MiR-346-5p promotes colorectal cancer cell proliferation in vitro and in vivo by targeting FBXL2 and activating the β-catenin signaling pathway.

MiR-346-5p is overexpressed in several cancers, including colorectal cancer (CRC). However, the effects of miR-346-5p on CRC progression have not yet been clarified. In our study, miR-346-5p levels in four CRC cell lines and normal human colon epithelial cells were determined by real-time PCR. SW620 and HCT116 cells were selected and then transfected with miR-346-5p mimic, miR-346-5p inhibitor, or specific siRNAs targeting F-box/LRR-repeat protein 2 (FBXL2). Cell proliferation, cell cycle distribution and cell cycle regulators were examined by CCK-8 assay, flow cytometry, and western blot. The binding of miR-346-5p on 3' untranslated region (UTR) of FBXL2 were verified by dual-luciferase reporter assay. CRC cells were co-transfected with miR-346-5p inhibitor and siFBXL2 to investigate the involvement of FBXL2. Interaction of FBXL2 with forkhead box M1 (FoxM1) was examined by co-immunoprecipitation (Co-IP) assay. The effect of miR-346-5p knockdown on CRC tumorigenesis in vivo was investigated. Here, we found that miR-346-5p overexpression promoted, while miR-346-5p knockdown inhibited cell proliferation and G1-S transition. Inhibition of FBXL2 showed similar effects as miR-346-5p overexpression. Moreover, we verified that FBXL2 was a direct target of miR-346-5p. FBXL2 interacted with FoxM1, and then negatively regulated both FoxM1 and nuclear β-catenin levels. Additionally, FBXL2 knockdown reversed the effects of miR-346-5p inhibitor. In xenograft models, miR-346-5p knockdown significantly inhibited tumor growth, increased FBXL2 expression, and downregulated the levels of FoxM1 and nuclear β-catenin. In conclusion, miR-346-5p may promote CRC growth by targeting FBXL2 and activating the β-catenin signaling pathway. MiR-346-5p may be a novel target in cancer therapy.