In summary, we show that the telomere length dynamics in CML cells including CD34+ cells is strictly related to the level of expression of BCR::ABL1, which stimulates an increase in expression of some shelterin genes, including TRF2, RAP1 and TPP1, as well as other telomere-associated proteins: DKC1, TNKS1, and TNKS2, promoting the shortening of telomeres regardless of telomerase activity. This evidence concerns the gene BCR and chronic myelogenous leukemia, BCR-ABL1 positive.