MicroRNA-152 suppresses cell proliferation and tumor growth of bladder cancer by targeting KLF5 and MKK7

Abstract

B ackground: In bladder cancer, miR-152 has been reported to be downregulated and accompanied by high DNA methylation. However, the molecular mechanisms underlying miR-152 in bladder cancer tumorigenesis remain unknown. M ethods: The expressions of miR-152 in human bladder cancer cell lines (J82, 5637, and T24) and a human bladder epithelial cell line (SV-HUC-1) were compared. The expression of miR-152 was observed after adding DNA methylation inhibitor 5-Aza-dC or after knocking down the major DNA methyltransferase DNMT1. The bladder cancer cell viability was determined using an MTT assay, and the colony formation rate was determined using a colony formation assay. The effects of miR-152 overexpression on cell proliferation and tumor growth were observed in vitro and in vivo. The interactions among miR-152, KLF5, and MKK7 were determined using a luciferase reporter assay. R esults: MiR-152 was downregulated in bladder cancer cell lines in comparison with normal ones. The expression of miR-152 was significantly promoted after adding 5-Aza-dC or after knocking down DNMT1. The overexpression of miR-152 suppressed cell proliferation and tumor growth both in vitro and in vivo. MiR-152 inhibited KLF5 and MKK7 expression by binding with 3’ untranslated regions of their mRNAs. Meanwhile, the overexpression of KLF5 induced MKK7 expression by increasing the transcriptional activity of MKK7. The simultaneous overexpression of miR-152 and KLF5 reversed the inhibition of cell proliferation caused by miR-152 overexpression alone. C onclusions: Our findings suggest that miR-152 acts as a tumor suppressor in bladder cancer, and the overexpression of miR-152 may be a potential strategy for treating bladder cancer. K eywords: cell proliferation, bladder cancer, DNA methylation, miR-152, transcription factor