Multimodal Imaging of Integrin Receptor-Positive Tumors by Bioluminescence, Fluorescence, Gamma Scintigraphy, and Single-Photon Emission Computed Tomography Using a Cyclic RGD Peptide Labeled with a Near-Infrared Fluorescent Dye and a Radionuclide

Abstract

Integrins, particularly the alpha(v)beta(3) heterodimers, play important roles in tumor-induced angiogenesis and invasiveness. To image the expression pattern of the alpha(v)beta(3) integrin in tumors through a multimodality imaging paradigm, we prepared a cyclic RGDyK peptide analogue (LS308) bearing a tetraazamacrocycle 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA) and a lipophilic near-infrared (NIR) fluorescent dye cypate. The alpha(v)beta(3) integrin binding affinity and the internalization properties of LS308 mediated by the alpha(v)beta(3) integrin in 4t1luc cells were investigated by receptor binding assay and fluorescence microscopy, respectively. The in vivo distribution of (111)In-labeled LS308 in a 4t1luc tumor-bearing mouse model was studied by fluorescence, bioluminescence, planar gamma, and single-photon emission computed tomography (SPECT). The results show that LS308 has high affinity for alpha(v)beta(3) integrin and internalized preferentially via the alpha(v)beta(3) integrin-mediated endocytosis in 4t1luc cells. We also found that LS308 selectively accumulated in alpha(v)beta(3)-positve tumors in a receptor-specific manner and was visualized by the four imaging methods. Whereas the endogenous bioluminescence imaging identified the ensemble of the tumor tissue, the fluorescence and SPECT methods with the exogenous contrast agent LS308 reported the local expression of alpha(v)beta(3) integrin. Thus, the multimodal imaging approach could provide important complementary diagnostic information for monitoring the efficacy of new antiangiogenic drugs.

Validation study of 131I-RRL: Assessment of biodistribution, SPECT imaging and radiation dosimetry in mice

“…An increasing number of studies are focusing on radiolabeled molecular probes, which target newly formed tumor vessels (12)(13)(14)(15)(16).…”

Bioluminescence imaging: progress and applications

“…Transgenic mice based on VEGF receptor 2 (VEGFR2) promoter driving the expression of Fluc reporter can be used to monitor angiogenesis induced by tumors, skin wounding and contact hypersensitivity [72]. Further, many other luciferase-based reporters for angiogenesis imaging have been recently described [73, 74]. …”

Multimodal Interventional Molecular Imaging of Tumor Margins and Distant Metastases by Targeting αvβ3 Integrin

“…Such a probe could also be applied in ex vivo pathological evaluation of excised specimens to identify tumor tissue and validate tumor free excision margins. Although, a number of such multimodal RGD-derivatives have already been reported in literature, [26-30] to the best of our knowledge so far none has been studied for their potential in surgical guidance and combined pre- and intraoperative imaging.…”