Targeting Wnt/β-Catenin Signaling by TET1/FOXO4 Inhibits Metastatic Spreading and Self-Renewal of Cancer Stem Cells in Gastric Cancer

SIMPLE SUMMARY: Metastasis is the main cause of death for patients suffering gastric cancer. Epithelial-mesenchymal transition (EMT) and cancer stem cells (CSC) are critical attributes of metastasis, both of which are regulated tightly by DNA methylation and Wnt/β-catenin signaling. In this study, we unveiled a novel TET1-FOXO4-β-catenin signaling cascade, in which TET1 inhibits β-catenin activity and its nuclear translocation through transactivating FOXO4 expression. TET1 expression can significantly inhibit EMT and stemness properties of gastric cancer cells, while knocking-down endogenous TET1 induces metastasis and enhances self-renewal of CSCs by activating canonical Wnt signaling, which could be fully rescued by modulating FOXO4 expression. Our data also showed that low expression of TET1 or FOXO4 predicts poor survival of gastric cancer patients, suggesting reactivation of TET1 or FOXO4 might be a novel therapeutic approach to prevent gastric cancer metastasis. ABSTRACT: Metastasis is the main cause of death for patients suffering gastric cancer. Epithelial-mesenchymal transition (EMT) and cancer stem cells (CSC) are critical attributes of metastasis, both of which are regulated tightly by DNA methylation and Wnt/β-catenin signaling. Here, we studied the functions of DNA dioxygenase TET1 in regulating Wnt signaling and in gastric cancer metastasis. Knocking-down and overexpressing TET1 in gastric cancer cells promoted and inhibited metastatic spreading to the liver in immune-deficient mice, respectively. TET1 showed inhibitory effects on metastasis-related features -EMT and CSC, which were reversed by interfering with Wnt/β-catenin signaling. RNA-sequencing identified FOXO4 as a direct transactivating target of TET1. FOXO4 directly interacted with β-catenin and recruited it in the cytoplasm, so as to inhibit β-catenin-mediated transcription of Wnt target genes, including CSC marker EpCAM. Moreover, modulation of FOXO4 could reverse the effects of TET1 manipulation on EMT and self-renewal of CSCs. The analysis with clinical samples confirmed the value of FOXO4 as an independent prognostic predictor of patients’ overall survival. Taken together, regulation of Wnt signaling by TET1/FOXO4 is essential for metastasis-associated cellular properties, and targeting TET1/FOXO4/β-catenin pathway may serve as promising therapeutics in the prevention and treatment of gastric cancer metastasis.