Project Summary Recent investigations have revealed that oncogenic mutations are not sufficient for initial stages of tumorigenesis and that the microenvironment plays a significant role in promoting neoplastic growth of a tumor. This microenvironment surrounding a mutated cell can be influenced by many promotion processes, including environmental exposures, tissue damage, and chronic inflammation. This proposal aims to investigate the mechanisms by which promotion, or non-mutagenic processes, can influence the selection of mutant clones which eventually populate a tumor. This project will rely on theories from cancer genetics, tumor promotion, and evolutionary cancer biology in order to provide insight into the coordination between promotion and oncogenic mutations present in a cell. Through the use of a well-established model of chemical carcinogenesis, this project will address a fundamental question regarding the molecular consequences of tumor promotion. This carcinogenic regimen can produce both Hras mutant tumors and Kras mutant tumors, merely by adjusting the genetic background of the mouse. This provides the ideal tool for us to ask the question, what are the different promotion mechanisms which select for tumors with different mutations? To address this question, the proposed project aims to characterize promotion mechanisms on the backgrounds of the mice which are known to produce tumors with different mutations. The first aim will investigate how macrophage infiltration during promotion coordinates with oncogenic Hras signaling. This will be addressed by computationally identifying signaling axes between macrophages and epithelial cells from skin collected at different time points after application of a promoter. The second aim will define the active functional modules in the Kras-tumor-permissive skin, in response to a promoter. This will be achieved by constructing gene co-expression networks from single cell RNA sequencing of skin collected subsequent to promoter treatment in the skin. The proposed research will be completed by a graduate student with significant experience in both cancer biology and computational biology. It will be supervised by and conducted in the lab of Allan Balmain, an expert in the field of skin cancer genetics and tumor promotion. This training plan takes advantage of the highly collaborative and innovative research environment in the Helen Diller Family Comprehensive Cancer Center, which facilitates access to renowned scientific mentors and guidance in the proposed work. At the University of California, San Francisco (UCSF), the graduate program in Biomedical Sciences is regarded as one of the best due to its inclusion of professional development and training resources offered, which will support this highly motivated student to develop an independent research career. Completion of the proposed work will thus expand knowledge on a critical question in cancer biology and is enabled by an excellent institut...