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

Area of Science:

• Hematology
• Oncology
• Molecular Biology

Background:

• Calreticulin (CALR) mutations are key drivers in JAK2 wildtype myeloproliferative neoplasms (MPN).
• Current models using cell lines or mice have limitations in translational research due to cross-species differences and ectopic expression.
• Mutant CALR is a recognized drug target, but understanding its mechanism requires better models.

Purpose of the Study:

• To create the first human gene-engineered model of CALR mutation-positive MPN.
• To establish a reproducible and trackable in vitro and in vivo model using human cells.
• To identify novel therapeutic vulnerabilities associated with CALR mutations.

Main Methods:

• CRISPR/Cas9 and adeno-associated viral vector-mediated knock-in in primary human hematopoietic stem and progenitor cells (HSPCs).
• Establishment of a humanized model in vitro and in xenografted mice.
• Analysis of cellular reprogramming, endoplasmic reticulum stress response, and chaperone expression.

Main Results:

• The humanized model recapitulated key MPN hallmarks: thrombopoietin-independent megakaryopoiesis, myeloid skewing, splenomegaly, and bone marrow fibrosis.
• CALR mutations induced early reprogramming of human HSPCs and endoplasmic reticulum stress.
• Compensatory chaperone upregulation identified mutation-specific vulnerabilities.

Conclusions:

• This humanized model overcomes limitations of murine models for studying CALR-mutant MPN.
• The model demonstrates that CALR mutations confer sensitivity to BiP chaperone and proteasome inhibition.
• It provides a valuable platform for testing new therapeutic strategies in a human context.