Effect of PI3K-mediated autophagy in human osteosarcoma MG63 cells on sensitivity to chemotherapy with Gefitinib

Background: Osteosarcoma is one of the most common malignant bone tumor in adolescent. With high malignant degree and poorer prognosis, osteosarcoma seriously influences the prognostic survival of patients. Autophagy which is relatively conservative, is the main means of degrading autologous organelles or proteins in the evolutionary of eukaryocyte, regulating and controlling the cell proliferation and function. Objective: To explore the effect of PI3K-mediated autophagy in human osteosarcoma MG63 cells on sensitivity to chemotherapy with Gefitinib. Methods: MTT and flow cytometry were employed to measure cell proliferation and cell apoptosis of human osteosarcoma MG63 cells treated with Gefitinib combined with autophagy inhibitor 3-methyladenine (3-MA), autophagy promoter rapamycin, PI3K inhibitor LY294002. The expression of intracellular protein and its total mRNA was detected by Western blot and RT-PCR after different drugs treated on MG63 cells. Results and conclusion: Western blot showed that basic autophagy level of MG63 cells was significantly lower than that of osteoblast hFOB cells. MTT, western blot and RT-PCR analysis revealed that the cell proliferation inhibition rate of MG63 cells treated with Gefitinib combined with 3-MA, RAPA, LY294002 were significantly inhibited. Besides, the expressions of autophagy associated proteins and total mRNA in human osteosarcoma cells were enhanced. In addition, the result of flow cytometry demonstrated that Gefitinib alone or combined with other drugs could increase the cell numbers in G1 phase and reduce the cell numbers in S phase. Taken together, our data showed that upregulating the autophagy significantly reduced the sensitivity of MG63 cells to chemotherapy with DDP and DDP induced autophagy of MG63 cells by blocking the cell cycle at G1 phase.