miR-186-5p Prevents Hepatocellular Carcinoma Progression Through Targeting METTL3 to Regulate m6A-Mediated Stabilization of FSTL5

Abstract Background: Hepatocellular carcinoma (HCC) processes in multi-steps which involves the sophisticated interactions of genetics, epigenetics, and transcriptional changes. According to before investigations, methyltransferase-like 3 (METTL3)-mediated m6A modification regulates the development of various cancers by regulating gene stability. However, the studies focusing on miRNA’s regulatory effect of N6-methyladenosine (m6A) modification on HCC progression are still limited. Methods: Immunochemistry (IHC) staining detected the histopathological changes in the tumor tissues. Cell Counting Kit-8 (CCK-8), clone formation, and transwell assay investigated the changes in cancer cell proliferation, invasion, and migration. The RNA m6A level was confirmed by methylated RNA immunoprecipitation. The RNA stability assay indicated the half-life (t1/2) of RNA in HCC cells. The prognosis of the indicated patients’ cohort was analyzed using the cancer genome atlas (TCGA) datasets. Luciferase report analysis was used to study the potential binding between microRNA (miRNA) and mRNA. A mice tumor transplant model was further established to study the changes in tumor progression. Results: Follistatin-like 5 (FSTL5) was found to be significantly downregulated in HCC, and it inhibited the further progression of HCC. The RNA stability analysis indicated that the mRNA t1/2 gene of HCC cells was shortened. Besides, METTL3 reduced the stability of FSTL5 mRNA in a m6A-YTH domain family 2(YTHDF2)-dependent manner. Functional experiments revealed that the downregulated METTL3 inhibited the HCC progression by up-regulating FSTL5 in vitro and in vivo. Luciferase report analysis confirmed that miR-186-5p directly targeted the METTL3. Additionally, miR-186-5p inhibited the proliferation, migration, and invasion of HCC cells by downregulating METTL3. We identified that miR-186-5p prevented the HCC progression by targeting METTL3 to regulate m6A-mediated FSTL5 stabilization. Conclusions: The miR-186-5p/METTL3/YTHDF2/FSTL5 axis perhaps point out a new direction for the targeted therapy of HCC.