The constitutively active tyrosine-kinase BCR/ABL1 oncogene plays a key role in human chronic myeloid leukemia development and disease maintenance, and determines most of the features of this leukemia. For this reason, tyrosine-kinase inhibitors are the first-line treatment, offering most patients a life expectancy like that of an equivalent healthy person. However, since the oncogene stays intact, lifelong oral medication is essential, even though this triggers adverse effects in many patients. Furthermore, leukemic stem cells remain quiescent and resistance is observed in approximately 25% of patients. Thus, new therapeutic alternatives are still needed. In this scenario, the interruption/deletion of the oncogenic sequence might be an effective therapeutic option. The emergence of CRISPR (clustered regularly interspaced short palindromic repeats) technology can offer a definitive treatment based on its capacity to induce a specific DNA double strand break. Besides, it has the advantage of providing complete and permanent oncogene knockout, while tyrosine kinase inhibitors (TKIs) only ensure that BCR-ABL1 oncoprotein is inactivated during treatment. CRISPR/Cas9 cuts DNA in a sequence-specific manner making it possible to turn oncogenes off in a way that was not previously feasible in humans. This review describes chronic myeloid leukemia (CML) disease and the main advances in the genome-editing field by which it may be treated in the future.

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, since ABL1 gene remains unaffected by TKIs, most patients should be treated with lifelong oral medication, resistant mutations arise and adverse effects occur during treatment in almost 25% of patients To address this problem, we have designed a potentially definitive therapeutic alternative with CRISPR/Cas9 genome editing nucleases that target leukemic stem cells (LSCs). CRISPR-edited LSCs lose their tumorigenic capacity and restore their own multipotency. The strategy was evaluated for the first time in a CML mouse model and in orthotopic assays with primary LSCs from CML patients. In Both systems, CRISPR-edited LSCs repopulated and restored the normal hematopoiesis in immunodeficient NSG niches providing a significant therapeutic benefit. We show for the first time how CRISPR technology permanently interrupts and avoids the BCR/ABL1 oncogene expression in human and mouse LSCs suggesting that human CML is an ideal candidate for CRISPR therapy, and providing proof-of-principle for genome editing in CML patients.

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The constitutively active tyrosine kinase BCR/ABL1 oncogene plays a key role in human chronic myeloid leukemia development and disease maintenance, and determines most of the features of this leukemia. For this reason, tyrosine kinase inhibitors are the first-line treatment, offering most patients a life expectancy like that of an equivalent healthy person. However, since the oncogene is not destroyed, lifelong oral medication is essential, even though this trigger adverse effects in many patients. Furthermore, leukemic stem cells remain quiescent and resistance is observed in approximately 25% of patients. Thus, new therapeutic alternatives are still needed. In this scenario, the emergence of CRISPR technology can offer a definitive treatment based on its capacity to disrupt coding sequences. This review describes CML disease and the main advances in the genome-editing field by which it may be treated in the future.

PurposeCentral choroidal dystrophies are retinal diseases characterized by progressive choriocapillaris atrophy and retinal degeneration that are usually associated with a single mutation in the PRPH2 gene. Thus, the purpose of this work was to generate a mouse model with the same p.Arg195Leu mutation described in diagnosed human patients.MethodsPrph2KI/WT and Prph2KI/KI mice have been designed and generated using the CRISPR system to introduce the Arg195Leu mutation. The retinal function was analyzed by electroretinography (ERG) and optomotor test. The structural integrity of the retinas was evaluated using optical coherence tomography and immunohistochemistry.ResultsGenetic sequencing confirmed that both Prph2KI/WT and Prph2KI/KI mice presented the same codon mutation and degeneration pattern found in humans suffering from this dystrophy. A progressive loss of retinal function was found from 3 months of age, with significantly reduced mice visual acuity, measured by optomotor test. At 6 months of age, decreased a‐ and b‐wave amplitudes of the ERG responses were observed. Moreover, morphological analysis of the retinas correlated with functional findings, showing a decreased number of photoreceptor rows and retinal thickness, also presenting an increased inflammation with activation of microglia and Müller cellsConclusionsThe new Prph2KI/WT and Prph2KI/KI mouse models show a similar degeneration pattern to human disease and may facilitate the study of the pathophysiological process, also displaying their potential to be a model for evaluation of different therapeutic strategies.SupportMinisterio de Ciencia e Innovación (FEDER‐ PID2019‐106230RB‐I00). Ministerio de Universidades (FPU16/04114, FPU18/02964). Instituto Carlos III (RETICS‐FEDER RD16/0008/0016). Retina Asturias/Cantabria. FARPE‐FUNDALUCE. Generalitat Valenciana (IDIFEDER/2017/064, ACIF/2020/203). Es Retina Asturias (2019/00286/001).