Furthermore, the expression of PRPS1, PRPS2, PRPSAP1 (PAP39) and PRPSAP2 (PAP41) genes in U87 glioma cells is not inhibited by ERN1 (EC 2.7.11, endoribonuclease activity of endoplasmic reticulum to nuclei-1). This evidence concerns the gene ERN1 and central nervous system cancer.