We used a spheroid model of colon carcinoma to analyze integrin dynamics as a function of the epithelial-mesenchymal transition (EMT), a process that provides a paradigm for understanding how carcinoma cells acquire a more aggressive phenotype. This EMT involves transcriptional activation of the β6 integrin subunit and a consequent induction of αvβ6 expression. This integrin enhances the tumorigenic properties of colon carcinoma, including activation of autocrine TGF-β and migration on interstitial fibronectin. Importantly, this study validates the clinical relevance of the EMT. Kaplan-Meier analysis of β6 expression in 488 colorectal carcinomas revealed a striking reduction in median survival time of patients with high β6 expression. Elevated receptor expression did not simply reflect increasing tumor stage, since log-rank analysis showed a more significant impact on the survival of patients with early-stage, as opposed to late-stage, disease. Cox regression analysis confirmed that this integrin is an independent variable for these tumors. These findings define the αvβ6 integrin as an important risk factor for early-stage disease and a novel therapeutic candidate for colorectal cancer.
Richard C. Bates, David I. Bellovin, Courtney Brown, Elizabeth Maynard, Bingyan Wu, Hisaaki Kawakatsu, Dean Sheppard, Peter Oettgen, Arthur M. Mercurio
Multivariate analysis for disease-related deaths (Cox regression model)