Insulin-like growth factor-I: a key regulator of human cancer risk

Abstract

In this issue of the Journal, Ma et al. (1) report the results of a nested case–control study that show an association between colorectal cancer risk in men and elevated plasma levels of insulin-like growth factor-I (IGF-I) and decreased plasma levels of IGF-binding protein-3 (IGFBP-3). Importantly, this study demonstrates these effects by using plasma samples drawn years before the clinical appearance of the tumor, thus minimizing the chance that plasma levels are influenced by the disease process. This study follows reports demonstrating associations between levels of IGF-I and/or IGFBP-3 and the risk for cancers of the breast, prostate, and lung, suggesting that IGF-I is an important indicator of risk for the most prevalent forms of cancer in West-ern society (2–5). In fact, IGF-I levels appear to have a stronger association than most other risk factors for these common can-cers