Overall, these data corroborate those already found in rat glioma C6 cells and in rat astrocytes and microglial cells (Giuliani et al., 2017; Peña-Altamira et al., 2018) and further support the existence of a constitutive release of PNP from cells that, in these experiments, was unaffected by GUO treatment. The gene discussed is PNP; the disease is central nervous system cancer.