SMPD1 and hepatocellular carcinoma: As evident from Table 1, comparing the expression of genes in HCC to normal liver in the Oncomine database revealed that two of the key enzymes involved in sphingolipid metabolism were downregulated in HCC samples - the SMPD1 gene, which encodes ASM, and the SGPP1 gene, which encodes S1P phosphatase.