Abstract PHA04: A new somatic engineering-based model of small-cell lung cancer development

Abstract

Abstract Defining the cancer genome is essential for understanding the pathogenesis, but it remains challenging due to the paucity of robust models for characterizing recurrent mutations found in cancer. To understand the molecular mechanisms underlying the development of small-cell lung cancer (SCLC), an aggressive type of lung cancer initiated by inactivation of both RB and P53, it is important to determine the functional impact of recurrent mutations found in the patient tumors. To this end, we developed a somatic engineering approach, using a CRISPR/Cre hybrid tool that expresses guide RNA, Cas9 endonuclease, and Cre recombinase from a single adenoviral vector (Ad-target of gRNA-CRISPR/Cre). Intratracheal instillation of this recombinant virus causes mutation in a candidate tumor suppressor gene while recombining floxed alleles of Rb1, Trp53, and Rbl2 in the same epithelial cell. To determine functions of Ep300, Slit2, and Fhit, whose orthologous genes are frequently mutated in SCLC patient tumors, we infect the Rb1/Trp53/Rbl2 conditional mice with the viral vectors carrying gRNAs against these genes. The mice infected with Ad-Ep300-CRISPR/Cre or Ad-Fhit-CRISPR/Cre have higher tumor burden in the lungs than those infected with Ad-lacZ-CRISPR/Cre used as control. Although Slit2 is significantly mutated in SCLC, the mice infected with Ad-Slit2-CRISPR/Cre do not increase tumor burden relative to those with Ad-lacZ-CRISPR/Cre. These results for the first time validate the oncogenic impact of Ep300 and Fhit mutations. This study demonstrates the feasibility and robustness of a new somatic engineering-based model for characterizing candidate mutations, which will facilitate the discovery of key oncogenic drivers and pathways from the large number of novel somatic alterations in SCLC. Ongoing efforts with this new approach are focused on validation of functionally unknown mutations alone or in combinations. This abstract is also being presented as Poster A39. Citation Format: Kee-Beom Kim, Dong-Wook Kim, Kwon-Sik Park. A new somatic engineering-based model of small-cell lung cancer development [abstract]. In: Proceedings of the AACR Special Conference on the Evolving Landscape of Cancer Modeling; 2020 Mar 2-5; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2020;80(11 Suppl):Abstract nr PHA04.