Nevertheless, our pivotal work did not answer the question about which kind of cells in CML would express BMI1; with the purpose to solve this clue, we designed the present study, whose aim was to find if the CD26+ cells, in the meanwhile identified as the true LSC, were the “reservoir” of this protein. This evidence concerns the gene BMI1 and chronic myelogenous leukemia, BCR-ABL1 positive.