miR-20a induces cisplatin resistance of a human gastric cancer cell line via targeting CYLD.

The dysregulation of microRNAs (miRNAs) has been demonstrated to contribute to drug resistance of cancer cells, and sustained nuclear factor (NF)kappa B activation is also pivotal in tumor resistance to chemotherapy. In the present study, an essential role for miRNA (miR)-20a was identified in the regulation of gastric cancer (GC) chemoresistance. The expression level of miR-20a was assayed by reverse transcription-quantitative polymerase chain reaction. Additionally, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide was used to detect the drug-resistance phenotype changes of cancer cells associated with upregulation or downregulation of miR-20a. Protein expression levelss were measured by western blotting and immunohistochemistry. Flow cytometry was used to detect cisplatin-induced apoptosis. It was found that miR-20a was markedly upregulated in GC plasma and tissue samples. Additionally, miR-20a was upregulated in GC plasma and tissues from patients with cisplatin (DDP) resistance, and in the DPP-resistant gastric cancer cell line (SGC7901/DDP). The expression of miR-20a was inversely correlated with the expression of cylindromatosis (CYLD). Subsequently, the assessment of luciferase activity verified that CYLD was a direct target gene of miR-20a. Treatment with miR-20a inhibitor increased the protein expression of CYLD, downregulated the expression levels of p65, livin and survivin, and led to a higher proportion of apoptotic cells in the SGC7901/DDP cells. By contrast, ectopic expression of miR-20a significantly repressed the expression of CYLD, upregulated the expression levels of p65, livin and survivin, and resulted in a decrease in the apoptosis induced by DDP in the SGC7901 cells. Taken together, the results of the present study suggested that miR-20a directly repressed the expression of CYLD, leading to activation of the NF kappa B pathway and the downstream targets, livin and survivin, which potentially induced GC chemoresistance. Altering miR-20a expression may be a potential therapeutic strategy for the treatment of chemoresistance in GC in the future.