PTPRZ1 and neoplasm: To determine the expression of PTPRZ1 in GSCs, we used two independent GEO microarray data sets (GDS3885 and GSE54791) and found that PTPRZ1 was one of the 83 genes significantly upregulated in GSCs (average fold changes >3.0) relative to the matched non-tumour stem cells (NSTCs) (Fig. 3b and Supplementary Table 2).