Mitchell, Gillian

Background BRCA1 interacting protein C-terminal helicase 1 (BRIP1) is one of the Fanconi Anaemia Complementation (FANC) group family of DNA repair proteins. Biallelic mutations in BRIP1 are responsible for FANC group J, and previous studies have also suggested that rare protein truncating variants in BRIP1 are associated with an increased risk of breast cancer. These studies have led to inclusion of BRIP1 on targeted sequencing panels for breast cancer risk prediction. Methods We evaluated a truncating variant, p.Arg798Ter (rs137852986), and 10 missense variants of BRIP1, in 48 144 cases and 43 607 controls of European origin, drawn from 41 studies participating in the Breast Cancer Association Consortium (BCAC). Additionally, we sequenced the coding regions of BRIP1 in 13 213 cases and 5242 controls from the UK, 1313 cases and 1123 controls from three population-based studies as part of the Breast Cancer Family Registry, and 1853 familial cases and 2001 controls from Australia. Results The rare truncating allele of rs137852986 was observed in 23 cases and 18 controls in Europeans in BCAC (OR 1.09, 95% CI 0.58 to 2.03, p=0.79). Truncating variants were found in the sequencing studies in 34 cases (0.21%) and 19 controls (0.23%) (combined OR 0.90, 95% CI 0.48 to 1.70, p=0.75). Conclusions These results suggest that truncating variants in BRIP1, and in particular p.Arg798Ter, are not associated with a substantial increase in breast cancer risk. Such observations have important implications for the reporting of results from breast cancer screening panels.

Abstract Background: Treatment options for women with ovarian cancer remain very limited and acquired resistance to current therapies is very common. Altered DNA repair capability in epithelial ovarian cancer (EOC) may underlie response to both standard therapy and novel treatments, such as PARP inhibitors. Molecular sub-classification of high-grade serous ovarian cancer (HG-SOC) may uncover potential drug targets and possible mechanisms of drug resistance. Understanding the contribution of DNA repair and other driver mutations to drug response and resistance requires the development of molecularly annotated preclinical models reflective of the clinic. Methods: A patient derived xenograft (PDX) cohort has been generated from consecutive, chemotherapy-naïve human HG-SOC and stratified according to in vivo response to standard chemotherapy, DNA repair capability and molecular characteristics, including next generation sequencing by Foundation Medicine. Resistance to therapy is driven by re-treating relapsed PDX in vivo providing invaluable “paired samples” (pre and post drug treatment), which are difficult to obtain from patients, to allow clonal evolution analysis of mechanisms of drug response and resistance. Results: The xenograft success rate was 83%. Of ten HG-SOC PDX, all exhibited mutations in TP53, five in BRCA1/2 (two of which were germline) and two were methylated for BRCA1. In vivo cisplatin response, determined as platinum sensitive (progression-free interval (PFI) ≥100 d, n=4), platinum resistant (PFI <100 d, n=3) or platinum refractory (n=3), was largely consistent with patient outcome. Three of four platinum sensitive HG-SOC PDX contained DNA repair gene mutations, and the fourth was methylated for BRCA1. In contrast, all three platinum refractory PDX overexpressed dominant oncogenes (CCNE1, LIN28B and/or BCL2). Molecular analysis of this cohort has revealed actionable targets for novel therapeutic strategies. In vivo studies, including with PARP inhibitors, are underway. Conclusion: PDX with histologic, molecular and therapeutic annotation, as well as clinical outcome data allow interrogation of molecular aberrations and drug resistance in vivo. This will inform targeting of novel therapies and the design of clinical trials for women. Citation Format: Monique D. Topp, Lynne Hartley, Michele Cook, Valerie Heong, Emma Boehm, Lauren McShane, Jan Pyman, Orla McNally, Sumi Ananda, Maria I. Harell, Dariush Etemadmoghadam, Laura Galletta, Kathryn Alsop, Gillian Mitchell, Stephen B. Fox, Jeff B. Kerr, Karla J. Hutt, Scott H. Kaufmann, Australian Ovarian Cancer Study (AOCS), Elizabeth M. Swisher, David D. Bowtell, Matthew M. Wakefield, Clare L. Scott. Using molecularly characterized patient-derived models to delineate underlying drivers and vulnerabilities of epithelial ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference: Cancer Susceptibility and Cancer Susceptibility Syndromes; Jan 29-Feb 1, 2014; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(23 Suppl):Abstract nr 38. doi:10.1158/1538-7445.CANSUSC14-38

Abstract Purpose: To analyze the effect of germline mutations in BRCA1 and BRCA2 on mortality in patients with ovarian cancer up to 10 years after diagnosis. Experimental Design: We used unpublished survival time data for 2,242 patients from two case–control studies and extended survival time data for 4,314 patients from previously reported studies. All participants had been screened for deleterious germline mutations in BRCA1 and BRCA2. Survival time was analyzed for the combined data using Cox proportional hazard models with BRCA1 and BRCA2 as time-varying covariates. Competing risks were analyzed using Fine and Gray model. Results: The combined 10-year overall survival rate was 30% [95% confidence interval (CI), 28%–31%] for non-carriers, 25% (95% CI, 22%–28%) for BRCA1 carriers, and 35% (95% CI, 30%–41%) for BRCA2 carriers. The HR for BRCA1 was 0.53 at time zero and increased over time becoming greater than one at 4.8 years. For BRCA2, the HR was 0.42 at time zero and increased over time (predicted to become greater than 1 at 10.5 years). The results were similar when restricted to 3,202 patients with high-grade serous tumors and to ovarian cancer–specific mortality. Conclusions: BRCA1/2 mutations are associated with better short-term survival, but this advantage decreases over time and in BRCA1 carriers is eventually reversed. This may have important implications for therapy of both primary and relapsed disease and for analysis of long-term survival in clinical trials of new agents, particularly those that are effective in BRCA1/2 mutation carriers. Clin Cancer Res; 21(3); 652–7. ©2014 AACR.