CRISPR/Cas9-mediated gene editing. A promising strategy in hematological disorders

The clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system has revolutionized the gene editing field, making it possible to interrupt, insert or replace a sequence of interest with high precision in the human genome. Its easy design and wide applicability open up a variety of therapeutic alternatives for the treatment of genetic diseases. Indeed, very promising approaches for the correction of hematological disorders have been developed in the recent years, based on the self-renewal and multipotent differentiation properties of hematopoietic stem and progenitor cells, which make this cell subset the ideal target for gene therapy purposes. This technology has been applied in different congenital blood disorders, such as primary immunodeficiencies, X-linked severe combined immunodeficiency, X-linked chronic granulomatous disease or Wiskott-Aldrich syndrome, and inherited bone marrow failure syndromes, such as Fanconi anemia, congenital amegakaryocytic thrombocytopenia or severe congenital neutropenia. Furthermore, CRISPR/Cas9-based gene editing has been implemented successfully as a novel therapy for cancer immunotherapy, by the development of promising strategies such as the use of oncolytic viruses or adoptive cellular therapy to the chimeric antigen receptor-T-cell therapy. Therefore, considering the variety of genes and mutations affected, we can take advantage of the different DNA repair mechanisms by CRISPR/Cas9 in different manners, from homology-directed repair to non-homologous-end-joining to the latest emerging technologies such as base and prime editing. Although the delivery systems into hematopoietic stem and progenitor cells are still the bottleneck of this technology, some of the advances in genome editing shown in this review have already reached a clinical stage and show very promising preliminary results.