Couch, Fergus J.

Abstract Familial studies were among the first to indicate that breast cancer prognosis has a heritable component. Subsequently many variants associated with prognosis have been identified using a range of techniques including genome-wide association studies (GWAs). Despite these advances, much of the heritability remains unexplained. In young women, breast cancer is characterised by a higher incidence of adverse pathological features, unique tumour gene expression profiles and worse survival. In addition, the association of risk with conventional epidemiological exposures is less clear in women with early onset. We hypothesise that some of these difference between early and late onset could be influenced by germline variation. To identify additional variants that influence breast cancer prognosis we conducted a two stage meta-analysis of four GWAs consisting of 6,042 patients from the UK (POSH), Finland (HEBCS), Germany (SUCCESS-A) and Australia (ABCFS). Cox-regression analyses were used to investigate overall survival (OS, n=1,101 events) and disease-free survival (DFS, n=1,316 events) with correction for oestrogen status (ER). These survival analyses were repeated in a subset of patients with early onset (aged ≤40 at diagnosis, n=2,315 patients, OS n=604 events, DFS n=716 events). Meta-analysis identified two intronic SNPs in ADAMTSL1 that were associated exclusively with early onset DFS, rs715212 (Pmeta=3.54x10-5) and rs10963755 (Pmeta=3.91x10-4) without heterogeneity between cohorts. Multivariable Cox-regression demonstrated that the effect of these SNPs were independent of the classical prognostic factors. Most importantly, rs715212 reached genome-wide significance (Pmultivariate=5.37x10-8) in the multivariate model. ADAMTSL1 encodes a glycoprotein that forms part of the extracellular matrix (ECM) and may function in cell-cell or cell-matrix interactions or may regulate other ADAMTS proteases. Previous studies have shown that ADAMTSL1 is hypermethylated in ER positive breast cancer tumours. Using GTEx to perform eQTL analysis, we found that rs715212 is associated with the expression of several biologically relevant genes AREG (P=0.035), TNF (P=0.015), FASLG (P=0.0031) and EGF (P=0.0018) in breast mammary tissue. Interestingly, separate studies have shown that AREG is overexpressed in ER-positive breast tumours from pre-menopausal women versus post-menopausal women. Furthermore, AREG is differentially expressed between parous and non-parous mammary glands and is persistently downregulated by parity, which suggests it may contribute to the susceptibility of the nulliparous gland to breast cancer. We conclude that rs715212 is associated with an increased risk of disease progression in patients with early onset and speculate that this could be due to an interaction with the expression of AREG. Note: This abstract was not presented at the meeting. Citation Format: Latha Kadalayil, Sofia Khan, Heli Nevanlinna, Peter A. Fasching, Fergus J. Couch, John Hopper, Jianjun Liu, Tom Maishman, Lorraine Durcan, Carl Bloomqvist, Andy Collins, Dianna Eccles, William Tapper. A meta-analysis of genome-wide association studies identifies novel loci that influence breast cancer prognosis [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 1322. doi:10.1158/1538-7445.AM2017-1322

Abstract Genome Wide Association Studies (GWAS) are designed to identify single nucleotide polymorphisms (SNPs) mapping to genomic regions associated with a particular trait or disease. Currently, 19 genomic loci associated with risk for estrogen receptor negative breast cancer have been identified. However, for most of these loci the mechanisms driving susceptibility have remained elusive. The 2p23.2 locus, defined by SNP rs67073037 (p = 4.76 x 10-9), contains 79 SNPs exhibiting genome-wide significant associations as well as four candidate genes: SPDYA, TRMT61B, WDR43, and FAM179A. Post-GWAS functional analysis revealed two candidate causal regulatory elements: an enhancer-like element defined by SNP rs44017214 located in the first intron of the WDR43 gene; and a segment in the 3’-UTR region of WDR43 defined by SNPs rs11680458 and rs11331880 which are predicted to have allele specific binding of non-coding microRNAs miR-548 and miR-376, respectively. We validated allele specific transcription factor binding to rs44017214 using competitive binding of USF1/USF2 to the risk allele in both MCF10A and CAL51 cell lines in Electrophoretic Mobility Shift Assays (EMSA). Additionally, rs44017214 was removed using CRISPR-cas9, and expression of neighboring genes was evaluated by qRT-PCR. No change in expression was found for any gene in a 2 Mb region surrounding the SNP, with the exception of PLB1. This suggests that the enhancer element in the intron of WDR43 has PLB1 as its target. To assess the miRNA binding site impact on WDR43 expression the pMIR-REPORT Luciferase allele-specific vector was co-transfected with miR-141/200, miR548, or miR-376 in MCF10A cells. The rs1131880 allele C in the WDR43 3’-UTR lead to the suppression of luciferase expression by miR-376 compared to the G allele. This study reveals two independent regulatory mechanisms within the 2p23.2 locus; (i) modulation of enhancer activity by allele specific binding of transcription factors USF1/USF2 to rs4401714, and (ii) decreasing the expression of WDR43 through the formation of a miR-376 binding site at the 3’-UTR of the WDR43 gene. Elucidating the functional significance of these common variants in the novel susceptibility loci 2p23.2 furthers our knowledge of the etiology of estrogen receptor negative breast cancer. Citation Format: Carly M. Harro, Gustavo Mendoza-Fandino, Nicholas T. Woods, Xueli Li, Fergus J. Couch, Alvaro N. Monteiro. Two distinct regulatory mechanisms underlie estrogen receptor negative breast cancer susceptibility at the 2p23.2 locus [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 1306. doi:10.1158/1538-7445.AM2017-1306

Abstract Germline pathogenic variants in BRCA1 and BRCA2 account for 10% of ovarian cancer (OC), including ovarian, fallopian tube, and primary peritoneal carcinomas. Pathogenic variants in BRIP1, RAD51C, RAD51D, and other cancer predisposition genes have been observed in another 2% to 5% of OCs. However, the specific genes associated with OC and estimates of risk associated with pathogenic variants in the individual genes are not well defined. We sought to determine the relevance of multigene panel testing results for OC cases. The study was focused on 140,449 individuals, including 10,233 OC cases, receiving clinical panel testing of cancer predisposition genes. Standardized relative risks (SRR) for pathogenic variants in 18 cancer predisposition genes were estimated using reference controls from the Exome Aggregation Consortium (ExAC). The median (range) age at diagnosis of OC was 57 (21-90) years. OC cases were 76.2% Caucasian, 3.6% African American, 4.6% Asian, 4.7% Hispanic, and 10.9% unknown/other. Among the 10,233 OC cases, 1391 (13.6%) had pathogenic mutations, including 1032 pathogenic mutations among the 7793 Caucasian OC cases (13.2%). Using the non-Finnish European ExAC (excluding TCGA samples) reference controls, the allele frequency for all pathogenic variants in each gene was summed and compared to the frequency of mutations in the Caucasian OC cases. Pathogenic variants in the known OC predisposition genes: BRCA1, BRCA2, BRIP1, MSH2, MSH6, RAD51C, and RAD51D were associated with a high risk of OC (SRR>4.0). Additionally, significant associations were observed for pathogenic variants in suspected OC risk genes ATM and PALB2 (SRR=2.06 and 2.78, respectively). This study identified several genes routinely screened on multigene panel testing that confer high or moderate risks of OC. Associations with known OC predisposition genes were confirmed. In addition, this study provides evidence that PALB2 is a moderate risk OC gene, and that ATM may confer lower to moderate risks of OC. If confirmed in future studies, these risks should be carefully considered in future screening and management of OC patients. In contrast, BARD1 and genes in the MRN complex were not associated with clinically relevant risks of OC. Citation Format: Jenna Lilyquist, Holly LaDuca, Eric Polley, Hermela Shimelis, Chunling Hu, Raymond Moore, Steven N. Hart, Fergus J. Couch, Jill Dolinsky, David E. Goldgar. Multigene panel testing and risk estimates in 10,233 ovarian cancer cases [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 1287. doi:10.1158/1538-7445.AM2017-1287

Investigating the most likely causal variants identified by fine‐mapping analyses may improve the power to detect gene–environment interactions. We assessed the interplay between 70 single nucleotide polymorphisms identified by genetic fine‐scale mapping of susceptibility loci and 11 epidemiological breast cancer risk factors in relation to breast cancer. Analyses were conducted on up to 58,573 subjects (26,968 cases and 31,605 controls) from the Breast Cancer Association Consortium, in one of the largest studies of its kind. Analyses were carried out separately for estrogen receptor (ER) positive (ER+) and ER negative (ER–) disease. The Bayesian False Discovery Probability (BFDP) was computed to assess the noteworthiness of the results. Four potential gene–environment interactions were identified as noteworthy (BFDP < 0.80) when assuming a true prior interaction probability of 0.01. The strongest interaction result in relation to overall breast cancer risk was found between CFLAR‐rs7558475 and current smoking (ORint = 0.77, 95% CI: 0.67–0.88, pint = 1.8 × 10−4). The interaction with the strongest statistical evidence was found between 5q14‐rs7707921 and alcohol consumption (ORint =1.36, 95% CI: 1.16–1.59, pint = 1.9 × 10−5) in relation to ER– disease risk. The remaining two gene–environment interactions were also identified in relation to ER– breast cancer risk and were found between 3p21‐rs6796502 and age at menarche (ORint = 1.26, 95% CI: 1.12–1.43, pint =1.8 × 10−4) and between 8q23‐rs13267382 and age at first full‐term pregnancy (ORint = 0.89, 95% CI: 0.83–0.95, pint = 5.2 × 10−4). While these results do not suggest any strong gene–environment interactions, our results may still be useful to inform experimental studies. These may in turn, shed light on the potential interactions observed.

Formalin-fixed paraffin-embedded (FFPE) specimens, when used in conjunction with patient clinical data history, represent an invaluable resource for molecular studies of cancer. Even though nucleic acids extracted from archived FFPE tissues are degraded, their molecular analysis has become possible. In this study, we optimized a laboratory-based next-generation sequencing barcoded cDNA library preparation protocol for analysis of small RNAs recovered from archived FFPE tissues. Using matched fresh and FFPE specimens, we evaluated the robustness and reproducibility of our optimized approach, as well as its applicability to archived clinical specimens stored for up to 35 years. We then evaluated this cDNA library preparation protocol by performing a miRNA expression analysis of archived breast ductal carcinoma in situ (DCIS) specimens, selected for their relation to the risk of subsequent breast cancer development and obtained from six different institutions. Our analyses identified six miRNAs (miR-29a, miR-221, miR-375, miR-184, miR-363, miR-455-5p) differentially expressed between DCIS lesions from women who subsequently developed an invasive breast cancer (cases) and women who did not develop invasive breast cancer within the same time interval (control). Our thorough evaluation and application of this laboratory-based miRNA sequencing analysis indicates that the preparation of small RNA cDNA libraries can reliably be performed on older, archived, clinically-classified specimens.

Abstract Breast cancer risks conferred by many germline missense variants in the BRCA1 and BRCA2 genes, often referred to as variants of uncertain significance (VUS), have not been established. In this study, associations between 19 BRCA1 and 33 BRCA2 missense substitution variants and breast cancer risk were investigated through a breast cancer case–control study using genotyping data from 38 studies of predominantly European ancestry (41,890 cases and 41,607 controls) and nine studies of Asian ancestry (6,269 cases and 6,624 controls). The BRCA2 c.9104A&gt;C, p.Tyr3035Ser (OR = 2.52; P = 0.04), and BRCA1 c.5096G&gt;A, p.Arg1699Gln (OR = 4.29; P = 0.009) variant were associated with moderately increased risks of breast cancer among Europeans, whereas BRCA2 c.7522G&gt;A, p.Gly2508Ser (OR = 2.68; P = 0.004), and c.8187G&gt;T, p.Lys2729Asn (OR = 1.4; P = 0.004) were associated with moderate and low risks of breast cancer among Asians. Functional characterization of the BRCA2 variants using four quantitative assays showed reduced BRCA2 activity for p.Tyr3035Ser compared with wild-type. Overall, our results show how BRCA2 missense variants that influence protein function can confer clinically relevant, moderately increased risks of breast cancer, with potential implications for risk management guidelines in women with these specific variants. Cancer Res; 77(11); 2789–99. ©2017 AACR.