LAUSR

Purpose Today it is known that the gene expression profile of cancer stem cells differs from other cancer cells, which may lead to the resistance to routine treatments. The aim of this study was to investigate the effect of docetaxel (DOC) treatment on CD44+ cell frequency in human gastric cancer (GC) MKN-45 cell line and its effect on expression levels of SIRT1, CXCR4, microRNA (miR)-21, miR-451, and miR-34a that are closely correlated with the chemoresistance or self-renewal of cancer stem cells (CSCs). Methods The cytotoxic effect of DOC on MKN-45 cell line was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT)-assay. The frequency of CD44+ cells was measured by flow cytometry in the treated and control groups. The expression level of SIRT1, CXCR4, miR-21, miR-451, and miR-34a was assessed in DOC-treated and non-treated cells using quantitative real-time PCR. Data were analyzed using Statistical Package for the Social Sciences (SPSS) software. Results The half-maximal inhibitory concentration (IC 50 ) of DOC was 10 μg/ml after 48 h. Flow cytometry showed a significant increase in CD44+ cells after treatment with DOC (94.3%) when compared with non-treated cells (84.6%) ( P  < 0.01). The expression of SIRT1, CXCR4, and miR-21 was up-regulated (1.4-fold, 6.7-fold, and 1.22-fold, respectively, P  < 0.05) in DOC-treated cells relative to non-treated cells, while miR-451 and miR-34a were down-regulated (0.14-fold and 0.36-fold, respectively, P  < 0.05). Conclusion DOC treatment affected CD44+ cell frequency in MKN-45 cell line and induced significant changes in the expression of SIRT1, CXCR4, miR-21, miR-451, and miR-34a that are implicated in stemness and chemo-radioresistance, which might offer new insights for future GC therapies.