G6PD (A, C, E, G) and IDH1 activity (B, D, F, H) staining of IDH1^WT (A, B, E, F) and IDH1^MT (C, D, G, H) primary AML cells (A-D) and glioblastoma (E-H) cryostat sections. The amount of blue color directly reflects enzyme activity (production of NADPH).