Targeting the cellular origin of myelofibrosis

• Applicant: Professor Dr. Rafael Kramann, since 9/2016
• Subject Area: Hematology, Oncology ; Pathology
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 314914853

Myelofibrosis is one of the three classic Philadelphia-chromosome-negative myeloproliferative neoplasms (MPNs), the other two being polycythemia vera and essential thrombocythemia. Of these entities myelofibrosis has the most aggressive course. Despite the enormous progress in the elucidation of potential molecular targets and increased understanding of the myeloproliferative neoplasms, the cellular targets of myelofibrosis remain still obscure and are far less understood than in solid organ fibrosis. Our recent identification of perivascular Gli1+ progenitor cells as a major cellular origin of organ fibrosis and as a relevant therapeutic target to prevent solid organ dysfunction, provides significant potential to identify the origin of fibrosis-driving cells in myelofibrosis. In preliminary studies in Thrombopoietin-overexpression induced myelofibrosis, we provided the first in vivo functional evidence that Gli1+ cells are fibrosis-driving cells in myelofibrosis and that their ablation rescues myelofibrotic transformation without detrimental effects on hematopoiesis. These results raise the possibility that Gli1+ precursor cells are the long-sought cellular target in myelofibrosis. In the current proposal we aim to identify the cellular source of myelofibrosis to elucidate targetable mechanisms of myelofibrotic transformation. We will apply (a) novel and established murine models for myelofibrosis, (b) perform genetic fate tracing and genetic cell ablation, (c) modify cells by genome engineering using the CRISPR-Cas9 technology and (d) test commercially available small compounds with the ultimate goal to determine the fate and functional role of resident Gli1+ progenitor cells in myelofibrotic transformation. We hypothesize that Hedgehog-Gli signaling in myelofibrosis is a promising target and we will specifically answer the question if Gli proteins can be activated independent of canonical Hh signaling, which will provide novel insights into targeting strategies of Hh signaling in myelofibrosis. In an unbiased approach, we will further leverage the unique tool of Gli1+ cells as fibrosing-causing precursors to specifically isolate them from bone marrow and to characterize these cells in health and upon fibrotic transformation using translational ribosome affinity purification (TRAP) followed by RNA sequencing and an iTRAQ proteomic approach that we have established on a small number of primary cells. Top hits will be screened for novelty and drugability and moved forward into established multistep in vitro and in vivo validation processes. In parallel, we will extensively characterize Gli1+ cells in human bone marrows to translate our findings into human disease and potential clinical applications.Identifying the cellular origin of myelofibrosis driving myofibroblasts will be a huge step towards a better understanding of disease and the development of novel targeted therapeutics.

• DFG Programme: Research Grants
• Ehemalige Antragstellerin: Professorin Dr. Rebekka Schneider-Kramann, until 8/2016