CD34 and acute myeloid leukemia: Sorf et al., demonstrated that ribociclib, a C4C/6 inhibitor approved for the treatment of locally advanced/metastatic breast cancer, inhibits ABCB1- and ABCG2-mediated daunorubicin and mitoxantrone efflux in AML cell lines at IC50 ranging between 1,4–3 μM, suggesting that combination therapy can revert MDR, especially in CD34+/FLT3-WT cases [148].