Abstract 2482: Inhibition of RAD51 with a cell penetrating antibody, 3E10

Abstract

Abstract Many human malignancies arise in the setting of defective DNA repair pathways, leading to genetic instability, carcinogenesis and tumor progression. However, DNA repair deficiency can provide for a therapeutic window that can be exploited with targeted agents. One such anti-cancer agent is 3E10, a unique cell penetrating, anti-DNA autoantibody. 3E10 by itself is considered non-toxic to normal cells but has been shown to have deleterious effects on cells with DNA repair deficiencies. Specifically, 3E10 has been shown to reduce the efficiency of homologous recombination (HR). This has been attributed to its ability to preferentially binding to ssDNA tails, thereby inhibiting Rad51 mediated strand exchange. Prior work has shown that treatment with 3E10 alone can selectively kill cells with genetic mutations that lead to abnormal DNA repair. For example, 3E10 has been shown to be synthetically lethal in BRCA2 deficient human cancer cells. Additionally, 3E10 sensitizes cells to radiation and other DNA damaging therapies. The goal of this project is to characterize the specific mechanism by which 3E10 inhibits DNA repair pathways. Previously, the mechanism by which 3E10 inhibits HR was attributed to 3E10’s DNA binding ability. Through the biochemical evaluation of 3E10 variants, new evidence now suggests that 3E10 inhibits HR independently of 3E10’s ability to bind DNA. We have found that this HR inhibition is a result of a physical interaction between 3E10 and Rad51. Biochemical analysis revealed that 3E10 binds to the N-terminal domain of Rad51, the domain that plays a role in Rad51 homo-oligomerization and filament formation. This 3E10-Rad51 interaction impairs Rad51’s ability to localize to the nucleus and form repair foci. Taken together, this data suggests that 3E10 inhibits HR by physically interacting with Rad51. Overall, 3E10 holds promise as a novel therapeutic agent for certain subsets of cancer. Citation Format: Peter M. Glazer, Audrey Turchick. Inhibition of RAD51 with a cell penetrating antibody, 3E10 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2482. doi:10.1158/1538-7445.AM2017-2482