Hiltrud Brauch

CYP19A1 fine-mapping and Mendelian randomization: estradiol is causal for endometrial cancer

Candidate gene studies have reported CYP19A1 variants to be associated with endometrial cancer and with estradiol (E2) concentrations. We analyzed 2937 single nucleotide polymorphisms (SNPs) in 6608 endometrial cancer cases and 37u200a925 controls and report the first genome wide-significant association between endometrial cancer and a CYP19A1 SNP (rs727479 in intron 2, P=4.8×10−11). SNP rs727479 was also among those most strongly associated with circulating E2 concentrations in 2767 post-menopausal controls (P=7.4×10−8). The observed endometrial cancer odds ratio per rs727479 A-allele (1.15, CI=1.11–1.21) is compatible with that predicted by the observed effect on E2 concentrations (1.09, CI=1.03–1.21), consistent with the hypothesis that endometrial cancer risk is driven by E2. From 28 candidate-causal SNPs, 12 co-located with three putative gene-regulatory elements and their risk alleles associated with higher CYP19A1 expression in bioinformatical analyses. For both phenotypes, the associations with rs727479 were stronger among women with a higher BMI (Pinteraction=0.034 and 0.066 respectively), suggesting a biologically plausible gene-environment interaction.

Genetic modifiers of CHEK2*1100delC-associated breast cancer risk

Purpose:CHEK2*1100delC is a founder variant in European populations that confers a two- to threefold increased risk of breast cancer (BC). Epidemiologic and family studies have suggested that the risk associated with CHEK2*1100delC is modified by other genetic factors in a multiplicative fashion. We have investigated this empirically using data from the Breast Cancer Association Consortium (BCAC).Methods:Using genotype data from 39,139 (624 1100delC carriers) BC patients and 40,063 (224) healthy controls from 32 BCAC studies, we analyzed the combined risk effects of CHEK2*1100delC and 77 common variants in terms of a polygenic risk score (PRS) and pairwise interaction.Results:The PRS conferred odds ratios (OR) of 1.59 (95% CI: 1.21–2.09) per standard deviation for BC for CHEK2*1100delC carriers and 1.58 (1.55–1.62) for noncarriers. No evidence of deviation from the multiplicative model was found. The OR for the highest quintile of the PRS was 2.03 (0.86–4.78) for CHEK2*1100delC carriers, placing them in the high risk category according to UK NICE guidelines. The OR for the lowest quintile was 0.52 (0.16–1.74), indicating a lifetime risk close to the population average.Conclusion:Our results confirm the multiplicative nature of risk effects conferred by CHEK2*1100delC and the common susceptibility variants. Furthermore, the PRS could identify carriers at a high lifetime risk for clinical actions.Genet Med advance online publication 06 October 2016

Association of breast cancer risk with genetic variants showing differential allelic expression: Identification of a novel breast cancer susceptibility locus at 4q21

There are significant inter-individual differences in the levels of gene expression. Through modulation of gene expression, cis-acting variants represent an important source of phenotypic variation. Consequently, cis-regulatory SNPs associated with differential allelic expression are functional candidates for further investigation as disease-causing variants. To investigate whether common variants associated with differential allelic expression were involved in breast cancer susceptibility, a list of genes was established on the basis of their involvement in cancer related pathways and/or mechanisms. Thereafter, using data from a genome-wide map of allelic expression associated SNPs, 313 genetic variants were selected and their association with breast cancer risk was then evaluated in 46,451 breast cancer cases and 42,599 controls of European ancestry ascertained from 41 studies participating in the Breast Cancer Association Consortium. The associations were evaluated with overall breast cancer risk and with estrogen receptor negative and positive disease. One novel breast cancer susceptibility locus on 4q21 (rs11099601) was identified (OR = 1.05, P = 5.6x10-6). rs11099601 lies in a 135 kb linkage disequilibrium block containing several genes, including, HELQ, encoding the protein HEL308 a DNA dependant ATPase and DNA Helicase involved in DNA repair, MRPS18C encoding the Mitochondrial Ribosomal Protein S18C and FAM175A (ABRAXAS), encoding a BRCA1 BRCT domain-interacting protein involved in DNA damage response and double-strand break (DSB) repair. Expression QTL analysis in breast cancer tissue showed rs11099601 to be associated with HELQ (P = 8.28x10-14), MRPS18C (P = 1.94x10-27) and FAM175A (P = 3.83x10-3), explaining about 20%, 14% and 1%, respectively of the variance inexpression of these genes in breast carcinomas.

Abstract 2030: The role of genetic variation in calcium-activated potassium channels in breast cancer patients treated with tamoxifen

Potassium channels control membrane voltage and are essential for cell proliferation. Abnormal regulation and/or expression of these channels have been reported in cancer and result in dysregulated cell cycle progression, cell proliferation and migration. In breast cancer, clinical correlations of potassium channels have been associated with brain metastases, high stage, high grade, high proliferation, nodal status and poor prognosis. Interestingly, they have been associated with increased estrogen receptor (ER) expression. The selective ER modulator, tamoxifen, blocks estrogen from binding to the ER and is commonly used to treat patients with ER-positive breast cancer. However, up to 33% of patients treated with tamoxifen relapse or dies at 15 years of follow up. Both estrogen and tamoxifen have been demonstrated to activate potassium channels which then cause an increase in cell proliferation. In preliminary animal in vivo studies, we observed a better breast cancer prognosis in those with a knockout in potassium channel genes. Therefore, any alterations in the potassium channels may help to explain why patients treated with tamoxifen fail therapy. We hypothesized that genetic variation in potassium channels may affect breast cancer risk as well as tamoxifen treatment outcome. Genotyping was conducted on 45,290 breast cancer patients and 41,880 controls of European ancestry from 41 studies with the custom Illumina Infinium array (iCOGS). More than 200,000 SNPs were genotyped with over 11 million SNPs estimated using genotype imputation with SHAPEIT and IMPUTEv2 and the 1000 Genomes Project March 2012 release as the reference panel (Michailidou et al. Nature Genetics 2015). Variants from 13 potassium channels including KCNMA1, KCNMB1-4, KCNN1-4, LRRC26, LRRC38, LRRC52 and LRRC55 were analyzed. Of these, 3 imputed SNPs from KCNN4 have shown decreased breast cancer risk with GWAS significance (rs12463319, rs12609846, rs1685191; OR 0.94, P 0.05). These findings encouraged us to now further investigate the outcomes of patients with ER-positive breast cancer treated with tamoxifen. Survival data for 49,751 patients with a median follow-up of 8 years has been completed and released in November 2015. Of these, 32,571 were ER-positive and 10,383 have been treated with tamoxifen. Current efforts are underway in order to determine the effects of genetic variations in potassium channels on the survival of patients treated with tamoxifen. Our work will provide a better understanding of the potential clinical relevance of potassium channels in tamoxifen treatment in breast cancer. Citation Format: Wing-Yee Lo, Corinna Mohr, Friederike Steudel, Marjanka Schmidt, Douglas Easton, Reiner Hoppe, Werner Schroth, Peter Ruth, Robert Lukowski, Hiltrud Brauch, in collaboration with the Breast Cancer Association Consortium. The role of genetic variation in calcium-activated potassium channels in breast cancer patients treated with tamoxifen. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2030.

Abstract 1073: Modulation of aromatase inhibitor resistance by miRNAs in breast cancer

Proceedings: AACR 107th Annual Meeting 2016; April 16-20, 2016; New Orleans, LAnnThe blockade of E2 signaling by either tamoxifen or aromatase inhibitors (AI) is the standard treatment of patients with estrogen receptor (ER)-positive breast cancer. However, acquired resistance to antiestrogen therapies remains a big clinical challenge. The in vitro breast cancer models MCF-7:5C and MCF-7:2A mimic clinical AI resistance in that they grow under tamoxifen, but can rapidly regress with E2 due to the reconfiguration of survival signaling known as E2-inducible apoptosis. This principle is currently explored in clinical trials in order to develop strategies to overcome endocrine resistance. To better understand the biology of AI resistance we previously ascertained a wide range of alterations of stress related pathways including the accumulation of endoplasmic reticulum stress, oxidative stress, and inflammatory stress that occur prior to E2-induced apoptosis (Ariazi et al. 2011; Fan et al. 2013, 2015; Sweeney et al. 2014). In this current work we investigated miRNA expression profiles of the 5C and 2A models (both compared to MCF-7:WS8 reference) in order to further elucidate the molecular scenario that characterizes the AI resistance phenotypes and their susceptibility to E2-induced apoptosis. Using Affymetrix GeneChip miRNA2.0 arrays we identified 184 miRNAs differentially expressed between 2A and 5C (FC > 1.5 or < 1/1.5, P < 0.05). Of these, 30 miRNAs were specific for 2A, 99 for 5C, and 55 overlapped. Common miRNAs include upregulated oncogenic miRNAs of the miR-17-92 cluster (Chr. 13q31) and the paralogous 106a-363 cluster (Chr. X), as well as downregulated tumor suppressive miRNAs such as miR-342-5p. Thirty-four miRNAs that cluster at Chr. 14q32 were overexpressed in 5C cells and highly correlate with the downregulated miR-99a and miR-125b (Chr. 21q21). At the clinical level based on data from The Cancer Genome Atlas (miRNA-Seq v. 3.1.17.0), low expression of miR-31 was associated with poor (HR = 3.0, 95% CI: 1.9-4.8; Padj = 8.7E-5), and low miR-222 expression was associated with better outcome (HR = 0.3, 95% CI: 0.1-0.6; Padj. = 4.4E-3). As miR-31 expression is high and miR-222 expression is low in 5C cells compared to the MCF-7:WS8 reference, we suggest protective roles. Functions of miRNAs were deciphered via analyses of their predicted targets (CLIP-confirmed). Using KEGG and GO databases functional enrichment analyses of 5C and 2A specific miRNA sets revealed pathways associated with cell proliferation for both models including insulin, mTOR, and ErbB signaling as well as immune response and metabolism associated pathways. While the 2A specific miRNA set revealed additional metabolic pathways, the 5C specific miRNA set points to pathways involved in apoptosis. Thus, we confirmed the biological processes inherent to AI resistance and provide critical evidence for miRNA profiles as an important regulatory principle in these AI resistance models.nnCitation Format: Reiner Hoppe, Ping Fan, Florian Buttner, Stefan Winter, Heather Cunliffe, V. Craig Jordan, Hiltrud B. Brauch. Modulation of aromatase inhibitor resistance by miRNAs in breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1073.