Objective: To investigate the influence of autophagy on the survival and proliferation of multiple myeloma (MM) cells.
Methods: Multiple myeloma (MM) cell line U266 cell autophagy was induced by serum-free culture condition, and adding rapamycin or 3-MA respectively. The cells proliferation was observed. U266 cells, lymphoma cell Jurket under normal culture condition, and serum-free cultured Jurket cell were used as control group. The proliferation and apoptosis of cells were determined by CCK8 and flow cytometry, respectively. MDC staining were employed to detect the autophagy. The mRNA expression of Mtor and Beclin1 gene of U266 cells were assayed by RT-PCR. Protein LC3I/LCII and LAMP1 was analyzed by western blot.
Results: There was low level of autophagy in U266 cells, sera starvation increased the level of autophagy. Rapamycin upregulated autophagy of the U266 cells and stimulated their proliferation. But the autophagy level of sera starvation and rapamycin group declined when culture for 96h.3-MA had the same effects on U266 cells, although it was on 24 h. But rapamycin and 3-MA could inhibit cell proliferation under normal culture condition. Compared with normal culture condition, apoptosis of U266 cells increased significantly after 24h incubation in medium without sera \[(1.33 ± 0.09)% and (17.90 ± 1.46)%, respectively\] (P < 0.01). Rapamycin and 3-MA could inhibit the serum-free induced apoptosis \[(6.23 ± 0.12)% and (6.97 ± 0.03)%, respectively\](P < 0.01), but cell apoptosis was at the same level after 72 hour incubation \[(30.37 ± 0.27)%, (30.13 ± 1.93)% and (28.57 ± 2.83)%, respectively\] (P > 0.05). However, apoptosis of U266 cells decreased to 18.7% and 12.6% after removal of rapamycin and 3-MA.
Conclusion: There is basically level of autophagy in MM cells which is higher than those in the Jurkat cells. Both Rapamycin and 3-MA can inhibit the cells proliferation under normal culture condition. Up-regulated autophagy promotes survival and proliferation of MM cells under sera deletion. Rapamycin strengthens this effect with limited duration. 3-MA has dual effects on cell autophagy.