Tumor necrosis factor-α-inducing protein of Helicobacter pylori promotes epithelial-mesenchymal transition and cancer stem-like cells properties via activation of Wnt/β-catenin signaling pathway in gastric cancer cells

Tipi +/- (TNF-i +/- inducing protein) of H. pyloriinduces EMT and the emergence of gastric CSCs in vitro. Tumor necrosis factor-alpha-inducing protein (Tip alpha) is a newly identified toxin that promotes the inflammation and carcinogenesis caused by Helicobacter pylori. However, its mechanism of pathogenesis is still unclear. To investigate the carcinogenic mechanisms of Tip alpha, SGC7901 cells and SGC7901-derived cancer stem-like cells (CSCs) were stimulated by recombinant Tip alpha with or without Wnt/beta-catenin signaling inhibitor XAV939. qRT-PCR and Western blotting were employed to detect expression of epithelial-mesenchymal transition (EMT), CSCs markers and downstream target genes of this signaling pathway. The cell migration ability was measured by wound healing assay and transwell assay. Our results indicated that Tip alpha promoted CSC properties of SGC7901 spheroids, including increased expression of CSC specific surface markers CD44, Oct4 and Nanog and an increased capacity for self-renewal. Tip alpha activated Wnt/beta-catenin signaling in both SGC7901 cells or CSCs. Furthermore, Tip alpha induced the EMT and increased the expressions of downstream target genes of this signaling, including c-myc, cyclin D1 and CD44. However, XAV939 pretreatment inhibited Tip alpha-induced EMT and CSC properties in SGC7901 cells or CSCs. These results suggest that Tip alpha promotes EMT and CSC-like properties in gastric cancer cells through activation of Wnt/beta-catenin signaling pathway, thereby accelerating the progression of gastric cancer.