Integrative Analysis of Copy Number and Gene Expression Data Suggests Novel Pathogenetic Mechanisms in Primary Myelofibrosis

Primary myelofibrosis (PMF) is a Myeloproliferative Neoplasm (MPN) characterized by megakaryocyte hyperplasia, progressive bone marrow fibrosis, extramedullary hematopoiesis and transformation to Acute Myeloid Leukemia (AML). A number of phenotypic driver (JAK2, CALR, MPL) and additional subclonal mutations have been described in PMF, pointing to a complex genomic landscape. To discover novel genomic lesions that can contribute to disease phenotype and/or development, we integrated gene expression and copy number (CN) signals and identified several genomic abnormalities leading to a concordant alteration in gene expression levels. In particular, copy number gain in the polyamine oxidase (PAOX) gene locus is accompanied by a coordinated transcriptional up-regulation in PMF patients. To assess the impact of PAOX deregulation on the survival of PMF and normal primary hematopoietic cells, PMF and normal donors cells were incubated with increasing doses of the PAOX inhibitor MDL-72,572. PAOX inhibition resulted in rapid cell death of PMF progenitor cells (5,7±0,9% of late apoptotic cells in NT sample vs 20,1±3,2% in 150μM treated-sample, p Moreover, our integrative analysis of gene expression and CN data pointed out the concomitant copy number loss and transcriptional down-regulation in PMF patients of the chromatin modifier HMGXB4 . Interestingly, silencing of HMGXB4 in CD34+ stem/progenitor cells induced megakaryocyte differentiation, as demonstrated by increased expression of CD41 (36±1,9% vs 26,1±2,9% at day 12, 52,5±4,9% vs 33±1% at day 14 of serum free liquid culture, p HMGXB4 in the hematopoietic system and suggest that genomic and transcriptional imbalances of HMGXB4 could contribute to the aberrant expansion of the megakaryocytic lineage that characterize PMF patients. In conclusion, our work sheds light on the influence of genomic abnormalities on gene expression regulation in PMF CD34+ cells and on their impact to features typical of PMF, such as a hyperplastic megakaryopoiesis and resistance to apoptosis, and therefore potentially contributing to the development of the myeloproliferative disease. Disclosures Vannucchi: Novartis: Other: Research Funding paid to institution (University of Florence), Research Funding; Shire: Speakers Bureau; Baxalta: Membership on an entity9s Board of Directors or advisory committees; Novartis: Membership on an entity9s Board of Directors or advisory committees, Speakers Bureau.