CXCL12 and acute myeloid leukemia: Moreover, CXCL12-CXCR4 contributes to AML chemoresistance, as it keeps leukemic cells in close contact with extracellular matrix components, like the integrin VLA-4 and the hyaluronate receptor CD44 [46], and with stromal cells that constitutively secrete growth-promoting and anti-apoptotic signals [48,49].