MiR-6511b-5p suppresses metastasis of pMMR colorectal cancer through methylation of CD44 by directly targeting BRG1

PURPOSE: Distal metastases are a major cause of poor prognosis in colorectal cancer patients. Approximately 95% of metastatic colorectal cancers are defined as DNA mismatch repair proficient (pMMR). Our previous study found that miR-6511b-5p was downregulated in pMMR colorectal cancer. However, the mechanism of miR-6511b-5p in pMMR colorectal cancer metastases remain unclear. METHODS: We first used quantitative real-time PCR to evaluate the role of miR-6511b-5p in colorectal cancer. Second, we conducted invasion assays and wound healing assays to investigate the role of miR-6511b-5p and CD44 in colorectal cancer cells metastases. Third, luciferase reporter assay, in situ hybridization (ISH), and immunohistochemistry assays were performed to study the relationship between miR-6511b-5p and BRG1. Finally, real-time quantitative PCR, immunohistochemistry, and chromatin immunoprecipitation (ChIP) assays were performed to analyze the relationship between BRG1 and CD44 in colorectal cancer. RESULTS: We found that lower expression of miR-6511b-5p appeared more often in pMMR colorectal cancer patients compared with dMMR (mismatch repair deficient) cases, and was positively correlated with metastases. In vitro, overexpression of miR-6511b-5p inhibited metastasis by decreasing CD44 expression via directly targeting BRG1 in colorectal cancer. Furthermore, BRG1 knockdown decreased the expression of CD44 by promoting CD44 methylation in colorectal cancer cells. CONCLUSION: Our data suggest that miR-6511b-5p may act as a promising biomarker and treatment target for pMMR colorectal cancer, particularly in metastatic patients. Mechanistically, miR-6511b-5p suppresses invasion and migration of colorectal cancer cells through methylation of CD44 via directly targeting BRG1. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12094-022-02845-4.