CD34 and acute myeloid leukemia: To dissect whether the activity of THZ1 against the GPR56+ compartment was caused by CDK7 or CDK12/13 inhibition, we treated the GPR56+ AML cell line HEL (Fig 5G, Appendix Fig 5E) and healthy CB CD34+ cells (Appendix Fig 5F) with specific CDK7i (YKL‐5‐124) and CDK12/13i (THZ531) (Kwiatkowski et al, 2014; Zeng et al, 2018; Olson et al, 2019).