Clinical studies of pharmacologic agents targeting the insulin-like growth factor (IGF) pathway in unselected cancer patients have so far demonstrated modest efficacy outcomes, with objective responses being rare. As such, the identification of selection biomarkers for enrichment of potential responders represents a high priority for future trials of these agents. Several reports have described high IGF2 expression in a subset of colorectal cancers, with focal IGF2 amplification being responsible for some of these cases. We defined a novel cut-off value for IGF2 overexpression based on differential expression between colorectal tumors and normal tissue samples. Analysis of two independent colorectal cancer datasets revealed IGF2 to be overexpressed at a frequency of 13% to 22%. An in vitro screen of 34 colorectal cancer cell lines revealed IGF2 expression to significantly correlate with sensitivity to the IGF1R/INSR inhibitor BI 885578. Furthermore, autocrine IGF2 constitutively activated IGF1R and Akt phosphorylation, which was inhibited by BI 885578 treatment. BI 885578 significantly delayed the growth of IGF2-high colorectal cancer xenograft tumors in mice, while combination with a VEGF-A antibody increased efficacy and induced tumor regression. Besides colorectal cancer, IGF2 overexpression was detected in more than 10% of bladder carcinoma, hepatocellular carcinoma and non-small cell lung cancer patient samples. Meanwhile, IGF2-high non-colorectal cancer cells lines displayed constitutive IGF1R phosphorylation and were sensitive to BI 885578. Our findings suggest that IGF2 may represent an attractive patient selection biomarker for IGF pathway inhibitors and that combination with VEGF-targeting agents may further improve clinical outcomes. Mol Cancer Ther; 16(10); 2223–33. ©2017 AACR.
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