BACKGROUNDEndometrial carcinoma is one of the most common female tract genital malignant tumors. Nifedipine, an L-type calcium channel antagonist can inhibit cell proliferation of carcinomas. Recent studies indicated that a rise in the free cytosolic calcium ([Ca(2+)](c)) was a potent inducer of autophagy. Here, we investigated the relationship between nifedipine and autophagy in Hec-1A cells.

METHODSCells were cultured with nifedipine (10 µmol/L) and harvested at different times for counting cell number. MTT assay was applied to evaluate the cell viability and transwell assay to reveal cell migration. Apoptotic cells were detected with annexin V/PI assay. Then cells were treated with 3-methyladenine (3-MA) (2.5 mmol/L) for 0, 5, 15, 30, 60, and 120 minutes and the expression of the L-type calcium channel alpha1D (Cav1.3) protein was detected. At last, cells were cultured and assigned to four groups with different treatment: untreated (control group), 10 µmol/L nifedipine (N group), 2.5 mmol/L 3-MA (3-MA group), and 10 µmol/L nifedipine plus 2.5 mmol/L 3-MA (N+3MA group). Autophagy was detected with GFP-LC3 modulation by fluorescent microscopy, and expression of the autophagy-associated proteins (LC3, Beclin1 and P70s6K) by Western blotting and monodansylcadaverine (MDC) labeled visualization.

RESULTSProliferation of Hec-1A cells was obviously suppressed by nifedipine compared with that of the untreated cells for 24, 48, and 96 hours (P = 0.000 for each day). The suppression of migration ability of the nifedipine-treated cells (94.0 ± 8.2) was significantly different from that of the untreated cells (160.00 ± 9.50, P = 0.021). The level of early period cell apoptosis induced by nifedipine was (2.21 ± 0.19)%, which was (2.90 ± 0.13)% in control group (P = 0.052), whereas the late period apoptosis level reached (10.38 ± 0.96)% and (4.40 ± 0.60)% (P = 0.020), respectively. The 3-MA group induced a slight increase in the Cav1.3 levels within 15 minutes, but significantly attenuated the Cav1.3 levels after 30 minutes. There were more autophagic vacuoles labeled by MDC in the N group (20.63 ± 3.36) than the control group (6.29 ± 0.16, P = 0.015). GFP-LC3 localization revealed that the LC3 levels of cells in 3-MA group, N+3MA group, 3-MA group were 2.80 ± 0.29, 2.30 ± 0.17, and 1.80 ± 0.21, respectively. Cells in the N group showed significant augmentation of autophagy (P < 0.05). Western blotting analysis confirmed the down-regulation of LC3 levels in 3-MA group (0.85 ± 0.21) and N+3MA group (1.21 ± 0.12) compared with nifedipine treatment (2.64 ± 0.15, P < 0.05). The annexin-V-FITC/PI assay showed that the level of early period cell apoptosis induced in the N+3-MA group ((11.22 ± 0.91)%) differed significantly from that of the control group ((2.51 ± 0.70)%) and N group ((3.47 ± 0.39)%). Similarly, the late period level of the N+3-MA group ((55.19 ± 2.51)%) differed significantly from that of the control group ((15.81 ± 1.36)%) and the N group ((22.09 ± 2.48)%, P < 0.05). The down-regulated expression of P70s6k and up-regulated expression of the Beclin1 revealed significant differences between the N+3-MA group and control group (P = 0.025; Beclin1: P = 0.015).

CONCLUSIONSProliferation and migration in vitro of endometrial carcinoma Hec-1A cells are significantly suppressed by nifedipine. The nifedipine leads autophagy to oppose Hec-1A cells apoptosis. Autophagy inhibition by 3-MA leads down-regulation of Cav1.3 and enhances nifedipine-induced cell death. The nifedipine-induced autophagy is linked to Beclin1 and mTOR pathways.