Mutant IDH1 impairs growth in KMT2A-r cells. (A) Western blot analysis of global H3K79me2 in patient AML samples with or without mutations in IDH1/2. Previously banked bone marrow samples from patients with AML were thawed and directly analyzed by western blotting. Characterization of patient samples can be found in supplemental Table 1. Western blot analysis of 3T3 cells transduced with IDH1^R132H or control for IDH1^R132H and total IDH1 (mutant + WT) (B) and H3K79me2 (C). 3T3 cells were sorted 4 days after retroviral transduction with IDH1^R132 and were subjected to western blotting. Western blot analysis of murine KMT2A-MLLT3 AML cells transduced with IDH1^R132H or control for IDH1^R132H and total IDH1 (mutant + WT) (D) and for H3K79me2 (E). Fully transformed murine KMT2A-MLLT3 AML cells were isolated from mice and transduced with IDH1^R132-GFP or GFP-only control vector. Cells were sorted 4 days after retroviral transduction and subjected to western blotting. (F) Growth of IDH1^R132-transduced sorted EOL-1 (human KMT2A^PTD cell line) and murine KMT2A-MLLT3 AML cells as a percentage of empty vector control 12 days after transduction. Error bars represent standard deviation (SD). (G-H) Flow data from competition assay. EOL-1 cells (G) or murine KMT2A-MLLT3 AML cells (H) were transduced with IDH1^R132 or the control vector, sorted, mixed 1:1, and plated together. The coculture was analyzed by flow cytometry every 3 days. Error bars represent SD. *P < .01, **P < .001; Student t test.