Among the chronic Philadelphia-negative myeloproliferative neoplasms (MPNs), myelofibrosis (MF) stands out as the most aggressive disease. It is characterized by extensive deposition of extracellular matrix fibers in the bone marrow (BM), leading to destruction of the microenvironment. Like other MPNs, MF originates from somatic mutations acquired from hematopoietic stem/progenitor cells (HSPCs). Mutations in genes such as JAK2, MPL, and CALR have been identified as driver events responsible for the onset of the myeloproliferative phenotype.
Hypothesis
Preliminary results obtained in our laboratory revealed that MF HSPCs express specific surface markers that distinguish them from HSPCs of healthy donors. Recent studies have shown that NSG-SGM3 (NSGS) mice enable efficient engraftment of MF CD34+ HSPCs, replicating the myeloproliferative phenotype of human disease, including clonal complexity and development of bone marrow fibrosis. This makes NSGS mice a promising platform to study MF stem cells and to evaluate novel therapeutic strategies, such as targeting osteopontin (OPN), which we have identified as a secreted protein with a profibrotic role in MF.
Objectives
To identify and characterize MF HSPCs responsible for neoplastic cloning.
Establish MF patient-derived xenografts (PDX) to confirm that specific subpopulations of MF HSPCs propagate disease in vivo.
Evaluate therapeutic strategies targeting neoplastic stem cells and fibrosis development.
Experimental Plan
Characterization of HSPCs of MF: Based on preliminary results, we will isolate subpopulations of HSPCs based on the expression of specific surface markers such as CD133, CD244 and CD9. Their expression will be correlated with disease-specific gene mutations using a multi-omics approach.
Molecular Analysis: We will define the molecular pathways that support the survival and expansion of neoplastic HSPCs by analyzing their transcriptome and evaluating their function in vitro.
In Vivo Studies: We will transplant identified subpopulations of HSPCs into NSGS mice to test their ability to replicate MF, including bone marrow fibrosis.
Therapeutic Testing: We will use the PDX model to:
Evaluate novel immunotherapies targeting MF stem cells.
Study the mechanisms responsible for the development of fibrosis.
Test antifibrotic molecules that inhibit OPN production or other profibrotic pathways.
Expected Results.
This project will make it possible to identify MF stem cells that can be distinguished from their normal counterparts based on the expression of surface markers. We expect to be able to design alternative therapeutic approaches targeting MF stem cells and fibrosis, the efficacy of which will be evaluated using the PDX mouse model of MF.
Impact on Cancer
To date, approved targeted therapies, including JAK/STAT inhibitors, have been shown to have only a limited effect in reducing disease burden and bone marrow fibrosis in patients. Therefore, there is an urgent need to develop more effective therapeutic approaches. Better characterization of MF stem cells is critical to identify new therapeutic targets that may enable eradication of the neoplastic clone and treatment of bone marrow fibrosis in patients.