Sphingosine 1‐phosphate (S1P)‐induced autophagy plays a protective role in human prostate PC‐3 cells

Sphingosine 1‐phosphate (S1P) is a platelet‐enriched lysophospholipid (LPL) which regulates various cellular functions through binding and activating a specific family of G protein‐coupled S1P receptors. In general, S1P promotes cell proliferation among cancer cells. Interestingly, our previous studies suggested that S1P inhibited proliferation in PC‐3 cells independent of apoptosis. Moreover, autophagy, a sub‐cellular membranes trafficking process which leads to the degradation and recycling of cytoplasm under starvation stress, was also elevated upon S1P stimulus through S1P 5 activation. In the present study, we intend to investigate the relationship between cell death and autophagy induced by S1P. By using a potent autophagy inhibitor, 3‐methyladenine (3‐MA), we observed that inhibition of S1P‐induced autophagy by 3‐MA leads to a significant decrease of cell numbers as compared to S1P treatment. These results indicate that the autophagy activity induced by S1P treatment plays a protective role in PC‐3 cells.