Project Summary/Abstract This proposal details a five year training plan for the development of a research program focused on non-genetic mechanisms of therapy resistance in melanoma. Therapies that target the MAPK pathway in melanoma have remarkable success in shrinking patients’ initial tumors but disease recurs, often without new mutations that explain therapy failure. This appears to be due to a small population of rare cells present in the initial tumor that display high levels of resistance genes such as epidermal growth factor receptor (EGFR) and are not killed by initial MAPK targeted therapy. The mechanisms that drive formation of these rare pre-resistant cells are unknown, though preliminary studies implicate gene regulation by enhancers. The goals of this research proposal are to characterize the key genetic pathways that define pre-resistant cells in patient tumors, identify enhancers that drive expression of resistance genes and cellular variation, and to identify pharmacologic targets for preventing therapy resistance. Since EGFR plays an important role in many cancers and non-genetic variation appears to undergird treatment failure in many different malignancies, the implications of this work for human disease may be far-reaching. The work will be mentored by Phillip A. Sharp at the Massachusetts Institute of Technology, a leader in understanding gene regulation in cancer and whose laboratory has produced numerous distinguished alumni. I am a practicing molecular pathologist at the Massachusetts General Hospital interested in how variation arises naturally within biological systems. In diagnostic pathology, we are attempting to achieve ever greater ‘personalized medicine’ in cancer treatment using sequencing. To achieve the best precision medicine possible, we must understand the mechanisms by which tumors evade therapy that go beyond genetic changes such as mutations. This will allow us to build better, more accurate diagnostics and give our oncologist colleagues the best actionable information. My career objective during the proposal period is to obtain a tenure-track position at an academic medical center continuing work as a Principal Investigator. Specifically, during the proposal period I will gain experience with melanoma model systems, enhancer biology, genomics, and systems biology approaches. My long term objective is to define how variation and heterogeneity arise within biological systems and how we can diagnose and manipulate these processes in human disease.