CXCR4 and acute lymphoblastic leukemia: Evidence indicates that the CXCL12/CXCR4 signaling axis plays a role in cancer biology, in solid tumors as well as in hematological malignancies such as T-ALL, where the CXCL12/CXCR4 signaling regulates the maintenance and progression of leukemia [18,26,27,28,29].