GPT and glioblastoma: Regarding the 28 missense alterations (Fig. 3c), 19 were detected as ALT + (8 of which showed ATRX loss by IHC and were further classified as LOF), while 9 were classified as TA + and preserved ATRX expression by IHC (8 GBM and 1 OD), considered likely secondary mutations (Supplementary Table 1).