CRISPR/Cas9 technology abolishes the BCR/ABL1 oncogene in chronic myeloid leukemia and restores normal hematopoiesis

Chronic myeloid leukemia (CML) is a hematopoietic stem cell disease produced by a unique oncogenic event involving the constitutively active tyrosine kinase (TK) BCR/ABL1 . TK activity explains most features of CML, such as tumor development and maintenance. TK-inhibitory (TKI) drugs have changed its prognosis and natural history. Unfortunately, the ABL1 gene persists unaffected by TKIs, leukemic stem cells (LSCs) remains, resistant mutations arise and adverse effects may occur during treatment. To address this problem, we have designed a potential therapeutic alternative with CRISPR/Cas9 genome editing nucleases that target LSCs. The strategy was successfully developed in murine and human cell lines and finally was evaluated in primary LSCs isolated from CML transgenic mice and from CML patients. Mouse CML-LSCs edited were orthotopic transplanted in immunodeficient NSG niches where restored the normal hematopoiesis. Importantly, patient-derived xenografts with CD34+-LSCs edited, repopulated and restored the normal hematopoiesis in immunodeficient NSG niches. We show, for the first time, how CRISPR technology efficiently interrupts the BCR/ABL1 oncogene in murine and human LSCs to provide a significant therapeutic benefit. We propose human CML as a potential candidate for CRISPR therapy, providing proof-of-principle for genome editing in CML patients, and open new avenues for the application of this technique in other fusion genes. Key points CRISPR system destroys BCR/ABL oncogene and induces a therapeutic benefit in a CML mouse model and CML patient derived xenografts. ### Competing Interest Statement The authors have declared no competing interest.