P2RX7 and neoplasm: Extracellular ATP is present at concentrations in the low nanomolar range in healthy tissue but can increase dramatically upon tissue damage, inflammation or during tumor development to the tens to hundreds of micromolar range and reach the high activation threshold of 0.3 to 0.5mM for P2X7 (Di Virgilio, 2015; Morciano et al., 2017; Di Virgilio et al., 2018b).