Rapamycin Combined With ACNU Increase The Inhibitory Effect On Human U87-MG Glioma Cells

Objective To study the inhibition of U87-MG human glioma cell line porliferation by combining rapamycin and ACNU in vitro and the possible mechanism.Method The proliferation ability of U87-MG after treatment of rapamycin and/or ACNU were determinde by MTT assay.The combined effect of rapamycin plus ACNU in inhibition of U87-MG was analyzed by isobolographic analysis.The cycle distrubition and apoptosis of U87-MG cells were evaluated by flow cytometry. Acridine orange and MDC staining were conducted to detect the autophagy of U87-MG cells.Ultrastructure of the cells was observed by transmission electron microscope.Results As MTT assay showed,the tumor cell survival rate was inhibited significantly afer treatment of rapamycin alone or plus ACNU. IC50 was 0.726±0.063umol/L in the rapamycin group,26.9±2.3ug/ml in the ACNU group.The isobolographic analysis demonstrated that rapamycin and ACNU in combination produced a synergistic effect during treatment. Although ACNU significantly induced apoptosis in U87-MG cells compaired with notreatment group,no significant apoptosis was detected in rapamycin-treated tumor cells.Gi phase cell cycle arrest was founded in rapamycin group.More apoptosis cells and G1 phase cell cycle arrest were detected in combining rapamycin and ACNU group. Staining of acridine orange and MDC demonstrated that rapamycin could induce autophagy alone.And the effect would be enhanced by treated with ACNU.Autophagosomes and apoptosis were detected in the same tumor cell in combination group by transmission electron microscope.Conclusions The combination effect of rapamycin and ACNU had synergistic interactions in treating U87-MG glioma cells.