Abstract P2-17-01: Targeted CRISPR screen to identify synthetic lethal combinations between APOBEC3B and DNA repair

Abstract APOBEC-catalyzed deamination of cytosine bases is the largest enzymatic and second largest overall source of mutation in cancer. One member from the APOBEC family of enzymes, APOBEC3B (A3B) is overexpressed and dysregulated in many different cancer types. In addition to hallmark C-to-T transitions and C-to-G transversions, APOBEC-catalyzed uracil lesions can be processed into single- and double-strand DNA breaks. Therefore, A3B-positive tumors are under continual stress to repair DNA breaks and may be vulnerable to DNA repair inhibition. Previous results from the Harris lab have identified UNG2, DNA uracil glycosylase 2 (UNG2), initiator of the base excision repair pathway, as synthetic lethal pair with A3B. The genetic disruption of UNG2 combined with high expression of A3B, causes cell death. This provides the rational to hypothesize that also other DNA repair proteins could be putative synthetic lethal pairs with A3B, when its expression and activity are high. To test this hypothesis, CRISPR guide RNA library targeting 237 DNA damage repair and response genes was used in doxycycline-inducible TREX-293-A3Bi-eGFP cell line. Cells expressing or not A3B were harvested for DNA extraction and sequencing at different time points. Comparison of guide RNA abundance between doxycycline and H2O treated cells revealed the dropout guides that disrupt genes and create putative synthetic lethal combinations with A3B. The screen design and overall results will be presented Citation Format: Bojana Stefanovska, Kevin Lin, Benjamin Troness, Chad Myers, Reuben Harris. Targeted CRISPR screen to identify synthetic lethal combinations between APOBEC3B and DNA repair [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-17-01.