MicroRNA-133b Regulates Cell Proliferation and Cell Cycle Progression via Targeting HuR in Colorectal Cancer

Abstract

MicroRNAs (miRNAs/miRs) have been identified to serve a key role in the development of tumors. However, the role of miR-133b in colorectal cancer (CRC) remains largely unclear. This study will investigate the role and mechanism of miR-133b in CRC. Reverse transcription-quantitative polymerase chain reaction analysis was performed to detect the level of miR-133b in CRC cell lines. Bioinformatics software TargetScan predicted the potential target genes of miR-133b, and a dual luciferase reporter assay was used to confirm this. To investigate the role of miR-133b in CRC cells, miR-133b was upregulated or downregulated in CRC cell lines (SW620 and HT-29) by transfecting with a miR-133b mimic or inhibitor, respectively. Subsequently, cell viability was analyzed using MTT assay, whereas cell apoptosis and the cell cycle distribution were analyzed by flow cytometry. In addition, the associated protein levels were detected using western blot analysis. The results demonstrated that miR-133b was significantly downregulated in CRC cell lines when compared with the normal colonic epithelial NCM-460 cell line. Human antigen R (HuR; also termed ELAVL1) was demonstrated to be a direct target of miR-133b and was negatively regulated by miR-133b. HuR was also notably upregulated in the CRC cell lines when compared with the normal control. Transfection of SW620 and HT-29 cells with the miR-133b mimic significantly inhibited cell viability, and induced cell apoptosis and G1 phase arrest, while upregulation of HuR demonstrated the opposite effects. Furthermore, the present data demonstrated that the miR-133b mimic significantly enhanced the protein levels of p21 and p27, and downregulated cyclin D1 and cyclin A levels in SW620 and HT-29 cells; the opposite effects were observed following treatment with the miR-133b inhibitor. In conclusion, the data indicate that miR-133b suppressed CRC cell growth by targeting HuR.