CXCR4 and leukemia: The concept whereby inhibition of the CXCL12‐CXCR4 axis by RGS1 contributes to leukemogenesis might appear to contradict recent findings showing that leukemia cells use the CXCL12‐CXCR4 axis to access and reside in a bone marrow microenvironment that is expected to favor their growth and survival.28