Effects of endosulfan on hepatoma cell adhesion: Epithelial-mesenchymal transition and anoikis resistance

Abstract

Endosulfan is an organochlorine pesticide commonly used in agriculture yet classified by the Stockholm Convention in 2011 as a persistent organic pollutant (POP). Its potential toxicity makes its continued use a major public health concern. Despite studies in laboratory animals, the molecular mechanisms underlying the carcinogenic effects of endosulfan in human liver remain poorly understood. In this study, we investigated the phenotypical effects of endosulfan on HepG2 liver cells. First, we found that endosulfan disrupted the anoikis process. Indeed, cells exposed to endosulfan were initially sensitized to anoikis and thereafter recovered their resistance to this process. This phenomenon occurred in parallel to the induction of the epithelial to mesenchymal (EMT) process, as demonstrated by: (1) reorganization of the actin cytoskeleton together with activation of the FAK signaling pathway; (2) repression of E-cadherin expression; (3) induction of Snail and Slug; (4) activation of the WNT/β-catenin pathway; and (5) induction and reorganization of mesenchymal markers (S100a4, vimentin, fibronectin, MMP-7). Secondly, despite the acquisition of mesenchymal characteristics, HepG2 cells exposed to endosulfan failed to migrate. This incapacity to acquire a motile phenotype could be attributed to a disruption of the interaction between the ECM and the cells. Taken together, these results indicate that endosulfan profoundly alters the phenotype of liver cells by inducing cell detachment and partial EMT as well as disrupting the anoikis process. All these events account, at least in part, for the carcinogenic potential of endosulfan in liver.