Specific Targeting of Human Integrin αvβ3 with 111In-Labeled Abegrin™ in Nude Mouse Models

Abstract

Purpose The cell adhesion molecule integrin αvβ3 is an important player in the process of tumor angiogenesis and metastasis. Abegrin™, a fully humanized anti-integrin αvβ3 monoclonal antibody, was currently in clinical trials for cancer therapy. Herein, we labeled Abegrin™ with 111In, evaluated the in vitro and in vivo characteristics, and investigated whether the expression of integrin αvβ3 in tumors could be imaged with 111In-labeled Abegrin™. Methods The binding affinity and specificity of Abegrin™ was analyzed using U87MG glioblastoma cells. Abegrin™ was coupled with 1,4,7,10-tetraazadodecane-N,N,N’,N”-tetraacetic acid (DOTA) for 111In radiolabeling. γ Imaging of 111In-DOTA–Abegrin™ was carried out in nude mice bearing both integrin αvβ3-positive U87MG and integrin αvβ3-negative HT-29 tumors. Biodistribution and blocking studies of 111In-DOTA–Abegrin™ were investigated in U87MG tumor-bearing nude mice. Results Abegrin™ exhibited high-binding affinity to human integrin αvβ3 expressed on U87MG cells (Kd of 0.35±0.06 nM). The antibody retained antigen-binding affinity/specificity after DOTA conjugation. γ Imaging showed that the tumor uptake of 111In-DOTA–Abegrin™ in integrin αvβ3-positive U87MG tumors was much higher than that in integrin αvβ3-negative HT-29 tumors. In the HT-29 tumors, Abegrin™ was mainly nonspecifically accumulated around the blood vessels, while in the U87MG tumors, besides the nonspecific tumor retention, Abegrin™ also specifically bound the human integrin αvβ3 expressed on the tumor cells. Biodistribution and blocking studies exhibited that the U87MG tumor uptake of 111In-DOTA–Abegrin™ decreased from 14.12±0.44 to 6.93±0.94 percentage of injected dose per gram of tissue after coinjection of excess dose of cold Abegrin™, which confirmed the in vivo integrin αvβ3 binding specificity of 111In-DOTA–Abegrin™. Conclusions Abegrin™ showed specific binding to human integrin αvβ3 expressed on the tumor cells. 111In-DOTA–Abegrin™ can specifically target the human integrin αvβ3 expression in the nude mouse model. 111In-DOTA–Abegrin™ has a potential for clinical translation as an agent for integrin αvβ3-positive tumor imaging, evaluating tumor angiogenic status and monitoring the therapeutic efficacy of Abegrin™-based cancer therapy.

v Integrins in Angiogenesis and Cancer

“…Although no objective response was observed in a Phase II trial for melanoma (Hersey et al 2010), Abegrin is currently undergoing testing in eight clinical trials for solid tumors, psoriasis, and rheumatoid arthritis. In addition, Abegrin has shown promise in preclinical models as a targeting ligand for molecular imaging agents (Liu et al 2010). av antibody: This fully human monoclonal antibody that inhibits av has antiangiogenic and antitumor effects in preclinical models (Trikha et al 2004;Chen et al 2008) and was well tolerated in Phase I trials (Mullamitha et al 2007).…”

Signaling mechanism of cell adhesion molecules in breast cancer metastasis: potential therapeutic targets

“…Several examples are presented in Table 2. Etaracizumab (Abegrin, Vitaxin, or MEDI-522), a fully humanized anti-avb3 monoclonal antibody, has not shown significant clinical benefits in phase II clinical trials [100][101][102][103]. Volociximab (M200, Eos 200-4) is a chimeric IgG4 monoclonal antibody (mAb) that specifically targets integrin a5b1 and has been used in the treatment of solid tumors.…”

Early Assessment of Tumor Response to Gefitinib Treatment by Noninvasive Optical Imaging of Tumor Vascular Endothelial Growth Factor Expression in Animal Models

“…Fluorescein isothiocyanate (FITC)-bevacizumab was synthesized by conjugating the VEGF-specific antibody bevacizumab with FITC-NHS (Pierce) using a previously described method (15). Detailed procedures are described in the supplemental materials and methods.…”