IDH1 and glioblastoma: Our TCGA analysis of GBM patients revealed that the groups with elevated expression of PHGDH, PSAT1, SHMT1, and SHMT2 exhibited higher expression levels of IDH2. Notably, only high PSAT1 and SHMT1 expression were associated with elevated levels of IDH1 compared to patients with low PSAT1 and SHMT1 expression (Fig. 4).