Crosstalk between apoptosis and autophagy in prostate epithelial cells under androgen deprivation.

Abstract

The present study investigated the molecular mechanism of apoptosis and autophagy in prostate epithelial cells under androgen deprivation (AD). BPH-1 cells were divided into four groups as follows: Control (Cont), AD, autophagy inhibition (AI) and AD + AI groups. Cells in the four groups were treated accordingly, and the level of apoptosis was subsequently measured via flow cytometry. The expression of the microtubule-associated proteins 1A/1B light chain 3 (LC3), caspase-3, poly (ADP-ribose) polymerase 1 (PARP-1) and Beclin-1 proteins of BPH-1 cells was detected at different time points following culture in androgen-deprived medium. Western blotting revealed that the basal levels of the LC3-II protein were detected at 0 h. At 4 h, LC3-II was significantly increased compared with 0 h (P<0.05). Beginning at 20 h, the expression level of the LC3-II protein decreased significantly (P<0.05). Western blotting revealed that beginning at 24 h, the expression level of the PARP-1 protein decreased significantly (P<0.001) and the cleavage fragments of the PARP-1 protein appeared. These results further imply that autophagy serves a cell protective function by mutual inhibition with apoptosis in BPH-1 cells in the removal of androgen conditions. Furthermore, the fragments of the cleaved Beclin-1 protein appeared as 35 and 37 kDa bands. Flow cytometry analysis demonstrated that the rate of cell apoptosis in the AD, AI and AD + AI groups was significantly increased compared with the Cont group (P<0.01). Compared with the AD or the AI groups individually, the rate of cell apoptosis in the AD + AI group was significantly increased (P<0.001). These findings suggest that in the early stage of AD, autophagy has a compensatory function in the cell, whereas in the whole process, autophagy and apoptosis share a mutual antagonism. The Beclin-1-C protein fragment contributed positive feedback to the process of apoptosis, which may be a potential mechanism of AD therapy. Therefore, AD and AI exhibit a synergistic effect to further improve the level of apoptosis.