CXCR4 and acute lymphoblastic leukemia: We and others have previously shown that anti-leukemic agents can modulate CXCR4 expression in ALL,[10,25] AML,[10] chronic lymphocytic leukemia,[26] and chronic myelogenous leukemia.[27] Therefore, initial levels and changes in levels of CXCR4 in leukemia cells may affect the protection conferred by bone marrow niches.