CXCL12 and acute lymphoblastic leukemia: T-ALL cells were demonstrated to be in a direct stable contact with BM stromal cells, namely vascular endothelium and osteoblasts, producing chemokine CXCL12, an important component for the T-ALL pathogenesis; CXCL12 acts via the CXCR4 receptor, which is expressed in leukemic cells (Pitt et al., 2015; Passaro et al., 2016).