The role of cancer stem cells in the acquired resistance to cisplatin of human osteosarcoma cell line MG63

Objective To investigate the role of cancer stem cells (CSC) in the acquired resistance to cisplatin (CDDP) of human osteosarcoma cell line MG63.Methods CDDP-resistant human osteosarcoma cell line MG63 (MG63/CDDP) was established in vitro by exposure to high and gradually increased dose of cisplatin (1,3,5 mg/L).The proliferation and sensitivity to CDDP of MG63/CDDP before and after application of As2O3 (0.20 mg/L) were tested using methyl thiazol tetrazolium (MTT) assay.Real-time quantitative polymerase chain reaction (Real-time PCR) was employed to investigate the expression of let-7,microRNA (miR)-200c and sex determining region Y-box 2 (SOX-2) in MG63/CDDP cells before and after application of As2O3.Results (1) In the presence of CDDP (3 mg/L),the growth rate of MG63/CDDP was significantly higher compared with MG63 cells (P ＜0.01).It was also demonstrated that MG63/CDDP treated by CDDP developed similar proliferation to MG63 cells without treatment of CDDP (P ＞ 0.05).The IC50 of MG63 and MG63/CDDP cells to CDDP were about 6.3 mg/L and 78.9 mg/L respectively and the resistance index was about 12.52.(2) The resistance of MG63/CDDP cells to CDDP was reduced by treatment of As2O3 (0.20 mg/L) with reversed multiples of 3.39 and relative reversed efficiency of 76.6％.(3) MG63/CDDP cells expressed reduced level of let-7 and miR-200c (P ＜ 0.05) and elevated expression of SOX-2 (P ＜0.01) in comparison with MG63 cells.(4) After treatment of As2O3,MG63/CDDP cells developed increased expression of let-7 and miR-200c (P ＜ 0.05) and decreased level of SOX-2 (P ＜ 0.05).Conclusion CSC is a possible mechanism accounting for the acquired resistance of MG63/CDDP to CDDP. Key words: Osteosarcoma;  Drug resistance;  Cisplatin ;  Cancer stem cell