CXCR4 and chronic myelogenous leukemia, BCR-ABL1 positive: SDF-1a/CXCR4 interactions between CML cells and MSCs protect CML cells from imatinib-induced cell death by reducing activation of caspase-3 and promoting the expression of Bcl-XL, an important anti-apoptotic protein inhibited by imatinib (Vianello et al., 2010).