Abstract: Abstract: Objective To investigate the effects of microRNAs (miRNAs) on the proliferation and apoptosis of colorectal cancer HCT116 cells and its mechanism. Methods The FBXW7 mRNA and protein levels were detected by realtime quantitative PCR and Western blot assay in 20 clinical specimens. After predicted by TargetScan tool, verified by quantitative PCR and luciferase activity assay, the miRNAs combined with FBXW7 were identified. The FBXW7 mRNA and protein levels were detected after transient transfection of miR-223 and its control miCtr and inhibitor (inhibitor) into HCT116 cells. CCK-8 and flow cytometry were used respectively to detect the cell viability and apoptosis rate. In addition, the level of miR-223 and the number of apoptosis were detected after down-regulating the expression of Notch3 by siRNA. Results The FBXW7 mRNA and protein levels were lower in colorectal tumor tissues than those in adjacent tissues (P＜ 0.05). It was predicted and confirmed that miR-223 and miR-25 could specifically bind to FBXW7 gene. After transfection of miR-223 in HCT116 cells, the FBXW7 mRNA and protein levels were down-regulated (P＜0.01), the cell viability was increased (P＜0.05) and the number of apoptotic cells was decreased (P＜0.01). After down-regulation of Notch3 pathway, miR-223 mRNA levels decreased (P＜0.001), FBXW7 mRNA levels increased (P＜0.01) and apoptotic cells decreased (P＜ 0.05). Conclusion Notch pathway upregulates the miR-223 level, which inhibits the expression of FBXW7 and eventually promotes the proliferation and inhibits its apoptosis of colon cancer cell line HCT116.

Key words: colonic neoplasms, FBXW7, microRNA, viability, cell apoptosis, Notch pathway