PTGDS and glioblastoma: Regarding the genes included in the twiner signature, the following 8 genes were always selected: APOD, CDR1, EGFR, HTRA1, IGFBP2, MGLL, PTGDS, and SEC61G, some previously selected by Model II, also classifying GBM cells into neoplastic (from the tumor periphery) and normal astrocytes.