Title: MiR‐124‐3p suppresses bladder cancer by targeting DNA methyltransferase 3B
Abstract: This study was aimed to uncover the effects of miR-124-3p on bladder cancer (BC) by regulating DNA methyltransferase 3B. The expressions of miR-124-3p and DNMT3B mRNA in BC tissues and cell lines were detected using RT-PCR. The expression of DNMT3B in cells was determined using Western blot and immunohistochemistry in tissues. In addition, chromogenic in situ hybridization staining was used to measure the expression of miR-124-3p in tissues. BC cells were transfected with miR-124-3p mimics, miR-124-3p inhibitors, DNMT3B siRNAs, and DNMT3B cDNAs + miR-124-3p mimics. Subsequently, cell proliferation, apoptosis, migration, and invasion were measured using CCK-8, the cytometry test, wound healing assay, and Transwell assay, respectively. Finally, the relationship between miR-124-3p and DNMT3B was confirmed using dual luciferase reporter gene assay. MiR-124-3p expression was significantly lower and the level of DNMT3B was significantly higher in BC tissues and cell lines compared with the normal controls. MiR-124-3p was verified to target DNMT3B. The transfection of miR-124-3p mimics and DNMT3B siRNAs down-regulated BC cell proliferation, migration, and invasion, as well as induced cell apoptosis; miR-124-3p inhibitors promoted BC cell proliferation, migration, invasion, and reduced cell apoptosis; and the effects of DNMT3B cDNAs can be compromised by miR-124-3p mimics. Thus, we concluded that miR-124-3p could suppress the proliferation, migration, invasion, and promote apoptosis of BC cells by targeting DNMT3B.