CXCR4 and acute lymphoblastic leukemia: CXCL12, which binds to CXCR4 expressed in hematopoietic cells, has been also suggested as a crucial regulatory axis in B cell malignancies, like childhood acute lymphoblastic leukemia (ALL) (Greenbaum et al., 2013; Pérez-Saldivar et al., 2011; Sugiyama et al., 2006; Tokoyoda et al., 2004; Enciso et al., 2016; Balandrán et al., 2017).