MiR-100 resensitizes docetaxel-resistant human lung adenocarcinoma cells (SPC-A1) to docetaxel by targeting Plk1

MicroRNAs (miRNAs) expression correlates with biological characteristics of both normal cells and cancer cells, but their roles in cancer chemoresistance remain unclear. By microarray analysis, miR-100 was found significantly down-regulated in docetaxel-resistant SPC-A1/DTX cells compared with parental SPC-A1 cells. Ectopic miR-100 expression resensitized SPC-A1/DTX cells to docetaxel by suppression of cell proliferation and induction of cell arrest in G2/M phase and apoptosis. Knock-down of Plk1, which was a direct target of miR-100, yielded similar effects as that of ectopic miR-100 expression. The inverse correlation between miR-100 and Plk1 expression was also detected in nude mice SPC-A1/DTX tumor xenografts and clinical lung adenocarcinoma tissues and was proved to be related with the in vivo response to docetaxel. Thus, our results suggested that down-regulation of miR-100 could lead to Plk1 over-expression and eventually to docetaxel chemoresistance of human lung adenocarcinoma.