Title: Early detection of platelet biased HSCs in myelofibrosis and clonal haematopoiesis
Funder: Cancer Research UK

Abstract: Background: Accumulating evidence supports that many long-term haematopoietic stem cells (HSCs) produce cells exclusively of the platelet lineage. We hypothesise that specific detection of platelet-biased HSCs and/or their progeny will have clinical utility for early detection of clonal haematopoiesis and relapse. Myelofibrosis (MF) is a poor prognosis myeloproliferative neoplasm (MPN) in which clonal haematopoietic stem/progenitor cells produce a massive excess of aberrant megakaryocytes that drive bone marrow (BM) fibrosis. Allogeneic HSC transplantation (AHSCT) remains the only curative option for patients with MF. However, relapse post-transplant remains a major problem and current methods of post-AHSCT monitoring do not detect platelet-biased HSC clones. Clonal haematopoiesis is common in aged populations, and increases the risk of development of haematopoietic malignancy. As platelet-biased HSC clones also increase in frequency with age, we anticipate that screening for clonal haematopoiesis in platelet lineage cells will increase the sensitivity for early detection of impending haematopoietic malignancy. Aims: 1. To monitor myelofibrosis patients post-AHSCT for presence of platelet-biased HSC clones to allow early detection of relapse 2. To screen normal populations for early detection of platelet-restricted clonal haematopoiesis Methods: Aim 1a: Using state-of-the-art stem cell and molecular biology techniques, including single cell analysis, this project will focus on the characterisation of haematopoietic stem and progenitor cells (HSPCs) in MF patients post-AHSCT in order to identify the cells responsible for driving subsequent relapse. We will analyse serial samples in a cohort of 40 MF patients pre- and post-transplant. Aim 1b: In parallel to single-cell HSPC analysis, we will carry out serial chimerism and mutational analysis of all blood cell lineages, particular cells of the platelet lineage, to monitor for presence of platelet restricted clones in MF patients post-AHSCT. Aim 2: We will screen a cohort of normal donors for the presence of platelet-restricted clonal haematopoiesis i.e. presence of JAK2V617F mutation in cDNA from platelets, but not in other blood cell lineages. How the results of this research will be used: Our expectation is that there will be a tangible impact of this work on patient outcomes through better approaches to monitor MF patients post-AHSCT and to detect clonal haematopoiesis. This will allow early intervention and might also help to identify novel therapeutic candidate targets. More broadly, this work will also provide proof of principle of the clinical utility of single-cell genomic analysis. Dissemination will be through publications, presentations at international meetings and engagement with patient and carer organisations.

Lay abstract: Background: Accumulating evidence supports that many long-term haematopoietic stem cells (HSCs) produce cells exclusively of the platelet lineage. We hypothesise that specific detection of platelet-biased HSCs and/or their progeny will have clinical utility for early detection of clonal haematopoiesis and relapse. Myelofibrosis (MF) is a poor prognosis myeloproliferative neoplasm (MPN) in which clonal haematopoietic stem/progenitor cells produce a massive excess of aberrant megakaryocytes that drive bone marrow (BM) fibrosis. Allogeneic HSC transplantation (AHSCT) remains the only curative option for patients with MF. However, relapse post-transplant remains a major problem and current methods of post-AHSCT monitoring do not detect platelet-biased HSC clones. Clonal haematopoiesis is common in aged populations, and increases the risk of development of haematopoietic malignancy. As platelet-biased HSC clones also increase in frequency with age, we anticipate that screening for clonal haematopoiesis in platelet lineage cells will increase the sensitivity for early detection of impending haematopoietic malignancy. Aims: 1. To monitor myelofibrosis patients post-AHSCT for presence of platelet-biased HSC clones to allow early detection of relapse 2. To screen normal populations for early detection of platelet-restricted clonal haematopoiesis Methods: Aim 1a: Using state-of-the-art stem cell and molecular biology techniques, including single cell analysis, this project will focus on the characterisation of haematopoietic stem and progenitor cells (HSPCs) in MF patients post-AHSCT in order to identify the cells responsible for driving subsequent relapse. We will analyse serial samples in a cohort of 40 MF patients pre- and post-transplant. Aim 1b: In parallel to single-cell HSPC analysis, we will carry out serial chimerism and mutational analysis of all blood cell lineages, particular cells of the platelet lineage, to monitor for presence of platelet restricted clones in MF patients post-AHSCT. Aim 2: We will screen a cohort of normal donors for the presence of platelet-restricted clonal haematopoiesis i.e. presence of JAK2V617F mutation in cDNA from platelets, but not in other blood cell lineages. How the results of this research will be used: Our expectation is that there will be a tangible impact of this work on patient outcomes through better approaches to monitor MF patients post-AHSCT and to detect clonal haematopoiesis. This will allow early intervention and might also help to identify novel therapeutic candidate targets. More broadly, this work will also provide proof of principle of the clinical utility of single-cell genomic analysis. Dissemination will be through publications, presentations at international meetings and engagement with patient and carer organisations.

Research activity codes: 4.2 EVALUATION OF MARKERS AND TECHNOLOGIES
Health categories: CANCER AND NEOPLASMS