(A) CD34+ HDR HSPCs were treated with JAK inhibitors or DMSO control for 72 hours, and cell numbers were determined using CountBright beads and flow cytometry. n = 3–5 CB. Least sum-of-squares F test. (B) Drug sensitivity to JAK inhibitors in RUNX1wt and RUNX1mut primary AML samples from BeatAML. n = 87–406 RUNX1wt, n = 11–53 RUNX1mut. Unpaired t test. (C) RUNX1mut (SU032, SU371, dark red) and RUNX1wt (SU681, SU770, black) were treated with JAK inhibitors or DMSO control for 72 hours, and cell numbers were determined using CountBright beads and flow cytometry. n = 2 technical replicates. Least sum-of-squares F test.