Chloroquine Enhances Rapamycin-induced Apoptosis in MG63 Cells.

We previously showed that the use of autophagy inhibitors in combination with chemotherapy can enhance anticancer effects in sarcoma cell lines. In this study, we investigated the combined effect of the autophagy inhibitor chloroquine and the mTOR inhibitor rapamycin on MG63 osteosarcoma cells.Effects of chloroquine and/or rapamycin on cell proliferation were assessed by WST-1 assays. Effects of chloroquine and/or rapamycin on the mTOR pathway components, autophagy, and apoptosis were investigated by western blot, flow cytometry, and fluorescence microscopy using immunocytochemical staining of LC3 and Annexin V-FITC/propidium iodide.Rapamycin suppressed cell growth and inhibited the mTOR pathway. Rapamycin promoted autophagy by blocking the mTOR pathway, and chloroquine enhanced apoptosis by blocking autophagy.Chloroquine enhances the effects of rapamycin in inducing apoptosis via autophagy inhibition in MG63 cells. Thus, the combined therapy of chloroquine and rapamycin may be a potent treatment for osteosarcoma.