P2X7, an important receptor for ATP signalling, is overexpressed in many tumours and has been established as a mediator of inflammatory cytokine release into circulation e.g. IL-1β and TNF-α [147], as well as proteases e.g. matrix metalloproteinase-9 (MMP-9) [148] and cathepsins [149] that could contribute to tumour progression. This evidence concerns the gene CTSS and neoplasm.