Alkaline ceramidase 3 promotes growth of hepatocellular carcinoma cells via regulating S1P/S1PR2/PI3K/AKT signaling

Objective: Hepatocellular carcinoma (HCC) is one of the cancer types with poor prognosis. To effectively treat HCC, new molecular targets and therapeutic approaches must be identified. Alkaline ceramidase 3 (Acer3) hydrolyzed long-chain unsaturated ceramide to produce free fatty acids and sphingosine. However, whether and how Acer3 modulates progression of HCC remains largely unknown. Methods: Acer3 mRNA levels in different types of human HCC samples or normal tissues were determined from Gene Expression across Normal and Tumor tissue (GENT) database. The expression level of Acer3 in human HCC cell lines were examined by western blot. Overall survival and disease-free survival of HCC patients were determined by Kaplan-Meier analysis. Effects of Acer3 knockdown by lentivirus infection were evaluated on cell growth and apoptosis. The mechanisms involved in HCC cells growth and apoptosis were analyzed by western blot. Results: In silico analysis of TCGA databases of HCC patients showed that the expression of Acer3 significantly inversely correlates with the overall and disease-free survival of HCC patients. Knockdown expression of Acer3 resulted in decreased cell growth and increased apoptosis. Notably, inhibition of Acer3 resulted in intracellular exhaustion of Sphingosine-l-phosphate (S1P) and inhibited activation of S1PR2/PI3K/AKT signaling. Finally, knockdown of Acer3 induced up-regulation of Bax and down-regulation of Bcl-2. Conclusions: Our study suggests that Acer3 contributes to HCC propagation, and suggests that inhibition of Acer3 may be novel strategy for treating human HCC.