CRISPR-Cas9-induced t(11;19)/MLL-ENL translocations initiate leukemia in human hematopoietic progenitor cells in vivo

Abstract

Chromosomal translocations that generate oncogenic fusion proteins are causative for most pediatric leukemias and frequently affect the MLL/KMT2A gene. In vivo modeling of bona fide chromosomal translocations in human hematopoietic stem and progenitor cells is challenging but essential to determine their actual leukemogenic potential. We therefore developed an advanced lentiviral CRISPR-Cas9 vector that efficiently transduced human CD34+ hematopoietic stem and progenitor cells and induced the t(11;19)/MLL-ENL translocation. Leveraging this system, we could demonstrate that hematopoietic stem and progenitor cells harboring the translocation showed only a transient clonal growth advantage in vitro. In contrast, t(11;19)/MLL-ENL-harboring CD34+ hematopoietic stem and progenitor cells not only showed long-term engraftment in primary immunodeficient recipients, but t(11;19)/MLL-ENL also served as a first hit to initiate a monocytic leukemia-like disease. Interestingly, secondary recipients developed acute lymphoblastic leukemia with incomplete penetrance. These findings indicate that environmental cues not only contribute to the disease phenotype, but also to t(11;19)/MLL-ENL-mediated oncogenic transformation itself. Thus, by investigating the true chromosomal t(11;19) rearrangement in its natural genomic context, our study emphasizes the importance of environmental cues for the pathogenesis of pediatric leukemias, opening an avenue for novel treatment options.

Modeling mixed-lineage-rearranged leukemia initiation in CD34 + cells: a “CRISPR” solution

“…Based on these findings, the authors conclude that "environmental cues not only contribute to the disease phenotype, but also to t(11;19)/MLL-ENL-mediated oncogenic transformation". 1 This result resembles the effect of chemotherapy in patients, but it will need to be confirmed in future studies.…”

“…The present article by Reimer et al 1 illustrates how the use of more accurate models generated by genome engineering techniques in human CD34 + HPSCs can transform the field of basic leukemia biology. A deeper knowledge of the CRISPR approach and the development of new applications should open new horizons for the study of the molecular and cellular processes of cancer, and will make it easier to reproduce the complex cancer genome and epigenome, allowing a more rigorous molecular analysis of the molecular mechanisms involved in tumor progression and the identification of oncogenes and tumor suppressor genes.…”

“…E-mail: rtorres@carrerasresearch.org or pmenendez@carrerasresearch.org doi: 10.3324/haematol.2017.173740 I n this issue of haematologica, Reimer et al 1 present an improved strategy based on genome engineering, viral vector transduction, and the use of CD34 + human hematopoietic stem and progenitor cells (HPSCs) to recreate a human leukemic chromosomal rearrangement, t(11;19)/MLL-ENL, in its natural genomic environment. This model provides new clues as to the complex molecular mechanisms of mixed-lineage-rearranged (MLLr) leukemia and opens up new avenues for the genomic reconstruction to study leukemia initiation and evolution.…”

“…In the present article, Reimer et al 1 combine the undemanding aspects of lentiviral generation and delivery with the advantages of chromosomal translocation generation by the CRISPR system. The authors engineered an advanced lentiviral CRISPR/Cas9 vector for efficient transduction of human CD34 + HPSCs.…”

MLL leukemia induction by t(9;11) chromosomal translocation in human hematopoietic stem cells using genome editing

“…[11][12][13][14] Despite the increasing feasibility of using novel genome editing tools to generate alterations in primary human HSPCs mimicking the nature of patient disease, it remains difficult to achieve sufficient numbers due to both low efficiency as well as the lack of marker proteins that allow for selective recognition and analysis of the translocated cells.…”