Targeting HMGA1-Mediated Progression and Immune Evasion in Myeloproliferative Diseases

我建议阐明高迁移率组A1 （HMGA1）染色质调节因子介导的机制

I propose to elucidate mechanisms mediated by High Mobility Group A1 (HMGA1) chromatin regulators in disease progression in myeloproliferative neoplasms (MPN). MPN are blood diseases caused by mutations in hematopoietic stem and progenitor cells (HSPC) which lead to clonal expansion. Individuals with MPN are at increased risk for transformation to bone marrow fibrosis (myelofibrosis or MF) and leukemia, both of which are associated with poor clinical outcomes. However, mechanisms underlying progression remain poorly understood. The most common genetic lesion causing MPN is a mutation in Janus Kinase 2 (JAK2), the obligate tyrosine kinase of hematopoietic growth factor receptors. This mutation (denoted JAK2V617F) causes enhanced phosphorylation of the Signal Transducer and Activator of Transcription (STAT3), resulting in uncontrolled production of blood cells. Importantly, inhibiting JAK/STAT signaling improves symptoms but does not prevent progression. Here, I focus on HMGA1 as a key mediator of JAK/STAT signaling in MPN progression. Our scientific premise that HMGA1 fosters progression in MPN is based on the following compelling preliminary results: 1) HMGA1 is a chromatin regulator that “opens” chromatin to induce STAT3 and other genes involved in clonal expansion in human blood cell progenitors. 2) Blocking JAK/STAT signaling in MPN cells decreases HMGA1, suggesting that JAK/STAT signals induce HMGA1, and HMGA1 feeds forward to amplify STAT3 signals. 3) Hmga1 overexpression causes clonal expansion in mouse blood cell progenitors, which evolves to leukemia with aging. 4) Hmga1 deficiency mitigates progression in mice with JAK2V617F MPN. 5) In human JAK2V617F mutant MPN cells, HMGA1 is required for proliferation, clonogenicity, and leukemia engraftment in mice. 6) HMGA1 increases in human HSPC with MPN progression to MF or leukemia. 7) HMGA1 regulates gene networks involved in cell cycle progression and immune evasion in MPN based on RNA sequencing results. 8) HMGA1 is also linked to gene networks associated with abnormal growth and immune evasion in solid tumors and other hematologic cancers. Together, these intriguing results support the following hypotheses: 1) HMGA1 cooperates with STAT3 to foster clonal expansion, immune evasion, and MPN progression, 2) HMGA1 drives progression through gene networks involved in proliferation and immune function, 3) Targeting HMGA1 and STAT3 will prevent clonal expansion, immune evasion, and MPN progression. Aims/Approach: To test this, we propose the following Specific Aims: 1) To determine whether HMGA1 and STAT3 generate a feed-forward loop to promote MPN progression, 2) To determine how HMGA1 alters the immune response in MPN, 3) To begin to test the therapeutic efficacy of targeting both HMGA1 and STAT3 to prevent aberrant clonal expansion, immune evasion, and MPN progression. Impact: We expect to elucidate mechanisms inducing HMGA1 and downstream pathways in MPN. This work should also reveal novel approaches to treat, or even prevent, progression in patients with MPN.