PROJECT SUMMARY/ABSTRACT Background: Allogeneic hematopoietic cell transplant (allo-HCT) remains the only curative therapy for many aggressive malignancies and is increasingly used for non-malignant disorders. Success is limited by 1) relapse due to insufficient graft-vs-tumor (GVT) activity and 2) graft-vs-host disease (GVHD). Current GVHD therapies predispose to infection and relapse. Understanding the mechanisms that optimize GVT activity and mitigate GVHD remains a critical unmet need. Donor T-cells are essential to the allogeneic immune response. De novo DNA methylation by DNMT3a allows activated T-cells to acquire patterns of gene expression that define alloreactivity. Human donor DNMT3a mutations result in decreased relapse, increased GVHD, and improved survival in HCT recipients. Based on a large body of preliminary data, both GVHD and GVT activity significantly depend upon DNA methylation, the role of which is largely unknown in the HCT context. I hypothesize that targeting epigenetically controlled pathways can skew allogeneic immunity away from host and towards tumor. Design: Mice with cell-lineage specific DNMT3a deletion will be used as donors in well-established, clinically relevant, murine models of HCT. Following HCT, donor cells will be isolated from recipient mice and undergo whole genome bisulfite sequencing (WGBS) and RNA sequencing (RNAseq) in parallel. This novel approach, proven to be feasible and successful in my preliminary work, produces a comprehensive epigenetic and transcriptomic profile of the cells directly involved in the pathogenesis of GVHD and the GVT effect. Importantly, this method readily identifies the pathways that are dysregulated in the absence of DNMT3a. Aim 1: Target epigenetically regulated pathways to mitigate GVHD. Dnmt3a KO donor T-cells accelerate GVHD. WGBS and RNAseq post-HCT identified multiple pathways, normally silenced by DNMT3a, that may contribute to this phenomenon. We will explore these putative novel targets, starting with CCR9, a chemokine receptor that guides T-cells to the intestine, a major GVHD target organ. Aim 2: Determine the contribution of myeloid cell DNMT3a deletion to enhanced GVHD and GVT activity. Myeloid-derived cells hold significant immunoregulatory potential. The impact of myeloid DNMT3a deletion is unknown. We will use donors with myeloid Dnmt3a deletion to test this. Aim 3: Identify genes that distinguish beneficial GVT activity from harmful GVHD via epigenetic and transcriptomic comparative analyses. In GVT models, where allo-HCT is performed in the presence of leukemia, KO T-cells provide superior disease control. We will apply WGBS and RNAseq to interrogate how the presence of tumor alters the epigenome and identify the changes that allow KO T-cells to better eradicate leukemia. My long-term goal is to become an independent laboratory-based clinician-scientist, focusing on complications of HCT and novel therapeutic approaches. My aims and training plan have been s...