PROJECT SUMMARY Epigenetic mechanisms regulate chromatin structure and gene expression to direct organismal development and tissue homeostasis, disruption of which is pervasive in cancer. Epigenetic disruption can lead to the acquisition of each hallmark of cancer and almost half of all human cancers bear mutations in epigenetic regulators. Epigenetic mechanisms are also being increasingly appreciated as a major regulator of the tumor immune response prompting interest in finding ways to leverage this to benefit cancer patients. The histone modifiers KMT2C (MLL3) and KMT2D (MLL4) are amongst the most frequently mutated genes in all of cancer with particularly high rates of mutations in head and neck squamous cell carcinoma (HNSCC). Remarkably, despite the prevalence of KMT2C/D mutations and HNSCC, how KMT2C/D function during epithelial homeostasis and carcinogenesis remains unknown. My preliminary data suggest dysfunction of the KMT2C/D- H3K4me1 axis in the oral epithelium of mice in vivo results in oral epithelial hyperplasia. Given the inherent reversibility of epigenetic changes, these alterations may be targetable with inhibitors to prevent or treat HNSCC. My early thesis work supports this and suggests that dysfunction of the KMT2C/D-H3K4me1 axis may be corrected by inhibiting the opposing H3K4me1/2 histone demethylase LSD1. I hypothesize that loss of KMT2C/D disrupts oral epithelial homeostasis in vivo, promotes oral SCC carcinogenesis, and that these alterations may be reversed with LSD1 inhibitors. I will test this in the F99 phase of this fellowship as proposed in Aim 1. Specifically, I will study mice with deletions of Kmt2d or Kmt2c in the oral epithelium during homeostasis using histopathology, RNA-seq, and ChIP-seq. I will also test if loss of Kmt2c/d promotes epithelial carcinogenesis in vivo, employing a well-established model of oral carcinogenesis (4NQO), and if these alterations may be reversed using Lsd1 inhibitors. The goal of these studies is to identify if Kmt2c/d act as tumor suppressors in SCC and identify potential novel, epigenome targeting therapies for HNSCC patients. Despite the remarkable successes of immunotherapies, many patients do not respond to or become resistant to these treatments. Numerous studies have identified that epigenetic-targeting drugs may potentiate immunotherapies. However, how epigenetic mechanisms regulate tumor immunity during tumorigenesis or immunotherapy is incompletely understood. To this end, in the K00 phase of this fellowship as proposed in Aim 2, I will build upon my technical skills and scientific knowledge in cellular and tumor epigenetics by pursuing post-doctoral training in tumor immunology and immunoepigenetics. Specifically, I will determine how epigenetic alterations in tumor and immune cell populations regulate tumor immune competency, immune cell populations in the TME, and immune cell functions. Ultimately, these findings will identify how epigenetic mechanisms may be lever...