While studying the high-affinity GTPase activity of G-proteins in membrane from primary human skin fibroblasts, rat B103 neuroblastoma cells and mouse Neuro-2a neuroblastoma cells, Pinto et al. [146] unexpectedly found that the membrane low-affinity nucleoside 5-triphosphatase activity (NTPase) was decreased up to 7-fold in HPRT deficiency. This evidence concerns the gene HPRT1 and neuroblastoma.