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OBJECTIVE The aim of this study was to investigate the effects of micro ribonucleic acid (miR)-490-5p on the proliferation and apoptosis of colon cancer cells, and to explore its potential mechanism. PATIENTS AND METHODS The mRNA expression of miR-490-5p in 30 pairs of colon cancer tissues and adjacent normal tissues was detected via reverse transcription-polymerase chain reaction (RT-PCR). Human colon cancer SW480 cell lines were cultured in vitro and divided into Control group and miR-490-5p overexpression group (miR-490-5p mimic group). The nonsense sequence and miR-490-5p mimic were transfected using liposome transfection technique into colon cancer cells in control group and miR-490-5p mimic group, respectively. Cell proliferation and apoptosis in each group were then observed. At the same time, the effect of miR-490-5p on the growth of colon cancer in vivo was explored using subcutaneous tumorigenesis assay. The protein expressions of extracellular signal-regulated kinase (ERK)1/2 signaling pathway and cyclin-dependent kinase 1 (CDK1) were determined via Western blotting. Furthermore, immunohistochemical staining was performed to verify the protein expression of CDK1 in vivo. RESULTS The expression of miR-490-5p in colon cancer tissues was significantly lower than that in adjacent normal tissues (p<0.05). After transfection with miR-490-5p mimic in vitro, EdU staining and colony formation assay showed that the proliferation ability of SW480 cells was significantly weakened (p<0.05). Meanwhile, the number of colonies in miR-490-5p mimic group was markedly less than that in Control group (p<0.05). The results of Western blotting revealed that overexpression of miR-490-5p remarkably up-regulated the Bax/Bcl-2 and C-Caspase3/T-Caspase3 ratios in cancer cells (p<0.05). Subsequent results indicated that the subcutaneous tumorigenesis of colon cancer cells was markedly inhibited by overexpression of miR-490-5p (p<0.05). According to the results of Western blotting, the activation of ERK signaling pathway and the protein expression of CDK1 were significantly suppressed by overexpression of miR-490-5p (p<0.05). In vivo experiments further revealed that the protein expression of CDK1 in colon cancer tissues increased significantly (p<0.05). CONCLUSIONS MiR-490-5p was found lowly expressed in colon cancer patients. In addition, overexpression of miR-490-5p inhibited the proliferation and promoted the apoptosis of colon cancer cells via down-regulating CDK1 both in vitro and in vivo.