On the contrary, CD26 (DPP4, a serine exopeptidase with a cleavage activity against diverse substrates and able to demolish SDF1 on the SDF1-CXCR4 axis contributing in this way to the release of the CML LSCs into the peripheral blood) [53,69] is aberrantly expressed by CML LSCs/progenitor cells and has no expression on normal HSC/progenitor cell population [70]. This evidence concerns the gene DPP4 and chronic myelogenous leukemia, BCR-ABL1 positive.