We recently found that PNP is also present in human plasma (Giuliani et al., 2016) and that rat C6 glioma cells, astrocytes, and microglial cells (Giuliani et al., 2017; Peña-Altamira et al., 2018), can release PNP in the extracellular milieu. The gene discussed is PNP; the disease is central nervous system cancer.