Abstract 417: Developing mouse models to dissect the function of a driver gene epimutation in lung tumorigenesis

Abstract

Abstract Background: Cancer is a complex disease caused by the accumulation of both genetic and epigenetic alterations in oncogenes and tumor suppressor genes. Although an extensive catalog of epigenetic changes has been generated in patients with lung cancer, we have only a fragmentary understanding of their functional roles, particularly for the initiation and maintenance of tumors. The use of genetically engineered mouse models definitively demonstrate that mutations at specific genes cause cancer. An analogous “epigenetically engineered mouse models” should not only lead to important insights about how cancer develop but could provide in vivo platforms in which to screen and validate novel epigenetic therapies. Methods and Results: We published the first epigenetically engineered mouse cancer model based on a driver gene epimutation of p16 (also known as cyclin-dependent kinase inhibitor 2A). In human lung cancers, p16 epimutation is common, occurring in ~50% of cases. Importantly, p16 epimutation is frequently detected in lung pre-neoplastic lesions and p16 is of the best documented gene that controls K-RAS oncogene-induced senescence. Therefore, to elucidate the functional role of p16 epimutation for lung cancer establishment and progression, we developed a mouse model that combines oncogenic K-ras with p16 epimutation. We found that mice with combined K-ras mutation and p16 epimutation (K-ras+/G12D; p16meth/meth) displayed substantially increased tumor numbers and sizes, with tumor progression to adenocarcinoma. In addition, to investigate the therapeutic effects of reversing p16 epimutation, we developed a mouse model that enables conditional and inducible CRISPR based epigenetic gene editing. Our system utilizes deactivated Cas9 (dCas9) fused to a repetitive protein scaffold known as SunTag, which recruits multiple copies of antibody-fused demethylase TET1. We showed that this system is robust and reproducible to achieve targeted DNA demethylation at CpGs within 100 bp from the sgRNA target site of p16 promoter and to reactivate p16. Conclusion: We have established clinically relevant and immunocompetent mouse models based on defined genetic and epigenetic alterations to drive benign lung tumor growths towards the ultimate malignant phenotype. Our model should prove useful as an in vivo preclinical platform for testing epigenetic therapeutic strategies. Citation Format: Li Yang, Anusha Mandala, Yi Chen, Lanlan Shen. Developing mouse models to dissect the function of a driver gene epimutation in lung tumorigenesis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 417.