神經鞘氨醇 1-磷酸鹽導致人類前列腺癌PC-3細胞株產生細胞自噬現象之研究

Abstract

Sphingosine 1-phosphate (S1P), a bioactive sphingolipid is abundant in serum. S1P can induce various responses in many cell types, such as cell proliferation, inflammation, migration, angiogenesis and cell survival through a family of S1P-specific G-protein-couple receptors (S1P1-5). Autophagy, one of main cellular activities, is a cellular degradation pathway which serves an adaptive role to protect cells under starvation or stress situations. Damaged or superfluous cellular proteins and organelles can be engulfed by autophagosomes, then digested when fused with lysosomes, and recycled back into the cytosol to maintain cellular homeostasis. Recently, scientists have begun to consider autophagy as a tumor-suppressing pathway, but the regulatory mechanisms are still controversial. In addition, the relationship between S1P and autophagy remains unclear. Herein, autophagy was characterized by using Western blotting analysis to detect microtubule-associated protein light chain 3-II (LC3-II, an autophagy marker) formation, and to observe the LC3-II molecules re-localization from cytosol to autophagosomes in EGFP-LC3 stably expressing cells by using fluorescence microscopy. These results suggested that S1P induced autophagy in PC-3 cells, a human prostate cancer cell line, is both time- and concentration-dependent. Furthermore, by using chemical inhibitors, Rho family GTPase (Rho, Rac, and Cdc42)-, ERK1/2-, COX-1-, and COX-2-dependent pathways were found to be involved in the induction of autophagy. In conclusion, the results demonstrated the molecular mechanisms of S1P-induced autophagy in PC-3 cells during starvation.