Epigenetic Suppression of miR-137 Induces RNF4 Expression, Facilitating Wnt Signaling in Colorectal Cancer.

Abstract

Colorectal cancer (CRC) is a significant health issue worldwide. Recent studies highlight the critical role of miRNAs in CRC development, particularly miR-137, which acts as a key tumor suppressor. Despite its known role, further exploration of miR-137's downstream signaling is needed to understand its biology and therapeutic potential. We examined the methylation status of miR-137 using one TCGA data and three GEO data sets. A clinical validation cohort of 78 samples was analyzed using MSP for miR-137 promoter methylation. Various in vitro molecular/cellular and animal experiments were conducted to elucidate miR-137's role in CRC. Bioinformatic analysis indicated frequent methylation of miR-137 in CRC tissues, correlating with suppressed expression. EZH2-mediated H3K27 trimethylation silences miR-137 in CRC cells by increasing chromatin compaction, reversible by EZH2 siRNA or inhibitor GSK343. miR-137 inhibits CRC cell proliferation, migration, invasion, and xenograft tumor growth, confirming its tumor-suppressive role. Using the miRWalk repository showed that miR-137 regulates the Wnt signaling pathway by reducing typical protein expression in HCT116 and SW480 cells. miR-137 directly targets RNF4, leading to its downregulation at transcriptional and protein levels, with an observed inverse correlation in CRC tissues. miR-137 accelerates c-Myc and β-catenin degradation by inhibiting RNF4, impacting protein stability and Wnt pathway inhibition. miR-137 is epigenetically silenced through DNA methylation and EZH2-mediated H3K27 trimethylation. It regulates the Wnt signaling pathway by targeting RNF4, leading to c-Myc and β-catenin destabilization. Restoring miR-137 or inhibiting RNF4 suppresses CRC cell proliferation, migration, invasion, and tumor growth, highlighting its therapeutic potential in CRC.