TNF-α promotes the malignant transformation of intestinal stem cells through the NF-κB and Wnt/β-catenin signaling pathways

Cancer stem cells are responsible for tumorigenesis, progression, recurrence and metastasis. Intestinal stem cells (ISCs) are regarded as the origin of intestinal neoplasia. Inflammation also serves an important role in intestinal neoplasia. To explore the molecular mechanisms underlying the inflammation-mediated induction of intestinal tumorigenesis, the present study investigated the function of tumor necrosis factor (TNF)-alpha in the malignant transformation of ISCs. NCM460 spheroid (NCM460s) cells with higher expression of stem cell genes, such as Oct4, Nanog, Sox2 and Lgr5, and with a higher ratio of CD133(+), were obtained from NCM460 cells in serum-free medium. TNF-alpha accelerated cell proliferation, migration and invasion, induced chemotherapy resistance and the epithelial-mesenchymal transition. NF-kappa B and Wnt/beta -catenin pathways were activated in TNF-alpha -induced inflammatory responses, leading to the nuclear translocation of p65 and beta -catenin, as well as promoter activity of NF-kappa B and TCF/LEF transcription factors. It was further demonstrated that TNF-alpha -induced activation of the NF-kappa B and Wnt/beta -catenin signaling pathways, as well as the upregulation of proinflammatory cytokines, were significantly suppressed by p65-knockdown. Notably, PDTC, an inhibitor of NF-kappa B signaling, reversed TNF-alpha -induced activation of the NF-kappa B and Wnt/beta -catenin pathways. A similar role was observed for IWP-2, an inhibitor of Wnt/beta -catenin signaling. Collectively, these results demonstrated that the NF-kappa B and Wnt/beta -catenin pathways were activated to promote TNF-alpha -induced malignant transformation of ISCs, in which these two pathways cross-regulated each other.