P2RX4 and neoplasm: Several types of P2 receptors were shown to be involved in regulating the proliferation of numerous tumor cells, including P2X3, P2X4, P2X5, P2X7, P2Y1, P2Y2, P2Y4 P2Y11, and P2Y12 [17,18,19,20,21,22,23,24].