Functionally Null RAD51D Missense Mutation Associates Strongly with Ovarian Carcinoma

Barbara Rivera, Massimo Di Iorio, Jessica Frankum, Javad Nadaf, Somayyeh Fahiminiya, Suzanna L Arcand, David L Burk, Damien Grapton, Eva Tomiak, Valerie Hastings, Nancy Hamel, Rabea Wagener, Olga Aleynikova, Sylvie Giroux, Fadi F Hamdan, Alexandre Dionne-Laporte, George Zogopoulos, Francois Rousseau, Albert M Berghuis, Diane Provencher, Guy A Rouleau, Jacques L Michaud, Anne-Marie Mes-Masson, Jacek Majewski, Susanne Bens, Reiner Siebert, Steven A Narod, Mohammad R Akbari, Christopher J Lord, Patricia N Tonin, Alexandre Orthwein, William D Foulkes

RAD51D is a key player in DNA repair by homologous recombination (HR) and RAD51D truncating mutation carriers have an increased risk for ovarian cancer (OC). However, the contribution of non-truncating RAD51D variants to cancer predisposition remains uncertain. Using deep sequencing and case-control genotyping studies, we show that in French Canadians, the missense RAD51D variant c.620C>T;p.S207L is highly prevalent and is associated with a high risk for ovarian high-grade serous carcinoma (HGSC) (3.8% cases vs 0.2% controls). The frequency of the p.S207L variant did not significantly differ from that of controls in breast, endometrial, pancreas or colorectal adenocarcinomas. Functionally, we show for the first time that this mutation impairs HR by disrupting the RAD51D-XRCC2 interaction and confers PARP-inhibitor sensitivity. These results highlight the importance of a functional RAD51D-XRCC2 interaction to promote HR and prevent the development of HGSC. This study identifies c.620C>T;p.S207L as the first bona fide pathogenic RAD51D missense cancer susceptibility allele and supports the use of targeted PARP-inhibitor therapies in OC patients carrying deleterious missense RAD51D mutations.