Abstract 3002: Genome engineering approaches to generate models of chromosome arm-level cancer aneuploidy

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Abstract Aneuploidy, whole chromosome or chromosome arm copy number imbalance, is a near-universal characteristic of human cancers. Although yeast and mammalian models of whole chromosome aneuploidies have been extensively investigated, chromosome arm-level aneuploidies have rarely been modeled. Cancer subtypes are often characterized by tumor-specific patterns of these arm-level copy number alterations; for example, squamous cell carcinomas (SCCs) from different tissues of origin (including lung, esophagus, and bladder) have a pattern of chromosome 3p loss and chromosome 3q gain. Our analysis of 495 lung SCCs found chromosome 3p deletion to be the most frequent genomic alteration, occurring in almost 80% of the tumors and covering the entire length of the chromosome arm. Over two-thirds of chromosome 3p genes showed significantly decreased expression in these samples. Without models of chromosome arm-level alterations, the phenotypic effects of specific aneuploidies in cancer, such as 3p deletion, remain unknown. However, recent advances in genome engineering and targeting of endonucleases allow new approaches to generate chromosomal alterations. Here, we used the CRISPR-Cas9 system to delete one copy of chromosome 3p in vitro. We successfully isolated almost 90 clones of immortalized lung epithelial cells with deletion of the 3p arm, with 8 validated by whole-genome sequencing. Consistent with patient data, expression of 3p genes was also decreased upon deletion. Phenotypic characterization revealed that cells with chromosome 3p deletion initially proliferated more slowly than their siblings. These chromosome 3p-deleted cells had increased G1 arrest, but did not undergo increased apoptosis or cell death. Interestingly, after several passages in culture, the proliferation defect was rescued in chromosome 3p-deleted cells; genome sequencing and karyotype analyses suggested that this was the result of chromosome 3 duplication. With our cellular model of chromosome arm-level aneuploidy, we uncovered a possible selection mechanism that allows aneuploidy tolerance in vitro. We used genome engineering to model chromosome arm-level deletions, providing a robust model that will address a gap in our understanding of aneuploidy in cancer. Citation Format: Alison Marie Taylor, Xiaoyang Zhang, Juliann Shih, Gavin Ha, Galen F. Gao, Ashton C. Berger, Andrew D. Cherniack, Rameen Beroukhim, Matthew Meyerson. Genome engineering approaches to generate models of chromosome arm-level cancer aneuploidy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3002.