K. Miura1, M. Nagahashi1, Y. Hirose1, T. Kobayashi1, J. Sakata1, H. Kameyama1, Y. Shimada1, H. Ichikawa1, K. Takabe2,3, T. Wakai1 1Niigata University Graduate School Of Medical And Dental Sciences,Division Of Digestive And General Surgery,Niigata, NIIGATA, Japan 2Roswell Park Cancer Institute,Breast Surgery, Department Of Surgical Oncology,Buffalo, NY, USA 3University At Buffalo Jacobs School Of Medicine And Biomedical Sciences, The State University Of New York,Department Of Surgery,Buffalo, NY, USA
Introduction: Hepatocellular carcinoma (HCC) is now the third leading cause of cancer deaths worldwide, with over 500,000 people affected. Sphingolipids including sphingosine-1-phosphate (S1P) and ceramide have emerged as key regulatory molecules, controlling various aspects of cancer biology and implicated in the mechanism of action of cancer chemotherapeutics. S1P is known to play important roles in cancer cell survival and progression. We previously demonstrated that S1P is a crucial mediator of cancer-induced angiogenesis and lymphangiogenesis and promote metastasis (Cancer Research 2012). On the other hand, ceramide has been considered to mediate anti-proliferative responses, such as cell growth inhibition, apoptosis induction, senescence modulation and autophagy. Ceramide can be de-acylated to give sphingosine, and sphingosine in turn can be phosphorylated to produce S1P. The dynamic balance between S1P and sphingosine/ceramide is referred to as the “sphingolipid rheostat” and influences cancer cell fate. Although important roles of sphingolipids in cancer progression has been revealed in experimental models, its roles in human HCC patients are yet to be determined. In this study, we measure the levels of sphingolipids including S1P and ceramides in tumor and normal liver tissue by state-of-the-art mass spectrometry.
Methods: Tumor and normal liver tissue were obtained from 20 patients with HCC. Sphingolipids were measured by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). Wilcoxon matched-pairs signed rank test was performed to compare the levels of each sphingolipid between tumor and normal tissue, and P<0.05 was considered as statistically significant.
Results: The levels of sphingolipids including sphingosine, dihydro-sphingosine, S1P, dihydro-S1P, and ceramides were detected successfully in the tumor and normal liver tissue from 20 HCC patients. The levels of S1P and dihydro-S1P in tumor tissue were significantly higher than those in normal liver tissue with almost four-fold increase (P<0.0001 and P<0.0001). Further, sphingosine and dihydro-sphingosine in tumor tissue were also significantly higher than those in normal tissue (P<0.001 and P<0.01). Finally, the levels of each ceramide species (C14:0, C16:0, C18:1, C18:0, C20:0, C22:0, C24:1, C24:0, C26:0) in tumor tissue were significantly higher than those in normal tissue (P<0.0001 for each species).
Conclusion: Our results indicate important role of sphingolipids in HCC. Further study will be required to investigate the distinct roles of each sphingolipid in human patients.