Epithelial–Mesenchymal Transition (EMT) Induced by TNF-α Requires AKT/GSK-3β-Mediated Stabilization of Snail in Colorectal Cancer

Abstract

Chronic inflammation-promoted metastasis has been considered as a major challenge in cancer therapy. Pro-inflammatory cytokine TNFa can induce cancer invasion and metastasis associated with epithelial-mesenchymal transition (EMT). However, the underlying mechanisms are not entirely clear. In this study, we showed that TNFa induces EMT in human HCT116 cells and thereby promotes colorectal cancer (CRC) invasion and metastasis. TNFa-induced EMT was characterized by acquiring mesenchymal spindle-like morphology and increasing the expression of N-cadherin and fibronectin with a concomitant decrease of E-cadherin and Zona occludin-1(ZO-1). TNFa treatment also increased the expression of transcription factor Snail, but not Slug, ZEB1 and Twist. Overexpression of Snail induced a switch from E-cadherin to Ncadherin expression in HCT116 cells, which is a characteristic of EMT. Conversely, knockdown of Snail significantly attenuated TNFa-induced EMT in HCT116 cells, suggesting that Snail plays a crucial role in TNFa-induced EMT. Interestingly, exposure to TNFa rapidly increased Snail protein expression and Snail nuclear localization but not mRNA level upregulation. Finally, we demonstrated that TNFa elevated Snail stability by activating AKT pathway and subsequently repressing GSK-3b activity and decreasing the association of Snail with GSK-3b. Knockdown of GSK-3b further verified our finding. Taken together, these results revealed that AKT/GSK-3b-mediated stabilization of Snail is required for TNFa-induced EMT in CRC cells. Our study provides a better understanding of inflammation-induced CRC metastasis.