PNPLA6 and hepatocellular carcinoma: Although knockdown of PNPLA7 decreases the cellular GPC level in mouse hepatocytes [14], its effect on the GPC level in human HepG2 cells is only marginal likely because the expression of PNPLA7, relative to that of its paralog PNPLA6, is repressed at a lower level due to its promoter methylation (see above) [51] and because PNPLA6 is compensatory upregulated following PNPLA7 knockdown (unpublished results) in this hepatoma cell line.