P2RX7 and neoplasm: P2X7 is a cytotoxic receptor that, upon short-term activation by ATP, opens a non-selective cation channel that promotes Ca2+ influx, while chronically high concentrations of P2X7 open to form an osmotic macropore, which is detrimental to tumor cells, but it can also express a non-macroporous functional P2X7 heterodimer (nfP2X7) that escapes this injury (5, 38).