IGF-1R, IGF-1 and IGF-2 expression as potential prognostic and predictive markers in colorectal-cancer

Insulin-like growth factors (IGF-1 and IGF-2) and the IGF-1 membrane receptor (IGF-1R) have been found to play a critical role in the carcinogenesis of several tumors, among them colorectal cancer (CRC). To study the prognostic impact of these molecules, a total number of 713 cases of CRC were examined for the expression of IGF-1, IGF-2, and IGF-1R. The results were correlated with other clinicopathological data and clinical follow-up. IGF-1 expression was noted in 53 (7.5%), IGF-2 in 88 (12.6%), and IGF-1R in 698 (99.6%) of the cases. There were significant associations between the two growth factors (P<0.00001), between IGF-1 and Ki-67 proliferation activity (P<0.05), and between IGF-2 and tumor stage (P<0.005). IGF-2 positivity was significantly correlated to a worse clinical outcome (P<0.005) only in univariate, but not in multivariate, survival analysis. A similar trend was obtained for patients with IGF-1-positive CRC, but reached statistical significance only in limited tumor stages (pT1/pT2; P<0.01). Although the synchronous expression of IGF-1, IGF-2, and IGF-1R in a subset of CRC is consistent with an auto-/paracrine loop of cancer cell autostimulation, the prognostic effect of IGF-1 and IGF-2 expression seems to be of limited value. However, the identification of IGF-positive CRC might be beneficial for predictive reasons, as new molecular therapeutic approaches are aimed at the IGF system and related pathways.