miR-522-3p Promotes Tumorigenesis in Human Colorectal Cancer via Targeting Bloom Syndrome Protein.

miR-522-3p is known to degrade bloom syndrome protein (BLM) and enhance expression of other proto-oncogenes, leading to tumorigenesis. This study aimed to investigate the molecular mechanisms of miR-522-3p in human colorectal cancer (CRC) cells. Expressions of miR-522-3p in CRC and adjacent tissues, as well as in normal human colon epithelial cell line (FHC) and five CRC cell lines, were detected. Human CRC cell lines, HCT-116 and HT29, were transfected with miR-522-3p mimic, inhibitor, or scrambled controls. Then cell viability, apoptosis, cell cycle progression, and the expressions of c-myc, cyclin E, CDK2, and BLM were assessed. It was found that miR-522-3p was highly expressed in CRC tissues when compared to adjacent nontumor tissues and was highly expressed in CRC cell lines when compared to FHC cells. miR-522-3p overexpression promoted cell viability, reduced apoptotic cell rate, arrested more cells in the S phase, and upregulated c-myc, cyclin E, and CDK2 expression. BLM was a target gene of miR-522-3p, and miR-522-3p suppression did not exert antiproliferative and proapoptotic activities when BLM was silenced. These findings demonstrate that miR-522-3p upregulation negatively regulates the expression of BLM, with upregulation of c-myc, CDK2, and cyclin E, and thereby promoting the proliferation of human CRC cells.