Imaging Of Integrin Αvβ3 Expression Research Articles

Comparison of integrin αvβ3 expression with 68Ga-NODAGA-RGD PET/CT and glucose metabolism with 18F-FDG PET/CT in esophageal or gastroesophageal junction cancers

BackgroundThe primary aims of this study were to compare in patients with esophageal or esophagogastric junction cancers the potential of 68Ga-NODAGA-RGD PET/CT with that of 18F-FDG PET/CT regarding tumoral uptake and distribution, as well as histopathologic examination.MethodsTen 68Ga-NODAGA-RGD and ten 18F-FDG PET/CT were performed in nine prospectively included participants (1 woman; aged 58 ± 8.4 y, range 40–69 y). Maximum SUV (SUVmax) and metabolic tumor volumes (MTV) were calculated. The Mann–Whitney U test and Spearman correlation analysis (ρ) were used.Results68Ga-NODAGA-RGD PET/CT detected positive uptake in 10 primary sites (8 for primary tumors and 2 for local relapse suspicion), 6 lymph nodes and 3 skeletal sites. 18F-FDG PET/CT detected positive uptake in the same sites but also in 16 additional lymph nodes and 1 adrenal gland. On a lesion-based analysis, SUVmax of 18F-FDG was significantly higher than those of 68Ga-NODAGA-RGD (4.9 [3.7–11.3] vs. 3.2 [2.6–4.2] g/mL, p = 0.014). Only one participant showed a higher SUVmax in an osseous metastasis with 68Ga-NODAGA-RGD as compared to 18F-FDG (6.6 vs. 3.9 g/mL). Correlation analysis showed positive correlation between 18F-FDG and 68Ga-NODAGA-RGD PET parameters (ρ = 0.56, p = 0.012 for SUVmax, ρ = 0.78, p < 0.001 for lesion-to-background ratios and ρ = 0.58, p = 0.024 for MTV). We observed that 18F-FDG uptake was homogenous inside all the confirmed primary sites (n = 9). In contrast, 68Ga-NODAGA-RGD PET showed more heterogenous uptake in 6 out of the 9 confirmed primary sites (67%), seen mostly in the periphery of the tumor in 5 out of the 9 confirmed primary sites (56%), and showed slight extensions into perilesional structures in 5 out of the 9 confirmed primary sites (56%).ConclusionsIn conclusion, 68Ga-NODAGA-RGD has lower potential in the detection of esophageal or esophagogastric junction malignancies compared to 18F-FDG. However, the results suggest that PET imaging of integrin αvβ3 expression may provide complementary information and could aid in tumor diversity and delineation.Trial registration: Trial registration: NCT02666547. Registered January 28, 2016—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT02666547.

Hybrid PET/optical imaging of integrin αVβ3 receptor expression using a (64)Cu-labeled streptavidin/biotin-based dimeric RGD peptide.

BackgroundHybrid PET/optical imaging provides quantitative and complementary information for diagnosis of tumors. Herein, we developed a 64Cu-labeled AlexaFluor 680-streptavidin ((AF)SAv)/biotin-based dimeric cyclic RGD peptide (RGD2) for hybrid PET/optical imaging of integrin αVβ3 expression.Methods64Cu-1,4,7,10-tetraazacyclododecane-N,N′,N′′,N′′′-tetraacetic acid (DOTA)-(AF)SAv/biotin-PEG-RGD2 was prepared by formation of a complex comprising DOTA-(AF)SAv and biotin-PEG-RGD2, followed by radiolabeling with 64Cu. Receptor binding studies of DOTA-(AF)SAv/biotin-PEG-RGD2 were performed using U87MG cells and 125I-RGDyK as the radioligand, and cellular uptake studies of 64Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 were also performed. MicroPET imaging followed by optical imaging of U87MG tumor-bearing mice was acquired after injection of the hybrid probe, and region of interest (ROI) analysis of tumors was performed. Ex vivo PET/optical imaging and biodistribution studies of the major tissues were performed after the in vivo imaging, and immunofluorescence staining of the tumor tissue sections was carried out.Results64Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 was prepared in 52.1 ± 5.4 % radiochemical yield and with specific activity of 1.0 ± 0.1 GBq/mg. Receptor binding studies showed that DOTA-(AF)SAv/biotin-PEG-RGD2 had higher binding affinity for integrin αVβ3 than RGD2, reflecting a possible polyvalency effect. Moreover, the hybrid probe revealed time-dependent uptake by U87MG cells. In a microPET/optical imaging study, the hybrid probe demonstrated high accumulation in tumors; ROI analysis revealed 2.7 ± 0.2 % ID/g at 1 h and 4.7 ± 0.2 % ID/g at 21 h after injection, and subsequently acquired optical images showed tumors with strong fluorescence intensity. Ex vivo PET/optical images of the major tissues confirmed the in vivo imaging data, and biodistribution studies demonstrated high and specific uptake in tumors (4.8 ± 0.1 % ID/g). Immunofluorescence staining showed the formation of new blood vessels in tumor tissues, suggesting that the tumor uptake was due to specific binding of the hybrid probe to integrin αVβ3 expressed on tumor cells.ConclusionsThese results indicate that a 64Cu-DOTA-(AF)SAv/biotin-PEG-RGD2 is able to provide quantitative information on hybrid PET/optical imaging of integrin αVβ3 expression.

Can 111In-RGD2 monitor response to therapy in head and neck tumor xenografts?

RGD (arginylglycylaspartic acid)-based imaging tracers allow specific imaging of integrin αvβ3 expression, proteins overexpressed during angiogenesis; however, few studies have investigated the potential of these tracers to monitor responses of antiangiogenic or radiation therapy. In the studies presented here, (111)In-RGD2 was assessed for its potential as an imaging tool to monitor such responses to therapies. DOTA-E-[c(RGDfK)]2 was radiolabeled with (111)In ((111)In-RGD2), and biodistribution studies were performed in mice with subcutaneous FaDu or SK-RC-52 xenografts after treatment with either antiangiogenic therapy (bevacizumab or sorafenib) or tumor irradiation (10 Gy). Micro-SPECT imaging studies and subsequent quantitative analysis were also performed. The effect of bevacizumab, sorafenib, or radiation therapy on tumor growth was determined. The uptake of (111)In-RGD2 in tumors, as determined from biodistribution studies, correlated well with that quantified from micro-SPECT images, and both showed that 15 d after irradiation (111)In-RGD2 uptake was enhanced. Specific or nonspecific uptake of (111)In-RGD2 in FaDu or SK-RC-52 xenografts was not affected after antiangiogenic therapy, except in head and neck squamous cell carcinoma 19 d after the start of sorafenib therapy (P < 0.05). The uptake of (111)In-RGD2 followed tumor volume in studies featuring antiangiogenic therapy. However, the uptake of (111)In-RGD2 in FaDu xenografts was decreased as early as 4 h after tumor irradiation, despite nonspecific uptake remaining unaltered. Tumor growth was inhibited after antiangiogenic or radiation therapy. Here, it is suggested that (111)In-RGD2 could allow in vivo monitoring of angiogenic responses after radiotherapy and may therefore prove a good clinical tool to monitor angiogenic responses early after the start of radiotherapy in patients with head and neck squamous cell carcinoma. Despite clear antitumor efficacy, antiangiogenic therapy did not alter tumor uptake of (111)In-RGD2, indicating that integrin expression was not altered.

(44)Sc: an attractive isotope for peptide-based PET imaging.

The overexpression of integrin αvβ3 has been linked to tumor aggressiveness and metastasis in several cancer types. Because of its high affinity, peptides containing the arginine–glycine–aspartic acid (RGD) motif have been proven valuable vectors for noninvasive imaging of integrin αvβ3 expression and for targeted radionuclide therapy. In this study, we aim to develop a 44Sc-labeled RGD-based peptide for in vivo positron emission tomography (PET) imaging of integrin αvβ3 expression in a preclinical cancer model. High quality 44Sc (t1/2, 3.97 h; β+ branching ratio, 94.3%) was produced inexpensively in a cyclotron, via proton irradiation of natural Ca metal targets, and separated by extraction chromatography. A dimeric cyclic-RGD peptide, (cRGD)2, was conjugated to 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and radiolabeled with 44Sc in high yield (>90%) and specific activity (7.4 MBq/nmol). Serial PET imaging of mice bearing U87MG tumor xenografts showed elevated 44Sc-DOTA-(cRGD)2 uptake in the tumor tissue of 3.93 ± 1.19, 3.07 ± 1.17, and 3.00 ± 1.25 %ID/g at 0.5, 2, and 4 h postinjection, respectively (n = 3), which were validated by ex vivo biodistribution experiments. The integrin αvβ3 specificity of the tracer was corroborated, both in vitro and in vivo, by competitive cell binding and receptor blocking assays. These results parallel previously reported studies showing similar tumor targeting and pharmacokinetic profiles for dimeric cRGD peptides labeled with 64Cu or 68Ga. Our findings, together with the advantageous radionuclidic properties of 44Sc, capitalize on the relevance of this isotope as an attractive alternative isotope to more established radiometals for small molecule-based PET imaging, and as imaging surrogate of 47Sc in theranostic applications.

Development of RGD-Based Radiotracers for Tumor Imaging and Therapy: Translating from Bench to Bedside

The cell adhesion molecule integrin αvβ3 is an important player in the process of angiogenesis. In the last decades, a series of radiolabeled Arg-Gly-Asp (RGD) peptides targeting integrin αvβ3 has been prepared and optimized for positron emission tomography (PET) and single-photon-emission computed tomography (SPECT) imaging of integrin αvβ3 expression. Several promising radiotracers have been tested in clinical trials. In this review, we will introduce strategies that have been used to optimize and accelerate RGD radiotracers towards clinical translation; illustrate RGD-based radiotracers that have been investigated in clinical trials; and discuss the other applications of RGD radiotracers aside from tumor detection.

Imaging of Integrin α v β 3 Expression Using 68 Ga-RGD Positron Emission Tomography in Pediatric Cerebral Infarct

Enhanced expression of integrin αvβ3 is commonly used as a biomarker for angiogenesis, which is one of the key pathophysiologic processes in cerebral infarct. Integrin αvβ3 can be imaged with arginine-glycine-aspartic acid (RGD) peptide agents. In this study, characteristics of positron emission tomography (PET) using a 68Ga-labeled RGD were investigated in pediatric cerebral infarct. Pediatric patients with moyamoya disease underwent 68Ga-RGD PET in a research protocol for neovascularization evaluation. In these patients, 17 cerebral infarct lesions of 10 patients were included in the analysis. On 68Ga-RGD PET, the infarct lesion to contralateral brain ratio (LCR) of the infarct lesion was measured and analyzed with regard to postinfarct time interval (PTI) and perfusion single-photon emission computed tomography (SPECT) findings. An increase in 68Ga-RGD uptake was observed in cerebral infarct, particularly in recent lesions. The LCR was significantly higher in the recent than in the chronic lesions, and a significant correlation existed between the LCR and PTI. Additionally, the LCR was significantly higher in the lesions with hyperperfusion on SPECT. This study, as the first human study using an RGD agent for in vivo cerebral infarct imaging, demonstrated that 68Ga-RGD PET has a potential for molecular imaging of integrin αvβ3 expression in cerebral infarct as a biomarker of angiogenesis.

PET Imaging of Integrin αVβ3 Expression

PET imaging of integrin αvβ3 expression has been studied intensely by the academia and recently also by the industry. Imaging of integrin αvβ3 expression is of great potential value, as the integrin αvβ3 is a key player in tumor metastasis and angiogenesis. Therefore PET imaging of this target might be a suitable in-vivo biomarker of angiogenesis and metastatic potential of tumors. In this manuscript, the various strategies for PET imaging of the integrin αvβ3 will be summarized, including monomeric and multimeric radiolabelled RGD peptides and nanoparticles. While most experiments have been performed using preclinical tumor models, more and more clinical results on PET imaging of αvβ3 expression are available and will be discussed in detail. However, while a multitude of radiotracer strategies have been successfully evaluated for PET imaging of αvβ3, the ultimate clinical value of this new imaging biomarker still has to be evaluated in large clinical trials.

64Cu Labeled AmBaSar-RGD2 for micro-PET Imaging of Integrin αvβ3 Expression

Integrin αvβ3 plays a critical role in tumor-induced angiogenesis and metastasis. Previously, a 64Cu-AmBaSar- RGD monomer with high in vivo stability compared with 64Cu-DOTA-RGD was developed for integrin αvβ3 PET imaging. It has been established that dimeric RGD peptides have higher receptor-binding affinity and superior in vivo kinetics compared with monomeric RGD peptides due to the polyvalency effect. In this context, we synthesized and evaluated 64Cu-labeled AmBaSar dimeric RGD conjugates (64Cu-AmBaSar-RGD2) for PET imaging of integrin αvβ3 expression. The dimeric RGD peptide was conjugated with a cage-like chelator AmBaSar and labeled with 64Cu. Cell binding, microPET imaging, receptor blocking, and biodistribution studies of 64Cu-AmBaSar-RGD2 were conducted in the U87MG human glioblastoma xenograft model. AmBaSar-RGD2 conjugate was obtained in reasonable yield (45.0 ± 2.5%, n= 4) and the identity was confirmed by HPLC and MS (found 1779.8, calculated m/z for [M+H]+ M: C81H125N27O19 1779.9). 64Cu-AmBaSar-RGD2 was obtained with high radiochemical yield (92.0 ± 1.3%) and purity (≥ 98.0%) under mild conditions (pH 5.0~5.5, 23~37 °C) in 30 min. The specific activity of 64Cu-AmBaSar-RGD2 was estimated to be 15-22 GBq/µmol at the end of synthesis. Based on microPET imaging and biodistribution studies, 64Cu-AmBaSar-RGD2 has demonstrated higher tumor uptake at selected time points than 64Cu-AmBaSar-RGD. At 20 h p.i., the tumor uptake reached 0.65 ± 0.05 %ID/g for 64Cu-AmBaSar-RGD and 1.76 ± 0.38 %ID/g for 64Cu-AmBaSar-RGD2, respectively. The integrin αvβ3 targeting specificity was confirmed by blocking experiments. Therefore, the new tracer 64Cu-AmBaSar- RGD2 exhibited better tumor-targeting efficacy and more favorable in vivo pharmacokinetics than the 64Cu labeled RGD monomer due to the polyvalency effect.

Imaging of integrin αvβ3 expression in patients with malignant glioma by [18F] Galacto-RGD positron emission tomography

Inhibitors targeting the integrin alpha(v)beta(3) are promising new agents currently tested in clinical trials for supplemental therapy of glioblastoma multiforme (GBM). The aim of our study was to evaluate (18)F-labeled glycosylated Arg-Gly-Asp peptide ([(18)F]Galacto-RGD) PET for noninvasive imaging of alpha(v)beta(3) expression in patients with GBM, suggesting eligibility for this kind of additional treatment. Patients with suspected or recurrent GBM were examined with [(18)F]Galacto-RGD PET. Standardized uptake values (SUVs) of tumor hotspots, galea, and blood pool were derived by region-of-interest analysis. [(18)F]Galacto-RGD PET images were fused with cranial MR images for image-guided surgery. Tumor samples taken from areas with intense tracer accumulation in the [(18)F]Galacto-RGD PET images and were analyzed histologically and immunohistochemically for alpha(v)beta(3) integrin expression. While normal brain tissue did not show significant tracer accumulation (mean SUV, 0.09 +/- 0.04), GBMs demonstrated significant but heterogeneous tracer uptake, with a maximum in the highly proliferating and infiltrating areas of tumors (mean SUV, 1.6 +/- 0.5). Immunohistochemical staining was prominent in tumor microvessels as well as glial tumor cells. In areas of highly proliferating glial tumor cells, tracer uptake (SUVs) in the [(18)F]Galacto-RGD PET images correlated with immunohistochemical alpha(v)beta(3) integrin expression of corresponding tumor samples. These data suggest that [(18)F] Galacto-RGD PET successfully identifies alpha(v)beta(3) expression in patients with GBM and might be a promising tool for planning and monitoring individualized cancer therapies targeting this integrin.