CXCR4 and acute myeloid leukemia: Consistent with this theory, a recent analysis by Bjorklund et al. showed that high expression levels of the BM homing chemokine receptor CXCR4 on the infused NK cells was associated with increased probability of objective response in patients with relapsed/refractory acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS) (5).