P2RX4 and hepatocellular carcinoma: There is evidence to indicate mRNA and/or protein expression of the P2Y1 and P2Y2 receptors in primary and immortalized human normal hepatocytes, primary human HCC cells and immortal human HCC cells (e.g., Huh-7, HepG2 and BEL-7404) [37–39], and the P2X4 and P2X7 receptors in HepG2 cells, rat and mouse hepatocytes and rat HCC cells [38].