Evaluation of ¹¹¹In-labeled Anginex as Potential SPECT Tracer for Imaging of Tumor Angiogenesis

Abstract

Angiogenesis is a prerequisite for solid tumors to grow and metastasize, providing oxygen and nutrients to the tumor site. The protein galectin-1 has been identified to be overexpressed on tumor vasculature and represents an interesting target for anti-angiogenic therapy, as well as in molecular imaging. Therefore, the galectin-1-binding peptide Anginex was modified for radiolabeling using ¹¹¹In. In vitro, ¹¹¹In-Ax showed significantly more binding to galectin-1-positive EC-RF24 and MDA-MB-231-LITG cells than to galectin-1-negative LS174T cells and association with EC-RF24 cells was reduced in the presence of excess native Anginex. However, ex vivo biodistribution profiles showed little tumor uptake of ¹¹¹In-Ax and extensive accumulation in non-target organs. Although this study shows the ease of modification of the therapeutic peptide Anginex and favorable characteristics in vitro, in vivo assessment of the tracer revealed negligible tumor targeting. Hence, the strategy we employed lends little support for successful non-invasive imaging of tumor angiogenesis using this peptide.