Bing Jia

99mTc-3PRGD2 for Integrin Receptor Imaging of Lung Cancer: A Multicenter Study

99mTc-3PRGD2 is a new SPECT tracer targeting integrin αVβ3 receptor for detecting tumors, imaging angiogenesis, and evaluating tumor response to therapy. A multicenter study was designed to investigate the efficacy of 99mTc-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 99mTc-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 99mTc-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: 99mTc-3PRGD2 imaging at 1 h is sensitive for the detection of lung cancer, meriting further investigation of 99mTc-3PRGD2 as a novel clinical tracer for integrin receptor imaging.

A Novel Type of Dual-Modality Molecular Probe for MR and Nuclear Imaging of Tumor: Preparation, Characterization and in Vivo Application

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.

Integrin αvβ3-Targeted Radioimmunotherapy of Glioblastoma Multiforme

Purpose: Abegrin is a monoclonal antibody to human integrin αVβ3, a cell adhesion molecule highly expressed on actively angiogenic endothelium and glioblastoma multiforme tumor cells. The purpose of this study was to evaluate the efficacy of a novel 90Y-Abegrin radioimmunotherapeutic agent in murine xenograft glioblastoma models with noninvasive in vivo molecular imaging modalities. Experimental Design: A s.c. U87MG human glioblastoma xenograft model was used to determine maximum tolerated dose (MTD), biodistribution, dose response, and efficacy of 90Y-Abegrin. Antitumor efficacy was also characterized in an orthotopic U87MG and in a HT-29 colorectal cancer model, a low integrin-expressing carcinoma. Small-animal positron emission tomography imaging was used to correlate histologic findings of treatment efficacy. Results: MTD and dose response analysis revealed 200 μCi per mouse as appropriate treatment dose with hepatic clearance and no organ toxicity. 90Y-Abegrin–treated U87MG tumor mice showed partial regression of tumor volume, with increased tumor volumes in 90Y-IgG, Abegrin, and saline groups. 18F-FDG imaging revealed a reduction of cell proliferation and metabolic activity whereas 18F-FLT reflected decreased DNA synthesis in the 90Y-Abegrin group. Ki67 analysis showed reduced proliferative index and quantitative terminal deoxynucleotidyl transferase dUTP nick-end labeling–positive analysis revealed increased DNA fragmentation and apoptosis in 90Y-Abegrin animals. CD31 and 4′,6-diamidino-2-phenylindole staining showed increased vascular fragmentation and dysmorphic vessel structure in 90Y-Abegrin animals only. Orthotopic U87MG tumors treated with 90Y-Abegrin displayed reduced tumor volume. HT-29 tumors showed no significant difference among the various groups. Conclusion: Radioimmunotherapy with 90Y-labeled Abegrin may prove promising in the treatment of highly vascular, invasive, and heterogeneous malignant brain tumors.

Evaluation of 111In-Labeled Cyclic RGD Peptides: Tetrameric Not Tetravalent

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.

Two (90)Y-Labeled Multimeric RGD Peptides RGD4 and 3PRGD2 for Integrin Targeted Radionuclide Therapy

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.

Epidermal Growth Factor Receptor–Targeted Radioimmunotherapy of Human Head and Neck Cancer Xenografts Using 90Y-Labeled Fully Human Antibody Panitumumab

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 β− emitter 90Y-labeled panitumumab. Biodistribution and planar γ-imaging studies were carried out with 111In-DOTA-panitumumab. The RIT efficacy of 90Y-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 111In-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 μCi 90Y-DOTA-panitumumab caused significant tumor growth delay and improved the survival in UM-SCC-22B tumor model. A single dose of 200 μCi 90Y-DOTA-panitumumab led to almost complete tumor regression (tumor volumes were 34.83 ± 11.11 mm3 and 56.02 ± 39.95 mm3 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 90Y-DOTA-panitumumab. The high tumor uptake and prolonged tumor retention, as well as effective therapy, reveal that 90Y-DOTA-panitumumab may be a promising radioimmunotherapeutic agent to treat EGFR-positive solid tumors. Mol Cancer Ther; 9(8); 2297–308. ©2010 AACR.

Molecular imaging of tumor-infiltrating macrophages in a preclinical mouse model of breast cancer.

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.

Integrin αvβ6–Targeted SPECT Imaging for Pancreatic Cancer Detection

Integrin αvβ6, a member of the integrin family, is specifically expressed in many malignancies but not in normal organs. Overexpression of integrin αvβ6 is usually correlated with malignant potential and poor prognosis. In this study, we describe the synthesis and evaluation of a 99mTc-labeled integrin αvβ6–targeting peptide as a SPECT radiotracer for the in vivo imaging of integrin αvβ6 expression. Methods: An integrin αvβ6–targeting peptide (denoted as the HK peptide) was conjugated with 6-hydrazinonicotinyl (HYNIC) and radiolabeled with 99mTc using tricine and TPPTS (trisodium triphenylphosphine-3,3′,3″-trisulfonate) as coligands. The in vitro and in vivo characteristics of 99mTc-HYNIC(tricine)(TPPTS)-HK (99mTc-HHK) were investigated in BxPC-3 (integrin αvβ6–positive) and HEK293 (integrin αvβ6–negative) models. The ability of 99mTc-HHK to detect liver metastasis of pancreatic cancer was evaluated using small-animal SPECT/CT. Results: 99mTc-HHK showed high integrin αvβ6–binding specificity both in vitro and in vivo. 99mTc-HHK was cleared rapidly from the blood and normal organs except for the kidneys. The highest uptake (0.88 ± 0.12 percentage injected dose per gram) of 99mTc-HHK in BxPC-3 tumors was observed at 0.5 h after injection. High-contrast images of integrin αvβ6–positive tumors were obtained using 99mTc-HHK. The minimum nonspecific activity accumulation in normal liver tissues rendered high-quality SPECT/CT images of metastatic lesions. Conclusion: 99mTc-HHK is a promising SPECT radiotracer for the noninvasive imaging of integrin αvβ6 expression in vivo. SPECT/CT with 99mTc-HHK could provide an effective approach for the noninvasive detection of primary and metastatic lesions of integrin αvβ6–positive tumors.

Polymer–Doxorubicin Conjugate Micelles Based on Poly(ethylene glycol) and Poly(N-(2-hydroxypropyl) methacrylamide): Effect of Negative Charge and Molecular Weight on Biodistribution and Blood Clearance

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.

PET imaging of neovascularization with (68)Ga-3PRGD2 for assessing tumor early response to Endostar antiangiogenic therapy.

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.