PROJECT SUMMARY (Abstract) The importance of aberrant DNA methylation in cancer is clear. The fundamental role of DNA methylation in cancer initiation and progression, however, remains elusive. The use of gene targeting in animal models definitively demonstrated that genetic mutations at specific genes cause disease. An analogous “epigenetic gene targeting” approach is urgently needed to advance the field of epigenetics. In human lung cancers, p16 promoter methylation associated epigenetic silencing is one of the earliest detected epimutations and is thought to function as a critical initiating event in tumorigenesis. The importance of this epimutation is further underscored by the associations with distinct gene mutation patterns, cancer prognosis, and response to therapy. However, the molecular pathways linking aberrant DNA methylation, epigenetic silencing, and tumorigenesis remain poorly characterized. In this regard, we published the first mouse model demonstrating that targeted p16 epimutation drives spontaneous tumor development. Importantly, our preliminary studies revealed that p16 epimutation operates synergistically with oncogenic K-RAS activation to drive lung cancer progression. Based on these findings, this proposal responds to PAR-20-131: Research Projects to Enhance Applicability of Mammalian Models for Translational Research. Our overall goals are to establish more faithful murine models of human lung cancer development and to utilize this epigenetically engineered mouse model for testing novel epigenetic therapeutic strategies. Specifically, we will: 1 − Employing epigenetic engineering in mice to model advanced human lung cancers. We propose to establish clinically relevant and immunocompetent mouse models based on defined genetic and epigenetic alterations to drive benign lung tumor growths towards the ultimate malignant phenotype. 2 − Testing combinatorial epigenetic therapy in mouse lung tumors carrying a driver p16 epimutation. We propose to test whether epigenetic targeting drugs and/or anti-PD-L1 immunotherapy can effectively suppress p16 epimutant lung tumor growth during critical transition points from non-malignant lesions to adenocarcinoma. These studies will elucidate the functional role of epimutations in lung tumorigenesis in vivo. Successful completion of the proposed studies will provide a mechanistic rationale to refine ongoing epigenetic therapy, with the potential to improve survival rates in lung cancer.

PROJECT NARRATIVE (Relevance Statement) Epigenetics refers to the study of mitotically heritable changes in gene function without accompanying DNA sequence alterations; of the three known epigenetic mechanisms, DNA methylation stands out as the most stable epigenetic mark. The proposed research is relevant to public health because it will advance our understanding of how aberrant DNA methylation, frequently observed in lung cancer patients, drives tumor development. The proposed project will also contribute significantly to the ongoing search for new and improved strategies of cancer therapy and prevention.