CXCL12 and acute lymphoblastic leukemia: At higher concentrations, pretreatment with GPR15LG reduced CXCL12-induced Ca++ signaling in the BCR-ABL ALL cell line (Fig. 4d), and attenuated CXCL12-mediated CXCR4 C-terminal modification in primary CD4+ T cells (Fig. 4e).