicity to both endothelial cells and tumor cells. Near-infrared dye IRDye800-labeled BRP phage showed strong binding to bevacizumab-treated tumors, but not to untreated control LS174T tumors. In addition, both IRDye800- and (18)F-labeled BRP peptide had significantly higher uptake in tumors treated with bevacizumab than in controls treated with phosphate-buffered saline. Ex vivo histopathology confirmed the specificity of the BRP peptide to bevacizumab-treated tumor vasculature. In summary, a novel 12-mer peptide BRP selected using phage display techniques allowed non-invasive visualization of early responses to anti-angiogenic treatment. Suitably labeled BRP peptide may be potentially useful pre-clinically and clinically for monitoring treatment response.

http://dx.doi.org/10.1007/s00726-010-0548-9

PURPOSE:

(99m)Tc-3PRGD(2) is a (99m)Tc-labeled dimeric cyclic RGD peptide with increased receptor binding affinity and improved kinetics for in vivo imaging of integrin α(v)β(3) expression in nude mouse model. To accelerate its clinical translation, we reported here the evaluation of the kit-formulated (99m)Tc-3PRGD(2) in healthy cynomolgus primates for its blood clearance kinetics, biodistribution, and radiation dosimetry.

PROCEDURES:

Healthy cynomolgus primates (4.1 ± 0.7 kg, n = 5) were anesthetized, and the venous blood samples were collected via a femoral vein catheter at various time points after injection of ~555 MBq of (99m)Tc-3PRGD(2). Serial whole-body scans were performed with a dual-head single photon emission computed tomography system after administering ~555 MBq of (99m)Tc-3PRGD(2) in the non-human primates, and the radiation dosimetry estimate was calculated.

RESULTS:

(99m)Tc-3PRGD(2) could be easily obtained from freeze-dried kits with high radiochemical purity (>95%) and high specific activity (~5 Ci/μmol). (99m)Tc-3PRGD(2) had a rapid blood clearance with less than 1% of the initial radioactivity remaining in the blood circulation at 60 min postinjection. No adverse reactions were observed up to 4 weeks after the repeated dosing. The whole-body images exhibited high kidney uptake of (99m)Tc-3PRGD(2) and high radioactivity accumulation in the bladder, demonstrating the rapid renal clearance of this tracer. The highest radiation doses of (99m)Tc-3PRGD(2) were found in the kidneys (13.2 ± 1.08 μGy/MBq) and the bladder wall (33.1 ± 1.91 μGy/MBq).

CONCLUSION:

(99m)Tc-3PRGD(2) can be readily available using the kit formulation. This tracer is safe and well tolerated, and no adverse events occurred in non-human primates. Further clinical testing and translation of (99m)Tc-3PRGD(2) for noninvasive imaging of integrin α(v)β(3) in humans are warranted.

http://dx.doi.org/10.1007/s11307-010-0385-y

We have recently developed a series of new Arg-Gly-Asp (RGD) dimeric peptides for specific targeting of integrin α(v)β₃ with enhanced tumor uptake and improved pharmacokinetics. In this study, we investigated ⁹⁰Y-labeled RGD tetramer (RGD4) and the new type of RGD dimer (3PRGD2), for the radionuclide therapy of integrin α(v)β₃-positive tumors. Biodistribution and gamma imaging studies of ¹¹¹In labeled RGD4 and 3PRGD2 were performed. Groups of nude mice were used to determine maximum tolerated dose (MTD) of ⁹⁰Y-DOTA-RGD4 and ⁹⁰Y-DOTA-3PRGD2. The radionuclide therapeutic efficacy of ⁹⁰Y-DOTA-RGD4 and ⁹⁰Y-DOTA-3PRGD2 was evaluated in U87MG tumor-bearing nude mice. The U87MG tumor uptake of ¹¹¹In-DOTA-3PRGD2 was slightly lower than that of the ¹¹¹In-DOTA-RGD4 (e.g., 6.13 ± 0.82%ID/g vs 6.43 ± 1.6%ID/g at 4 h postinjection), but the uptake of ¹¹¹In-DOTA-3PRGD2 in normal organs, such as liver and kidneys, was much lower than that of ¹¹¹In-DOTA-RGD4, which resulted in much higher tumor-to-nontumor ratios and lower toxicity. The MTD of ⁹⁰Y-DOTA-RGD4 in nude mice is less than 44.4 MBq, while the MTD of ⁹⁰Y-DOTA-3PRGD2 in mice is more than 55.5 MBq. ⁹⁰Y-DOTA-3PRGD2 administration exhibited a similar tumor inhibition effect as compared with ⁹⁰Y-DOTA-RGD4 at the same dose. The tumor vasculature in the ⁹⁰Y-DOTA-3PRGD2 treatment group was much less than the control groups. Radionuclide therapy studies exhibited that both ⁹⁰Y-DOTA-RGD4 and ⁹⁰Y-DOTA-3PRGD2 caused significant tumor growth delay in the U87MG tumor model. Compared to ⁹⁰Y-DOTA-RGD4, the low accumulation of ⁹⁰Y-DOTA-3PRGD2 in normal organs led to lower toxicity and higher MTD in nude mice, which would make it more suitable for high dose or multiple-dose regimens, in order to achieve maximum therapeutic efficacy.

http://dx.doi.org/10.1021/mp100403y

Dextran graft poly (N-methacryloylglycylglycine) copolymer-tyrosine conjugates (dextran-g-PMAGGCONHTyr) were synthesized and characterized. Dynamic light scattering (DLS) results indicated that the graft copolymers are soluble in pH 7.4 PBS and 0.9% saline solutions. The graft copolymers were labeled with (125)I, and the labeling stability in 0.9% saline solution was investigated. Pharmacokinetics studies showed a rapid clearance of (125)I-labeled graft copolymers from the blood pool. Biodistribution images confirmed the preferable liver and spleen accumulation within 1 h after injection and rapid clearance from all the organs over time. The graft copolymer with molecular weight of 9.8 kDa was eliminated from the kidney significantly faster than those with higher molecular weight. The effect of the numbers of -COOH groups on the graft copolymers on the biodistributionwas also investigated. It was found that the graft copolymers with the average number of -COOH groups per glucopyranose unit (DS(-COOH)) of 0.57 and 0.18 are mainly distributed in liver and spleen at 1 h after injection, whereas the graft copolymer with DS(-COOH) of 0.07 is mainly accumulatedin kidney.

http://dx.doi.org/10.1021/bm200194s

PURPOSE:

Targeting of integrin α(ν)β(3) with molecular imaging agents offers great potential in early detection and monitoring of tumour angiogenesis. Recently, an RGD (Arg-Gly-Asp) tracer, (99m)Tc-3P(4)-RGD(2), with high affinity to integrin α(ν)β(3) and in vivo tumour uptake was developed. In this study, we evaluate the feasibility of this novel radiotracer in the noninvasive differentiation of solitary pulmonary nodules (SPNs).

METHODS:

Twenty-one patients with SPNs on CT were studied scintigraphically after administration of (99m)Tc-3P(4)-RGD(2) with a dose of 939 ±  118 MBq. Image interpretation using a 5-point scale was performed by one thoracic radiologist for CT and three nuclear medicine radiologists for single photon emission computed tomography (SPECT). Scintigraphic images were also analysed semiquantitatively by calculating tumour to normal tissue ratio (T/N). The "gold standard" was based on the histopathological diagnosis of the surgical samples from all recruited patients. A fraction of the samples were analysed immunohistochemically for integrin α(v)β(3) expression.

RESULTS:

Among the 21 SPNs, 15 (71%) were diagnosed as malignant and 6 (29%) were benign. The mean size for SPNs was 2.2 ±  0.6 cm. The sensitivity and specificity for CT interpretation, SPECT visual and semiquantitative analysis were 80/67%, 100/67% and 100/67%, respectively. All SPNs classified as indeterminate by CT were correctly diagnosed by (99m)Tc-3P(4)-RGD(2) scintigraphy. The empirical receiver-operating characteristic (ROC) areas were 0.811 [95% confidence interval (CI) 58-95%] for CT, 0.833 (95% CI 61-96%) for SPECT and 0.844 (95% CI 62-96%) for T/N ratios, respectively. Immunohistochemistry confirmed α(ν)β(3) expression in malignant and benign nodules with uptake in (99m)Tc-3P(4)-RGD(2) scintigraphy.

CONCLUSION:

In this first-in-human study, we demonstrated the feasibility of using (99m)Tc-3P(4)-RGD(2) scintigraphy in differentiating SPNs. This procedure appears to be highly sensitive in detection of malignant SPNs. SPECT visual analysis seems to be sufficient for characterization of SPNs.

http://dx.doi.org/10.1007/s00259-011-1901-2

The peptide bombesin (BN) and derivates thereof show high binding affinity for the gastrin-releasing peptide receptor (GRPR), which is highly expressed in primary and metastasized prostate cancer. We have synthesized a new BN-based radiopharmaceutical (99m)technetium-HYNIC(tricine/TPPTS)-Aca-BN(7-14) ((99m)Tc-HABN) and evaluated its GRPR targeting properties in vitro and in a xenograft tumor model for humanprostate cancer in athymic mice. (99m)Tc-HABN was synthesized, and its lipophilicity and stability were investigated. The IC(50), internalization and efflux properties were determined in vitro using the GRPR expressing human prostate cancer cell line PC-3. (99m)Tc-HABN biodistribution andmicroSPECT imaging were performed in PC-3 tumor-bearing athymic mice. (99m)Tc-HABN was prepared with high labeling yield (>90%), high radiochemical purity (>95%) and a specific activity of ~19.8 MBq/nmol. The partition coefficient log D value was -1.60 ± 0.06. (99m)Tc-HABN proved to be stable in human serum for 6 h. The IC50 of HYNIC-Aca-BN(7-14) was 12.81 ± 0.14 nM. Incubation of PC-3 cells with (99m)Tc-HABN demonstrated rapid cellular internalization and a long intracellular retention time. When mice were injected with (99m)Tc-HABN, the activity was predominantly cleared via the kidneys. Uptake in the tumor was 2.24 ± 0.64% ID/g after 30 min, with a steady decrease during the 4 h study period. In vivo experiments with a blocking agent showed GRPR mediated uptake. (99m)Tc-HABN microSPECT imaging resulted in clear delineation of the tumor. (99m)Tc-HABN is a novel BN-based radiopharmaceutical that proved to be suitable for targeted imaging of prostate cancer with microSPECT using the human prostate cancer cell line PC-3 in a xenograft mouse model.

http://dx.doi.org/10.1021/mp200014h

The purpose of this study was to noninvasively monitor the therapeutic efficacy of cyclophosphamide (CTX) in a mouse model by dual-modalitymolecular imaging: positron emission tomography (PET) and bioluminescence imaging (BLI). Firefly luciferase (fLuc) transfected HCC-LM3-fLuc human hepatocellular carcinoma cells were injected subcutaneously into BALB/c nude mice to establish the experimental tumor model. Two groups of HCC-LM3-fLuc tumor-bearing mice (n  =  7 per group) were treated with saline or CTX (100 mg/kg on days 0, 2, 5, and 7). BLI and (18)F-fluorodeoxyglucose ((18)F-FDG) PET scans were done to evaluate the treatment efficacy. CTX induced a 25.25 ± 13.13% and 35.91 ± 25.85% tumorgrowth inhibition rate on days 9 and 12 posttreatment, respectively, as determined by BLI. A good linear correlation was found between the tumorsizes measured by caliper and the BLI signals determined by optical imaging (R(2)  =  .9216). (18)F-FDG imaging revealed a significant uptake reduction in the tumors of the CTX-treated group compared to that in the saline control group (5.30 ± 1.97 vs 3.00 ± 2.11% ID/g) on day 16 after CTX treatment. Dual-modality molecular imaging using BLI and small-animal PET can play important roles in the process of chemotherapy and will provide noninvasive and reliable monitoring of the therapeutic response.

http://dx.doi.org/10.2310/7290.2010.00041

Radiolabeled cyclic RGD (Arg-Gly-Asp) peptides represent a new class of radiotracers with potential for early tumor detection and noninvasive monitoring of tumor metastasis and therapeutic response in cancer patients. This article describes the synthesis of two cyclic RGD peptide dimer conjugates, DOTA-PEG(4)-E[PEG(4)-c(RGDfK)](2) (DOTA-3PEG(4)-dimer: DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid; PEG(4) = 15-amino-4,7,10,13-tetraoxapentadecanoic acid) and DOTA-G(3)-E[G(3)-c(RGDfK)](2) (DOTA-3G(3)-dimer: G(3) = Gly-Gly-Gly). Integrin alpha(v)beta(3) binding affinities of cyclic RGD peptides were determined by competitive displacement of (125)I-echistatin bound to U87MG human glioma cells and follow the order of DOTA-E{E[c(RGDfK)](2)}(2) (DOTA-tetramer: IC(50) = 10 +/- 2 nM) > DOTA-3G(3)-dimer (IC(50) = 62 +/- 6 nM) approximately DOTA-3PEG(4)-dimer (IC(50) = 74 +/- 3 nM) > DOTA-E[c(RGDfK)](2) (DOTA-dimer: IC(50) = 102 +/- 5 nM). The addition of PEG(4) and G(3) linkers between two cyclic RGD motifs in DOTA-3G(3)-dimer and DOTA-3PEG(4)-dimer makes it possible for them to achieve the simultaneous integrin alpha(v)beta(3) binding in a bivalent fashion. Both (64)Cu(DOTA-3PEG(4)-dimer) and (64)Cu(DOTA-3G(3)-dimer) were prepared in high yield with specific activity being >50 Ci/mmol. Biodistribution and imaging studies were performed in athymic nude mice bearing U87MG human glioma xenografts. The results from those studies show that PEG(4) and G(3) linkers are particularly useful for improving tumor uptake and clearance kinetics of (64)Cu radiotracers from the nontumor organs, such as kidneys, liver, and lungs. There is a linear relationship between the tumor size and %ID tumor uptake, suggesting that (64)Cu(DOTA-3PEG(4)-dimer) and (64)Cu(DOTA-3PEG(4)-dimer) might be useful for noninvasive monitoring of tumor growth or shrinkage during antiangiogenic therapy. MicroPET imaging data clearly demonstrate the utility of (64)Cu(DOTA-3G(3)-dimer) as a new PET radiotracer for imaging integrin alpha(v)beta(3)-positive tumors.http://dx.doi.org/10.1007/s00726-009-0439-0

Porphyrin based photosensitizers are useful agents for photodynamic therapy (PDT) and fluorescence imaging of cancer. Porphyrins are also excellent metal chelators forming highly stable metallo-complexes making them efficient delivery vehicles for radioisotopes. Here we investigated the possibility of incorporating (64)Cu into a porphyrin-peptide-folate (PPF) probe developed previously as folate receptor (FR) targeted fluorescent/PDTagent, and evaluated the potential of turning the resulting (64)Cu-PPF into a positron emission tomography (PET) probe for cancer imaging. Noninvasive PET imaging followed by radioassay evaluated the tumor accumulation, pharmacokinetics and biodistribution of (64)Cu-PPF. (64)Cu-PPF uptake in FR-positive tumors was visible on small-animal PET images with high tumor-to-muscle ratio (8.88 ± 3.60) observed after 24 h. Competitive blocking studies confirmed the FR-mediated tracer uptake by the tumor. The ease of efficient (64)Cu-radiolabeling of PPF while retaining its favorable biodistribution, pharmacokinetics and selective tumor uptake, provides a robust strategy to transform tumor-targeted porphyrin-based photosensitizers into PET imaging probes.

http://www.thno.org/v01p0363.htm

PURPOSE:

The purpose of this study was to demonstrate the valence of cyclic RGD peptides, P-RGD (PEG(4)-c(RGDfK): PEG(4) = 15-amino-4,710,13-tetraoxapentadecanoic acid), P-RGD(2) (PEG(4)-E[c(RGDfK)](2), 2P-RGD(4) (E{PEG(4)-E[c(RGDfK)](2)}(2), 2P4G-RGD(4) (E{PEG(4)-E[G(3)-c(RGDfK)](2)}(2): G(3) = Gly-Gly-Gly) and 6P-RGD(4) (E{PEG(4)-E[PEG(4)-c(RGDfK)](2)}(2)) in binding to integrin α(v)β(3), and to assess the impact of peptide and linker multiplicity on biodistribution properties, excretion kinetics and metabolic stability of their corresponding (111)In radiotracers.

METHODS:

Five new RGD peptide conjugates (DOTA-P-RGD (DOTA =1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracetic acid), DOTA-P-RGD(2), DOTA-2P-RGD(4), DOTA-2P4G-RGD(4), DOTA-6P-RGD(4)), and their (111)In complexes were prepared. The integrin α(v)β(3) binding affinity of cyclic RGD conjugates were determined by a competitive displacement assay against (125)I-c(RGDyK) bound to U87MG human glioma cells. Biodistribution, planar imaging and metabolism studies were performed in athymic nude mice bearing U87MG human glioma xenografts.

RESULTS:

The integrin α(v)β(3) binding affinity of RGD conjugates follows the order of: DOTA-6P-RGD(4) (IC(50) = 0.3 ± 0.1 nM) ~ DOTA-2P4G-RGD(4) (IC(50) = 0.2 ± 0.1 nM) ~ DOTA-2P-RGD(4) (IC(50) = 0.5 ± 0.1 nM) > DOTA-3P-RGD(2) (DOTA-PEG(4)-E[PEG(4)-c(RGDfK)](2): IC(50) = 1.5 ± 0.2 nM) > DOTA-P-RGD(2) (IC(50) = 5.0 ± 1.0 nM) >> DOTA-P-RGD (IC(50) = 44.3 ± 3.5 nM) ~ c(RGDfK) (IC(50) = 49.9 ± 5.5 nM) >> DOTA-6P-RGK(4) (IC(50) = 437 ± 35 nM). The fact that DOTA-6P-RGK(4) had much lower integrin α(v)β(3) binding affinity than DOTA-6P-RGD(4) suggests that the binding of DOTA-6P-RGD(4) to integrin α(v)β(3) is RGD-specific. This conclusion is consistent with the lower tumor uptake for (111)In(DOTA-6P-RGK(4)) than that for (111)In(DOTA-6P-RGD(4)). It was also found that the G(3) and PEG(4) linkers between RGD motifs have a significant impact on the integrin α(v)β(3)-targeting capability, biodistribution characteristics, excretion kinetics and metabolic stability of (111)In-labeled cyclic RGDpeptides.

CONCLUSION:

On the basis of their integrin α(v)β(3) binding affinity and tumor uptake of their corresponding (111)In radiotracers, it was conclude that 2P-RGD(4), 2P4G-RGD(4) and 6P-RGD(4) are most likely bivalent in binding to integrin α(v)β(3), and extra RGD motifs might contribute to the longtumor retention times of (111)In(DOTA-2P-RGD(4)),( 111)In(DOTA-2P4G-RGD(4)) and (111)In(DOTA-6P-RGD(4)) than that of (111)In(DOTA-3P-RGD(3)) at 72 h p.i. Among the (111)In-labeled cyclic RGD tetramers evaluated in the glioma model, (111)In(DOTA-2P4G-RGD(4)) has very high tumoruptake with the best tumor/kidney and tumor/liver ratios, suggesting that (90)Y(DOTA-2P4G-RGD(4)) and (177)Lu(DOTA-2P4G-RGD(4)) might have the potential for targeted radiotherapy of integrin α(v)β(3)-positive tumors.

http://www.thno.org/v01p0322.htm

PURPOSE:

In vivo imaging of α(v)β(3) has important diagnostic and therapeutic applications. (18)F-Galacto-arginine-glycine-aspartic acid (RGD) has been developed for positron emission tomography (PET) imaging of integrin α(v)β(3) expression and is now being tested on humans. Dimerization and multimerization of cyclic RGD peptides have been reported to improve the integrin α(v)β(3)-binding affinity due to the polyvalency effect. Here, we compared a number of new dimeric RGD peptide tracers with the clinically used (18)F-galacto-RGD.

PROCEDURES:

RGD monomers and dimers were coupled with galacto or PEG(3) linkers, and labeled with (18)F using 4-nitrophenyl 2-(18)F-fluoropropionate ((18)F-NFP) or N-succinimidyl 4-(18)F-fluorobenzoate as a prosthetic group. The newly developed tracers were evaluated by cell-based receptor-binding assay, biodistribution, and small-animal PET studies in a subcutaneous U87MG glioblastoma xenograft model.

RESULTS:

Starting with (18)F-F(-), the total reaction time for (18)F-FP-SRGD2 and (18)F-FP-PRGD2 is about 120 min. The decay-corrected radiochemical yields for (18)F-FP-SRGD2 and (18)F-FP-PRGD2 are 52 ± 9% and 80 ± 7% calculated from (18)F-NFP. Noninvasive small-animal PET and direct tissue sampling experiments demonstrated that the dimeric RGD peptides had significantly higher tumor uptake as compared to (18)F-galacto-RGD.

CONCLUSION:

Dimeric RGD peptide tracers with relatively high tumor integrin-specific accumulation and favorable in vivo kinetics may have the potential to be translated into clinic for integrin α(v)β(3) imaging.

http://dx.doi.org/10.1007/s11307-009-0284-2

Integrin alphavbeta3 plays great roles in tumor angiogenesis, invasion, and metastasis. We report here the noninvasive visualization of tumor integrin alphavbeta3 expression by using near-infrared fluorescence (NIRF) imaging of an IRDye800-labeled new cyclic RGD (arginine-glycine-aspartic acid)dimer with tetra(ethylene glycol) (PEG4) linkers (ie, E[PEG4-c(RGDfK)]2, PEG4 = 15-amino-4,7,10,13-tetraoxapentadecanoic acid) in a U87MG tumor model. Fluorescent dye-labeled E[PEG4-c(RGDfK)]2 were subjected to in vitro cell staining, in vivo NIRF imaging, ex vivo NIRF imaging, and histologic studies. The in vitro and in vivo characterization of dye-labeled E[PEG4-c(RGDfK)]2 were compared with dye-labeled RGD dimer without PEG4 linkers (namely, E[c(RGDfK)]2). Both Cy5.5-E[PEG4-c(RGDfK)]2 and Cy5.5-E[c(RGDfK)]2 exhibited integrin alphavbeta3 binding specificity in a cell-staining experiment. In vivo NIRF imaging showed higher tumor accumulation and tumor to background contrast of IRDye800-E[PEG4-c(RGDfK)]2 over IRDye800-E[c(RGDfK)]2. The tumor integrin alphavbeta3 specificity of IRDye800-E[PEG4-c(RGDfK)]2 was confirmed by successful inhibition of tumor uptake in the presence of an excess dose of c(RGDfK). Histologic examination revealed both tumor vasculature and tumor cellintegrin alphavbeta3 binding of IRDye800-E[PEG4-c(RGDfK)]2 in vivo. In summary, NIRF imaging with IRDye800-E[PEG4-c(RGDfK)]2 offers an easy, fast, and low-cost way to detect and semiquantify tumor integrin alphavbeta3 expression in living subjects.http://dx.doi.org/10.2310/7290.2009.00032

Radioimmunotherapy (RIT) is a promising approach for the treatment of a wide variety of malignancies. The aim of this study was to investigate the therapeutic efficacy of (131)I-labeled anticarcinoembryonic antigen (CEA) monoclonal antibody CL58 in a human colon cancer mouse model. In vitro and in vivo characteristics of (125)I-CL58 were evaluated in LS180 human colon cancer cells and the nude mouse model. (131)I-CL58 was prepared and its in vivo therapeutic efficacy was tested. (125)I-CL58 showed high affinity to LS180 cells, as well as high tumor uptake and long tumor retention in LS180 tumor xenografts. (131)I-CL58 exhibited dose-dependent inhibition of LS180 tumor growth. With the excellent in vitro and in vivo characteristics, and the effective therapy for colon cancer in animal model, (131)I-CL58 is a promising agent for RIT of CEA-positive tumors including colon cancer.

In this study, we reported the preparation and evaluation of (177)Lu-DOTA-RGD2, (177)Lu-DOTA-Bz-RGD2 and (177)Lu-DTPA-Bz-RGD2 (RGD2 = E[c(RGDfK)](2)) as a potential therapeutic radiotracers for the treatment of integrin alpha(v)beta(3)-positive tumors. The BALB/c nude mice bearing the U87MG human glioma xenografts were used to evaluate the biodistribution characteristics and excretion kinetics of (177)Lu-DOTA-RGD2, (177)Lu-DOTA-Bz-RGD2 and (177)Lu-DTPA-Bz-RGD2. It was found that there were no major differences in their lipophilicity and biodistribution characteristics, particularly at latter time points. A major advantage of using DTPA-Bz as the bifunctional chelator (BFC) was its high radiolabeling efficiency (fast and high yield radiolabeling) at room temperature. Using DOTA and DOTA-Bz as BFCs, the radiolabeling kinetics was slow, and heating at 100 degrees C and higher DOTA-conjugate concentration were needed for successful (177)Lu-labeling. Therefore, DTPA-Bz is an optimal BFC for routine preparationof (177)Lu-labeled cyclic RGDfK peptides, and (177)Lu-DTPA-Bz-RGD2 is worthy of further investigation for targeted radiotherapy of integrin alpha(v)beta(3)-positive tumors.

This report presents the synthesis and evaluation of (111)In(DOTA-6G-RGD(4)) (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracetic acid; 6G-RGD(4) = E{G(3)-E[G(3)-c(RGDfK)](2)}(2) and G(3) = Gly-Gly-Gly), (111)In(DOTA-RGD(4)) (RGD(4) = E{E[c(RGDfK)](2)}(2)) and (111)In(DOTA-3G-RGD(2)) (3G-RGD(2) = G(3)-E[G(3)-c(RGDfK)](2)) as new radiotracers for imaging integrin alpha(v)beta(3)-positive tumors. The IC(50) values of DOTA-6G-RGD(4), DOTA-RGD(4), and DOTA-3G-RGD(2) were determined to be 0.4 +/- 0.1, 1.4 +/- 0.1 and 1.1 +/- 0.1 nM against (125)I-c(RGDyK) bound to integrin alpha(v)beta(3)-positive U87MG human glioma cells. (111)In(DOTA-6G-RGD(4)), (111)In(DOTA-RGD(4)), and (111)In(DOTA-3G-RGD(2)) were prepared by reacting (111)InCl(3) with the respective DOTA conjugate in NH(4)OAc buffer (100 mM, pH = 5.5). Radiolabeling could be completed by heating the reaction mixture at 100 degrees C for 15-20 min. The specific activity was approximately 1850 MBq/micromol for (111)In(DOTA-3G-RGD(2)) and approximately 1480 MBq/micromol for (111)In(DOTA-6G-RGD(4)). The athymic nude mice bearing U87MG human glioma xenografts were used to evaluate tumor uptake and excretion kinetics of (111)In(DOTA-6G-RGD(4)), (111)In(DOTA-RGD(4)), and (111)In(DOTA-3G-RGD(2)). The results from both the integrin alpha(v)beta(3) binding assay and biodistribution studies suggest that the tetrameric cyclic RGD peptides, such as RGD(4) and 6G-RGD(4), are most likely bivalent in binding to the integrin alpha(v)beta(3). Both (111)In(DOTA-6G-RGD(4)) and (111)In(DOTA-RGD(4)) had significantly higher tumor uptake than (111)In(DOTA-3G-RGD(2)) at 24-72 h postinjection due to the extra RGD motifs in RGD(4) and 6G-RGD(4). (111)In(DOTA-3G-RGD(2)) had very little metabolism, while (111)In(DOTA-6G-RGD(4)) had significant metabolism during its excretion via both renal and hepatobiliary routes over the 2 h period, probably due to its much larger size. The combination of high tumor uptake with long tumor retention suggests that their corresponding (90)Y and (177)Lu analogues M(DOTA-6G-RGD(4)) (M = (90)Y and (177)Lu) might be useful as therapeutic radiotracers for treatment of integrin alpha(v)beta(3)-positive solid tumors.

Panitumumab (ABX-EGF or Vectibix), the first fully human monoclonal antibody targeting epidermal growth factor receptor (EGFR), was approved by the Food and Drug Administration for treatment of patients with metastatic colorectal cancer. Here, we report for the first time the radioimmunotherapy(RIT) of EGFR-positive human head and neck cancer in a nude mouse model using pure beta(-) emitter (90)Y-labeled panitumumab. Biodistribution and planar gamma-imaging studies were carried out with (111)In-DOTA-panitumumab. The RIT efficacy of (90)Y-DOTA-panitumumab was evaluated in UM-SCC-22B tumor model. CD31, Ki67, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, and H&E staining were done on UM-SCC-22B tumor sections after treatment. The tumor uptake of (111)In-DOTA-panitumumab in UM-SCC-22B tumor-bearing nude mice was 26.10 +/- 4.93, 59.11 +/- 7.22, 44.57 +/- 9.80, 40.38 +/- 7.76, and 14.86 +/- 7.23 % injected dose per gram of tissue at 4, 24, 72, 120, and 168 hours after injection, respectively. Immunotherapy with cold panitumumab (four doses of 10 mg/kg) did not cause significant antitumor effect. RIT with a single dose of 100 microCi (90)Y-DOTA-panitumumab caused significant tumor growth delay and improved the survival in UM-SCC-22B tumor model. A single dose of 200 microCi (90)Y-DOTA-panitumumab led to almost complete tumor regression (tumor volumes were 34.83 +/- 11.11 mm(3) and 56.02 +/- 39.95 mm(3) on days 0 and 46 after treatment, respectively). Histopathologic analysis of tumors and normal organs further validated the therapeutic efficacy and limited systemic toxicity of (90)Y-DOTA-panitumumab. The high tumor uptake and prolonged tumor retention, as well as effective therapy, reveal that (90)Y-DOTA-panitumumab may be a promising radioimmunotherapeutic agent to treat EGFR-positive solid tumors.

(c) 2010 AACR.

http://dx.doi.org/10.1158/1535-7163.MCT-10-0444

Molecular imaging provides a powerful tool for early disease detection, characterization, and real-time monitoring of therapeutic responses. Central to molecular imaging is the development of imaging probes. Receptors that are overexpressed in tumors have been potential targets for cancer imaging using targeted molecular probes. Since many cancer types simultaneously overexpress several receptors, the design of dual receptor-targeted molecular imaging probes has recently been proposed. Peptide heterodimers, and microbubble-based dual-targeted probes have shown especially good performance for in vivo cancer imaging. The success of these molecular probes demonstrates that the dual-targeting strategy is generally a good approach for developing molecular probes. In this review, we will introduce the current state of development of dual-targeted molecular imaging probes and summarize the various dual-targeted molecular probes for in vivo cancer imaging.

http://www.benthamdirect.org/pages/b_viewarticle.p

PURPOSE:

This report presents the synthesis of a cyclic RGD dimer conjugate, MAG(2)-G(3)-E[G(3)-c(RGDfK)](2) (MAG(2)-3G(3)-dimer, G(3) = Gly-Gly-Gly, MAG(2) = S-benzoyl mercaptoacetylglycylglycyl), and evaluation of its (99m)Tc complex, (99m)TcO(MAG(2)-3G(3)-dimer), as a new radiotracer for imaging the tumor integrin alpha(v)beta(3) expression.

METHODS:

An in vitro displacement assay was used to determine the integrin alpha(v)beta(3) binding affinity of MAG(2)-3G(3)-dimer against (125)I-c(RGDyK) bound to U87MG human glioma cells. The athymic nude mice bearing U87MG glioma xenografts were used for biodistribution and planar imaging studies.

RESULTS:

We found that (1) MAG(2) is such a highly effective bifunctional chelator that (99m)TcO(MAG(2)-3G(3)-dimer) can be prepared in high yield (radiochemical purity >95%) and with high specific activity ( approximately 5 Ci/micromol) using a kit formulation; (2) (99m)TcO(MAG(2)-3G(3)-dimer) has very high solution stability in the kit matrix; and (3) (99m)TcO(MAG(2)-3G(3)-dimer) has very fast clearance kinetics from the intestine, liver, and kidneys. Among the (99m)Tc-labeled cyclic RGD peptides evaluated in the xenografted U87MG glioma models, (99m)TcO(MAG(2)-3G(3)-dimer) has the best pharmacokinetics and tumor to background ratios (tumor/liver = 4.29 +/- 1.00 at 30 min postinjection and 8.29 +/- 1.50 at 120 min postinjection; tumor/kidney = 1.16 +/- 0.19 at 30 min postinjection and 2.49 +/- 0.25 at 120 min postinjection). Planar imaging studies showed that tumors in the glioma-bearing mice administered with (99m)TcO(MAG(2)-3G(3)-dimer) can be visualized with excellent contrast as early as 15 min postinjection. (99m)TcO(MAG(2)-3G(3)-dimer) was able to maintain its chemical integrity in kidneys (>80% intact) and liver (>95% intact) over the 2-h period. However, there was significant metabolism (>50% of the injected radioactivity) detected in both urine and feces samples.

CONCLUSION:

(99m)TcO(MAG(2)-3G(3)-dimer) is a very attractive radiotracer for early detection of integrin alpha(v)beta(3)-positive tumors and has significant advantages over the (18)F-labeled RGD peptide radiotracers with respect to the cost, availability, and easiness for routine clinical preparation.

Radiolabeled RGD (Arg-Gly-Asp) and bombesin (BBN) radiotracers that specifically target integrin alpha(v)beta(3) and gastrin releasing peptide receptor (GRPR) are both promising radiopharmaceuticals for tumor imaging. We recently designed and synthesized a RGD-BBN heterodimeric peptide with both RGD and BBN motifs in one single molecule. The (18)F-labeled RGD-BBN heterodimer exhibited dual integrin alpha(v)beta(3) and GRPR targeting in a PC-3 prostate cancer model. In this study we investigated whether radiolabeled RGD-BBN tracers can be used to detect breast cancer by using microPET. Cell binding assay demonstrated that the high GRPR expressing breast cancer cells typically express low to moderate level of integrin alpha(v)beta(3), while high integrin alpha(v)beta(3) expressing breast cancer cells have negligible level of GRPR. We labeled RGD-BBN heterodimer with three positron emitting radionuclides (18)F, (64)Cu, and (68)Ga and investigated the corresponding PET radiotracers in both orthotopic T47D (GRPR(+)/low integrin alpha(v)beta(3)) and MDA-MB-435 (GRPR(-)/integrin alpha(v)beta(3)(+)) breast cancer models. The three radiotracers all possessed in vitro dual integrin alpha(v)beta(3) and GRPR binding affinity. The advantages of the RGD-BBN radiotracers over the corresponding BBN analogues are obvious for imaging MDA-MB-435 (GRPR(-)/integrin alpha(v)beta(3)(+)) tumor. (18)F-FB-PEG(3)-RGD-BBN showed lower tumor uptake than (64)Cu-NOTA-RGD-BBN and (68)Ga-NOTA-RGD-BBN but was able to visualize breast cancer tumors with high contrast. Synthesis of (64)Cu-NOTA-RGD-BBN and (68)Ga-NOTA-RGD-BBN is much faster and easier than (18)F-FB-PEG(3)-RGD-BBN. (64)Cu-NOTA-RGD-BBN showed prolonged tumor uptake but also higher liver retention and kidney uptake than (68)Ga-NOTA-RGD-BBN and (18)F-FB-PEG(3)-RGD-BBN. (68)Ga-NOTA-RGD-BBN possessed high tumor signals but also relatively high background uptake compared with the other two radiotracers. In summary, the prosthetic labeling groups, chelators, and isotopes all have a profound effect on the tumor targeting efficacy and in vivo kinetics of the RGD-BBN tracers for dual integrin and GRPR recognition. Further development of suitably labeled RGD-BBN tracers for PET imaging of cancer is warranted.

PURPOSE:

Various radiolabeled Arg-Gly-Asp (RGD) peptides have been previously investigated for tumor integrin alpha(v)beta(3) imaging. To further develop RGD radiotracers with enhanced tumor-targeting efficacy and improved in vivo pharmacokinetics, we designed a new RGD homodimeric peptide with two PEG(4) spacers (PEG(4) = 15-amino-4,7,10,13-tetraoxapentadecanoic acid) between the two monomeric RGD motifs and one PEG(4) linker on the glutamate alpha-amino group ((18)F-labeled PEG(4)-E[PEG(4)-c(RGDfK)](2), P-PRGD2), as a promising agent for noninvasive imaging of integrin expression in mouse models.

METHODS:

P-PRGD2 was labeled with (18)F via 4-nitrophenyl 2-(18)F-fluoropropionate ((18)F-FP) prosthetic group. In vitro and in vivo characteristics of the new dimeric RGD peptide tracer (18)F-FP-P-PRGD2 were investigated and compared with those of (18)F-FP-P-RGD2 ((18)F-labeled RGD dimer without two PEG(4) spacers between the two RGD motifs). The ability of (18)F-FP-P-PRGD2 to image tumor vascular integrin expression was evaluated in a 4T1 murine breast tumor model.

RESULTS:

With the insertion of two PEG(4) spacers between the two RGD motifs, (18)F-FP-P-PRGD2 showed enhanced integrin alpha(v)beta(3)-binding affinity, increased tumor uptake and tumor-to-nontumor background ratios compared with (18)F-FP-P-RGD2 in U87MG tumors. MicroPET imaging with (18)F-FP-P-PRGD2 revealed high tumor contrast and low background in tumor-bearing nude mice. Biodistribution studies confirmed the in vivo integrin alpha(v)beta(3)-binding specificity of (18)F-FP-P-RGD2. (18)F-FP-P-PRGD2 can specifically image integrin alpha(v)beta(3) on the activated endothelial cells of tumor neovasculature.

CONCLUSION:

(18)F-FP-P-PRGD2 can provide important information on integrin expression on the tumor vasculature. The high integrin binding affinity and specificity, excellent pharmacokinetic properties and metabolic stability make the new RGD dimeric tracer (18)F-FP-P-PRGD2 a promising agent for PET imaging of tumor angiogenesis and for monitoring the efficacy of antiangiogenic treatment.

Radiolabeled RGD and bombesin peptides have been extensively investigated for tumor integrin alpha(v)beta(3) and GRPR imaging, respectively. Due to the fact that many tumors are both integrin and GRPR positive, we designed and synthesized a heterodimeric peptide Glu-RGD-BBN, which is expected to be advantageous over the monomeric peptides for dual-receptor targeting. A PEG(3) spacer was attached to the glutamate alpha-amino group of Glu-RGD-BBN to enhance the (18)F labeling yield and to improve the in vivo kinetics. PEG(3)-Glu-RGD-BBN possesses the comparable GRPR and integrin alpha(v)beta(3) receptor-binding affinities as the corresponding monomers, respectively. The dual-receptor targeting properties of (18)F-FB-PEG(3)-Glu-RGD-BBN were observed in PC-3 tumor model. (18)F-FB-PEG(3)-Glu-RGD-BBN with high tumor contrast and favorable pharmacokinetics is a promising PET tracer for dual integrin and GRPR positive tumor imaging. This heterodimer strategy may also be an applicable method to develop other molecules with improved in vitro and in vivo characterizations for tumor diagnosis and therapy.

PURPOSE:

Radiolabeled cyclic RGD (Arg-Gly-Asp) peptides have great potential for the early tumor detection and noninvasive monitoring of tumor metastasis and therapeutic response. (18)F-labeled RGD analogs ([(18)F]-AH111585 and [(18)F]Galacto-RGD) have been investigated in clinical trials for positron emission tomography (PET) imaging of integrin expression in cancer patients. To develop new RGD radiotracers with higher tumor accumulation, improved in vivo kinetics, easy availability and low cost, we developed two new RGD peptides and labeled them with generator-eluted (68)Ga (t(1/2) = 68 min) for PET imaging of integrin alpha(v)beta(3) expression in tumor xenograft models.

MATERIALS AND METHODS:

The two new cyclic RGD dimers, E[PEG(4)-c(RGDfK)](2) (P(4)-RGD2, PEG(4) = 15-amino-4,7,10,13-tetraoxapentadecanoic acid) and E[Gly(3)-c(RGDfK)](2) (G(3)-RGD2, G(3) = Gly-Gly-Gly) were designed, synthesized and conjugated with 1,4,7-triazacyclononanetriacetic acid (NOTA) for (68)Ga labeling. The microPET imaging and biodistribution of the (68)Ga labeled RGD tracers were investigated in integrin alpha(v)beta(3)-positive tumor xenografts.

RESULTS:

The new RGD dimers with the Gly(3) and PEG(4) linkers showed higher integrin alpha(v)beta(3) binding affinity than no-linker RGD dimer (RGD2). NOTA-G(3)-RGD2 and NOTA-P(4)-RGD2 could be labeled with (68)Ga within 30 min with higher purity (>98%) and specific activity (8.88-11.84 MBq/nmol). Both (68)Ga-NOTA-P(4)-RGD2 and (68)Ga-NOTA-G(3)-RGD2 exhibited significantly higher tumor uptake and tumor-to-normal tissue ratios than (68)Ga-NOTA-RGD2.

CONCLUSION:

Because of their high affinity, high specificity and excellent pharmacokinetic properties, further investigation of the two novel RGD dimers for clinical PET imaging of integrin alpha(v)beta(3) expression in cancer patients is warranted.

http://dx.doi.org/10.1007/s00259-008-1045-1

A novel dual-modality molecular probe composed of biocompatible Fe(3)O(4) nanocrystal, monoclonal antibody and radionuclide was designed and prepared. All functional components in the dual-modality molecular probe, i.e., Fe(3)O(4), PEG, mAb 3H11 and (125)I, were chemically bonded together for forming a stable molecular probe. Systematic in vitro experiments were carried out for evaluating the biological activity of the antibody in the targeting probe. A series of in vivo experiments were performed based on the dual-modality imaging probe for detecting xenografted tumors in nude mice by MRI and gamma-imaging techniques. The pharmacokinetics of the dual-modality molecular probe in tumor-bearing nude mice was studied.

PURPOSE:

Internalization is one of the key steps for anticancer immunoconjugates to deliver the drugs inside of cancer cells. Herein, the internalization property of antiepidermal growth factor receptor (EGFR) monoclonal antibody (mAb) LA22 was evaluated.

MATERIALS AND METHODS:

The binding and internalization properties of LA22 on A549 cells were investigated by using 125I-LA22. In vitro internalization was also confirmed by indirect fluorescent staining. In vivo tumor targeting and internalization of 125I-LA22 were evaluated in the A549 nude mice model.

RESULTS:

The mAb LA22 showed a high affinity to EGFRs expressed on A549 cells (Kd = 0.69 +/- 0.13 nM). The in vitro internalization of LA22 was time- and temperature dependent. The cell-surface-bound LA22 was rapidly internalized at 37 degrees C. The experimental results of LA22 internalization obtained from radioassay and fluorescent staining were consistent with a good linear correlation. At 72 hours postinjection, a clear gamma-image of tumor was obtain in A549 tumor xenografts, and the tumor uptake of 125I-LA22 was 8.00 +/- 0.61 percent injected dose per gram (%ID/g) (2.19 +/- 0.37 %ID/g for 125I-mIgG). Similar to the in vitro observation, 64.06% of the cell-bound mAb LA22 was internalized into the tumor cells in vivo.

CONCLUSIONS:

The mAb, LA22, is a rapid, high-internalizing antibody, and this property makes it a promising vehicle for tumor-targeted drug delivery.

Anti-angiogenesis is a promising strategy for the treatment of cancer. Integrins, consisting of two noncovalently bound transmembrane alpha and beta subunits, are an important molecular family involved in tumor angiogenesis. The blockade of integrin signaling has been demonstrated to be efficient to inhibit tumor growth, angiogenesis, and metastasis. Among all the integrins, alpha(v)beta(3) seems to be the most important one during tumor angiogenesis. The inhibition of integrin alpha(v)beta(3) signaling with antibodies, peptides, peptidomimetics, and other antagonists has great potential in the treatment of cancer. In addition, integrin alpha(v)beta(3) is highly expressed on activated endothelial cells, new-born vessels as well as some tumor cells, but is not present in resting endothelial cells and most normal organ systems, making it a suitable target for anti-angiogenic therapy. In this article we will review the role of integrin alpha(v)beta(3) in angiogenesis, present recent progress in the use of integrin alpha(v)beta(3) antagonists and integrin-targeted delivery systems as potential cancer therapeutics, and discuss future perspectives.

http://dx.doi.org/10.1002/ddr.20265

Abstract

In this report, we present in vitro and in vivo evaluation of three 111 In-labeled DTPA conjugates of a cyclic RGDfK dimer: DTPA-Bn-SU016 (SU016 = E[c(RGDfK)] 2; DTPA-Bn = 2-( p-isothioureidobenzyl)diethylenetriaminepentaacetic acid), DTPA-Bn-E-SU016 ( E = glutamic acid) and DTPA-Bn-Cys-SU016 (Cys = cysteic acid). The integrin alpha vbeta 3 binding affinities of SU016, DTPA-Bn-SU016, DTPA-Bn-E-SU016, and DTPA-Bn-Cys-SU016 were determined to be 5.0 +/- 0.7 nM, 7.9 +/- 0.6 nM, 5.8 +/- 0.6 nM, and 6.9 +/- 0.9 nM, respectively, against 125 I-c(RGDyK) in binding to integrin alpha vbeta3, suggesting that E or Cys residue has little effect on the integrin alpha vbeta3 affinity of E[c(RGDfK)] 2. It was also found that the 111 In-labeling efficiency of DTPA-Bn-SU016 and DTPA-Bn-E-SU016 is 3-5 times better than that of DOTA analogues due to fast chelation kinetics and high-yield 111 In-labeling under mild conditions (e.g., room temperature). Biodistribution studies were performed using BALB/c nude mice bearing U87MG human glioma xenografts. 111 In-DTPA-Bn-SU016, 111 In-DTPA-Bn-E-SU016, and 111 In-DTPA-Bn-Cys-SU016 all displayed rapid blood clearance. Their tumor uptake was comparable between 0.5 and 4 h postinjection (p.i.) within experimental error. 111 In-DTPA-Bn-E-SU016 had a significantly lower ( p < 0.01) kidney uptake than 111 In-DTPA-Bn-SU016 and 111 In-DTPA-Bn-Cys-SU016. The liver uptake of 111 In-DTPA-Bn-SU016 was 1.69 +/- 0.18% ID/g at 24 h p.i., while the liver uptake values of 111 In-DTPA-Bn-E-SU016 and 111 In-DTPA-Bn-Cys-SU016 were 0.55 +/- 0.11% ID/g and 0.79 +/- 0.15% ID/g at 24 h p.i., respectively. Among the three 111 In radiotracers evaluated in this study, 111 In-DTPA-Bn-E-SU016 has the lowest liver and kidney uptake and the best tumor/liver and tumor/kidney ratios. Results from metabolism studies indicated that there is little metabolism (<10%) for three 111 In radiotracers at 1 h p.i. Imaging data showed that tumors can be clearly visualized at 4 h p.i. with good contrast in the tumor-bearing mice administered with 111 In-DTPA-Bn-E-SU016. It is concluded that using a glutamic acid linker can significantly improve excretion kinetics of the 111 In-labeled E[c(RGDfK)] 2 from liver and kidneys.

http://dx.doi.org/10.1021/bc7002988

Anti-EGFR monoclonal antibodies LA22 and Erbitux bind to different epitopes of EGFR. The chemimmunoconjugates of MMC with LA22 or Erbitux were prepared, and in vitro cytotoxicity assays with A549 cells showed that LA22-MMC was much more potent than Erbitux or Erbitux-MMC. Viabilities of A549 cells treated with LA22-MMC, Erbitux or Erbitux-MMC were 35%, 94%, and 81%, respectively. Immunoscintigraphy of xenografts of human A431 and A549 cells in nude mice both showed that (125)I-labeled-LA22-MMC enriched in tumor sites prominently. Most importantly, in vivo assays showed LA22-MMC was significantly more effective than free drug MMC in the treatment of subcutaneous xenografts of human A431 cells innude mice (83% inhibition for LA22-MMC and 30% for MMC). We concluded that LA22-MMC could be a very potent drug for treatment of solid tumors.http://dx.doi.org/10.1016/j.bbrc.2006.08.114

Abstract

The possibility of monitoring stem cells in vivo with radionuclide imaging after transplantation was investigated. Based on the results of a radioligand receptors assay that human mesenchymal stem cells (hMSCs) express a high level of transferrin receptors, iodinated transferrin (131I-Tf(Fe)2) was chosen as the radiotracer for imaging the cells implanted into the spinal cords of rabbits. Accumulation of radioactivity at the cell transplanted sites was assessed 16 and 24 hours post-intrathecal injection of 131I-Tf(Fe)2. Transferrin receptors expression and Tf binding of the implanted cells were verified by immunofluorescence and ex vivo phosphor imaging. The specificity of Tf uptake of hMSCs was proved through control experiments, i.e., replacing 131I-Tf(Fe)2 with 131I labeled human serum albumin as the tracer or substituting hMSCs with phosphate buffered saline as the grafts. Despite some defects, such as the invasive administration of the tracer and the non-specificity of transferrin receptors as a marker of stem cells in this preliminary study, the technique of nuclear medicine imaging is considered to have great potential in tracking implanted cells in vivo.

http://dx.doi.org/10.1016/j.nucmedbio.2004.04.001