Endocannabinoid system and the expression of endogenous ceramides in human hepatocellular carcinoma

The endogenous lipid metabolism network is associated with the occurrence and progression of malignancies. Endocannabinoids and ceramides have demonstrated their anti-proliferative and pro-apoptotic properties in a series of cancer studies. The aim of the present study was to evaluate the expression patterns of endocannabinoids and endogenous ceramides in 67 pairs of human hepatocellular carcinoma (HCC) tissues and non-cancerous counterpart controls. Anandamide (AEA), the major endocannabinoid, was reduced in tumor tissues, probably due to the high expression and activity of fatty acid amide hydrolase. Another important endocannabinoid, 2-arachidonylglycerol (2-AG), was elevated in tumor tissues compared with non-tumor controls, indicating that the biosynthesis of 2-AG is faster than the degradation of 2-AG in tumor cells. Furthermore, western blot analysis demonstrated that cannabinoid receptor 1 was downregulated, while cannabinoid receptor 2 was elevated in HCC tissues, in accordance with the alterations in the levels of AEA and 2-AG, respectively. For HCC tissues, the expression levels of C18:0, 20:0 and 24:0-ceramides decreased significantly, whereas C12:0, 16:0, 18:1 and 24:1-ceramides were upregulated, which may be associated with cannabinoid receptor activation and stearoyl-CoA desaturase protein downregulation. The exact role of endocannabinoids and ceramides in regulating the fate of HCC cells requires further investigation.