1. Academic Validation
  2. Human gene-engineered calreticulin mutant stem cells recapitulate MPN hallmarks and identify targetable vulnerabilities

Human gene-engineered calreticulin mutant stem cells recapitulate MPN hallmarks and identify targetable vulnerabilities

  • Leukemia. 2023 Feb 22. doi: 10.1038/s41375-023-01848-6.
Johannes Foßelteder 1 Gabriel Pabst 1 2 3 Tommaso Sconocchia 1 Angelika Schlacher 1 Lisa Auinger 1 Karl Kashofer 4 Christine Beham-Schmid 4 Slave Trajanoski 5 Claudia Waskow 6 7 Wolfgang Schöll 8 Heinz Sill 1 Armin Zebisch 1 9 Albert Wölfler 1 Daniel Thomas 10 11 Andreas Reinisch 12 13
Affiliations

Affiliations

  • 1 Department of Internal Medicine, Division of Hematology, Medical University of Graz, Graz, Austria.
  • 2 Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria.
  • 3 Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna BioCenter (VBC), Vienna, Austria.
  • 4 Diagnostic & Research Institute of Pathology, Medical University of Graz, Graz, Austria.
  • 5 Core Facility Computational Bioanalytics, Medical University of Graz, Graz, Austria.
  • 6 Leibniz Institute on Aging, Fritz Lipmann Institute, Jena, Germany.
  • 7 Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich-Schiller-University, Jena, Germany.
  • 8 Department of Obstetrics and Gynecology, Medical University of Graz, Graz, Austria.
  • 9 Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Division of Pharmacology, Medical University of Graz, Graz, Austria.
  • 10 Cancer Program, Precision Medicine Theme, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia.
  • 11 Adelaide Medical School, The University of Adelaide, Adelaide, Australia.
  • 12 Department of Internal Medicine, Division of Hematology, Medical University of Graz, Graz, Austria. a.reinisch@medunigraz.at.
  • 13 Department of Blood Group Serology and Transfusion Medicine, Medical University of Graz, Graz, Austria. a.reinisch@medunigraz.at.
Abstract

Calreticulin (CALR) mutations present the main oncogenic drivers in JAK2 wildtype (WT) myeloproliferative neoplasms (MPN), including essential thrombocythemia and myelofibrosis, where mutant (MUT) CALR is increasingly recognized as a suitable mutation-specific drug target. However, our current understanding of its mechanism-of-action is derived from mouse models or immortalized cell lines, where cross-species differences, ectopic over-expression and lack of disease penetrance are hampering translational research. Here, we describe the first human gene-engineered model of CALR MUT MPN using a CRISPR/Cas9 and adeno-associated viral vector-mediated knock-in strategy in primary human hematopoietic stem and progenitor cells (HSPCs) to establish a reproducible and trackable phenotype in vitro and in xenografted mice. Our humanized model recapitulates many disease hallmarks: thrombopoietin-independent megakaryopoiesis, myeloid-lineage skewing, splenomegaly, bone marrow fibrosis, and expansion of megakaryocyte-primed CD41+ progenitors. Strikingly, introduction of CALR mutations enforced early reprogramming of human HSPCs and the induction of an endoplasmic reticulum stress response. The observed compensatory upregulation of chaperones revealed novel mutation-specific vulnerabilities with preferential sensitivity of CALR mutant cells to inhibition of the BiP chaperone and the Proteasome. Overall, our humanized model improves purely murine models and provides a readily usable basis for testing of novel therapeutic strategies in a human setting.

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