BCR and chronic myelogenous leukemia, BCR-ABL1 positive: However, CXCL12 levels were similar in patients with CML‐BC (blastic crisis) and control samples.33 Using mice models with the BCR‐ABL transgene, it was shown that the exosome‐derived miR‐126 secreted by CML cells reduced the expression of CXCL12 in bone marrow endothelial cells.34 The decreased expression of CXCL12 in bone marrow endothelial cells may induce the outflow of CML cells into the bloodstream due to the suppression of the CXCL12/CXCR4 axis signal, followed by the induction of splenomegaly.