Abstract 365: Detection of homologous recombination deficiency across cancer types by a real-time activity-based functional biomarker

Abstract

Abstract Homologous recombination (HR) is an error-free repair pathway to eliminate DNA double-strand breaks and crucial for maintaining genome stability. Pathogenic mutations in genes involved in HR, such as BRCA1 and BRCA2, lead to homologous recombination deficiency (HRD) and sensitive cells to poly(ADP-ribose) polymerase inhibitors (PARPi). As such, the selection of HRD cancer patients becomes an important clinical need. In addition to sequencing HR-related genes, recent studies have developed several approaches to detect HRD including genomic scar score, mutational signatures analysis, and RAD51 foci formation assay. However, these assays are not on a real-time basis and provide an indirect estimation of HR status. To overcome these limitations, we have successfully developed a virus-based functional assay to directly quantify HR activity in cells. Our method detects HR status in a real-time and tumor-only manner. By using this activity-based functional assay, we reveal a universal activity threshold for identifying HRD across cancer types. Here, we present a promising method to accurately detect primary ovarian cancer cells with HRD. Clinical samples that be quantified as HRD show a significant response to PARPi. Therefore, our method can serve as a functional biomarker and companion diagnostic for PARPi. Citation Format: Chih-Ying Lee, Kai-Hang Lei, Shih-Han Huang, Min-Yu Ko, Ko-Yu Chang, Po-Han Lin, Yu-Li Chen, Wen-Fang Cheng, Peter Chi. Detection of homologous recombination deficiency across cancer types by a real-time activity-based functional biomarker [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 365.