[The study of FTY720 on inducing apoptosis and autophagy in multiple myeloma cell line U266]

To investigate the effects of FTY720, a new immunosuppressive agent, on apoptosis and autophagy in multiple myeloma(MM) cell line U266 and to clarify its molecular mechanism.

U266 cells were treated with 0, 2.5, 5.0, 10.0 and 20.0 µmol/L FTY720 for 24 hours, and the cell viability was assayed by CCK-8 method. Then U266 cells were treated with 20.0 µmol/L FTY720 for 0, 2, 6 and 24 hours, the cell viability was tested. The apoptotic rates induced by different doses and time points of FTY720 were tested by flow cytometry separately. The expression of LC3B was detected by Western blot after U266 cells treated with different doses of FTY720 to see autophagy. U266 cells were treated with FTY720 ± Bafilomycin A1, an inhibitor of autophagy, for 24 hours, then the cell viability and apoptotic rates were tested. Meanwhile the expression of survivin, anti-apoptotic factors, were tested by Western blot.

The cell viability and the apoptotic rates were inhibited significantly by FTY720 (P < 0.05) in time-dependent and dose-dependent manner. The expression of LC3B-II increased significantly in a dose-dependent manner, it indicated that the autophagy was induced by FTY720. Bafilomycin A1 could rescue the cell viability and apoptotic rates in U266 cells treated with FTY720, and it could also rescue the expression of survivin decreased by FTY720.

FTY720 can cause apoptosis and autophagy of U266 cells. The autophagy promote the apoptosis, which maybe due to the degradation of anti-apoptotic factors such as survivin or their upstream factors in lysosomes through autophagy.