Tumor suppressor microRNA-18a regulates tumor proliferation and invasion by targeting TBPL1 in colorectal cancer cells

Recent advances in the understanding of microRNA have rendered microRNAs (miRNAs) a compelling novel class of biomarker in cancer biology. However, the specific function of miRNA-18a (miR-18a) in colorectal cancer (CRC) remains unclear. In the present study, the role of miR-18a in the carcinogenesis of CRC was investigated. miR-18a expression was assessed in CRC specimens and cell lines using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The targets of miR-18a were predicted using bioinformatics tools. Luciferase reporter assays were used to confirm the functional association between miR-18a and its target genes. The effect of miR-18a on cell proliferation, invasion and migration was confirmed in vitro by a methylthiazol tetrazolium assay, cell invasion assay, and wound healing assay. Gene and protein expression was examined using RT-qPCR and western blotting, respectively. It was demonstrated that the expression of miR-18a in CRC tissues and cell lines was markedly lower than in normal control tissues and cells, respectively. In addition, miR-18a inhibited cell proliferation, invasion and migration in CRC cells. Moreover, TATA box-binding protein-like protein 1 (TBPL1) was identified as a potential target gene of miR-18a in the bioinformatics analysis and luciferase reporter assays, and miR-18a directly inhibited TBPL1 expression by targeting its 3'-untranslated region. Furthermore, TBPL1 was downregulated and inversely correlated with miR-18a expression in tissues. These findings demonstrate that miR-18a exhibits a protective role in CRC via inhibiting proliferation, invasion and migration of CRC cells by directly targeting the TBPL1 gene.