Abstract 6599: 3D genomic analysis reveals novel enhancer hijacking mechanisms caused by complex structural alterations that drive oncogene overexpression

Abstract Enhancer hijacking, caused by structural alterations on chromosomes as well as extrachromosomal DNA (ecDNA), is a common cancer driver event. The complexity and ubiquity of structural alterations in cancer genomes make it difficult to identify enhancer hijacking with genome sequencing alone. Here we describe a 3D genomics-based analysis called HAPI (Highly Active Promoter Interactions) to characterize enhancer hijacking caused by various types of structural alterations. Applying HAPI analysis to HiChIP data from 34 cancer cell lines, we identified novel enhancers hijacked through chromosomal rearrangements to activate both known and potentially novel oncogenes such as MYC, CCND1, ETV1, CRKL, and ID4, which we validated using CRISPRi assays and RNA-seq analysis. Furthermore, we found that ecDNAs often contain multiple oncogenes from different chromosomes, which cause nested enhancer hijacking among them. For instance, we found that MYC ecDNAs relocate additional oncogenes from other chromosomes such as CDX2, ERBB2, or CD44 near the MYC locus, co-opting MYC’s enhancers for their overexpression, which we validated using dual-color DNA FISH and CRISPRi assays. This multiple oncogenes-involved enhancer hijacking mechanism may suggest novel therapeutic strategies such as targeting either the co-opting oncogenes or the hijacked enhancers for ecDNAs. Our study provides a robust strategy to detect enhancer hijacking events using our publicly available HAPI analysis tool and reveals novel mechanisms underlying oncogene activation caused by chromosomal and extrachromosomal structural alterations. Citation Format: Katelyn L. Mortenson, Courtney Dawes, Emily R. Wilson, Nathan E. Patchen, Hailey Johnson, Jason Gertz, Swneke D. Bailey, Yan Liu, Katherine E. Varley, Xiaoyang Zhang. 3D genomic analysis reveals novel enhancer hijacking mechanisms caused by complex structural alterations that drive oncogene overexpression abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 6599.