P2RX7 and hepatocellular carcinoma: While further studies are required to examine the potential contribution of P2X2 and P2X6 receptors, it is clear from the present study that that the P2X4 and P2X7 receptors are unlikely to have a significant role in mediating ATP-induced Ca2+ responses in Huh-7 cells, thus differing from rat HCC cells [39].