African American Breast Cancer Epidemiology Research Articles

Influence of alcohol consumption and alcohol metabolism variants on breast cancer risk among Black women: results from the AMBER consortium

BackgroundModerate to heavy alcohol consumption is associated with an increased risk of breast cancer. The etiologic role of genetic variation in genes involved in ethanol metabolism has not been established, with little information available among women of African ancestry.MethodsOur analysis from the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium included 2889 U.S. Black women who were current drinkers at the time of breast cancer diagnosis (N cases = 715) and had available genetic data for four ethanol metabolism genomic regions (ADH, ALDH, CYP2E1, and ALDH2). We used generalized estimating equations to calculate genetic effects, gene* alcohol consumption (≥ 7drinks/week vs. < 7/week) interactions, and joint main plus interaction effects of up to 23,247 variants in ethanol metabolism genomic regions on odds of breast cancer.ResultsAmong current drinkers, 21% of cases and 14% of controls reported consuming ≥ 7 drinks per week. We identified statistically significant genetic effects for rs79865122-C in CYP2E1 with odds of ER- breast cancer and odds of triple negative breast cancer, as well as a significant joint effect with odds of ER- breast cancer (≥ 7drinks per week OR = 3.92, < 7 drinks per week OR = 0.24, pjoint = 3.74 × 10−6). In addition, there was a statistically significant interaction of rs3858704-A in ALDH2 with consumption of ≥ 7 drinks/week on odds of triple negative breast cancer (≥ 7drinks per week OR = 4.41, < 7 drinks per week OR = 0.57, pint = 8.97 × 10–5).ConclusionsThere is a paucity of information on the impact of genetic variation in alcohol metabolism genes on odds of breast cancer among Black women. Our analysis of variants in four genomic regions harboring ethanol metabolism genes in a large consortium of U.S. Black women identified significant associations between rs79865122-C in CYP2E1 and odds of ER- and triple negative breast cancer. Replication of these findings is warranted.

Dietary Vitamin A and Breast Cancer Risk in Black Women: The African American Breast Cancer Epidemiology and Risk (AMBER) Consortium

BackgroundStudies in women of European descent showed an inverse association of dietary vitamin A (retinol and carotenoids) intake with breast cancer risks, mainly in premenopausal women. ObjectivesWe examined whether higher compared with lower levels of dietary vitamin A are associated with reduced breast cancer risks among Black women by estrogen receptor (ER) and menopausal statuses. MethodsIn this pooled analysis, data were from 3564 breast cancer cases and 11,843 controls (mean ages = 56.4 and 56.3 years, respectively) in the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium. Dietary intake was assessed by FFQs. Multivariable logistic regressions were performed to estimate ORs and 95% CIs for study-specific quintiles of total vitamin A equivalents and individual carotenoids, and a pooled OR was estimated by a random-effect model. ResultsWe observed an inverse association of total vitamin A equivalents with ER-positive breast cancer (quintiles 5 compared with 1: pooled OR: 0.82; 95% CI: 0.67–1.00; P-trend = 0.045). The association was seen among premenopausal women (pooled OR: 0.60; 95% CI: 0.43–0.83; P-trend = 0.004), but not among postmenopausal women (pooled OR: 0.99; 95% CI: 0.77–1.28; P-trend = 0.78). Additionally, there were inverse associations of dietary β-carotene (quintiles 5 compared with 1: pooled OR: 0.70; 95% CI: 0.51–0.95; P-trend = 0.08) and lutein (pooled OR: 0.63; 95% CI: 0.45–0.87; P-trend = 0.020) with ER-positive breast cancer among premenopausal women. There was no evidence for an association of total vitamin A equivalents or individual carotenoids with ER-negative breast cancer, regardless of menopausal status. ConclusionsOur findings on dietary vitamin A and breast cancer risks in Black women are consistent with observations in women of European descent and advance the literature showing an inverse association for ER-positive disease.

Epidemiology of Basal-like and Luminal Breast Cancers among Black Women in the AMBER Consortium.

Evidence suggests etiologic heterogeneity among breast cancer subtypes. Previous studies with six-marker IHC classification of intrinsic subtypes included small numbers of black women. Using centralized laboratory results for estrogen receptor (ER), progesterone receptor, HER2, proliferation marker, Ki-67, EGFR, and cytokeratin (CK)5/6, we estimated case-only and case-control ORs for established breast cancer risk factors among cases (n = 2,354) and controls (n = 2,932) in the African American Breast Cancer Epidemiology and Risk (AMBER) consortium. ORs were estimated by ER status and intrinsic subtype using adjusted logistic regression. Case-only analyses by ER status showed etiologic heterogeneity by age at menarche, parity (vs. nulliparity), and age at first birth. In case-control analyses for intrinsic subtype, increased body mass index and waist-to-hip ratio (WHR) were associated with increased risk of luminal A subtype, whereas older age at menarche and parity, regardless of breastfeeding, were associated with reduced risk. For basal-like cancers, parity without breastfeeding and increasing WHR were associated with increased risk, whereas breastfeeding and age ≥25 years at first birth were associated with reduced risk among parous women. Basal-like and ER-/HER2+ subtypes had earlier age-at-incidence distribution relative to luminal subtypes. Breast cancer subtypes showed distinct etiologic profiles in the AMBER consortium, a study of more than 5,000 black women with centrally assessed tumor biospecimens. Among black women, high WHR and parity without breastfeeding are emerging as important intervention points to reduce the incidence of basal-like breast cancer.

Risk factors for estrogen receptor positive ductal carcinoma in situ of the breast in African American women

BackgroundCompared to U.S. white women, African American women are more likely to die from ductal carcinoma in situ (DCIS). Elucidation of risk factors for DCIS in African American women may provide opportunities for risk reduction. MethodsWe used data from three epidemiologic studies in the African American Breast Cancer Epidemiology and Risk Consortium to study risk factors for estrogen receptor (ER) positive DCIS (488 cases; 13,830 controls). Results were compared to associations observed for ER+ invasive breast cancer (n = 2,099). ResultsFirst degree family history of breast cancer was associated with increased risk of ER+ DCIS [odds ratio (OR): 1.69, 95% confidence interval (CI): 1.31, 2.17]. Oral contraceptive use within the past 10 years (vs. never) was also associated with increased risk (OR: 1.43, 95%CI: 1.03, 1.97), as was late age at first birth (≥25 years vs. <20 years) (OR: 1.26, 95%CI: 0.96, 1.67). Risk was reduced in women with older age at menarche (≥15 years vs. <11 years) (OR: 0.62, 95%CI: 0.42, 0.93) and higher body mass index (BMI) in early adulthood (≥25 vs. <20 kg/m2 at age 18 or 21) (OR: 0.75, 95%CI: 0.55, 1.01). There was a positive association of recent BMI with risk in postmenopausal women only. In general, associations of risk factors for ER+ DCIS were similar in magnitude and direction to those for invasive ER+ breast cancer. ConclusionsOur findings suggest that most risk factors for invasive ER+ breast cancer are also associated with increased risk of ER+ DCIS among African American women.

Abstract 226: Single variant and gene-based replication analysis of reproductive aging in African American women in the AMBER Consortium

Abstract The two main hormonal events of a woman's life, menarche and menopause, have a paramount impact on the duration of exposure to estrogen. Reproductive aging phenotypes, including age at menarche (AM) and age at natural menopause (ANM) have been consistently associated with breast cancer risk. Despite an estimated strong genetic component, genome-wide association studies (GWAS) for AM and ANM found that common variants identified to date account for only 7.4% for SNPs related to AM and 2.5-4.1% for ANM. As most previous GWAS on AM and ANM were conducted in women of European ancestry (EA), studies examining genetic components of reproductive aging in African-American (AA) women are needed. We hypothesize that although the index GWAS variants discovered in EA women may differ from those in AA women, rare and low-frequency causal variants may reside in the same genetic regions. A candidate analysis of previously identified GWAS variants and genes in association with AM, ANM was conducted in the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium. All SNPs within a 500kb window of previously discovered GWAS SNPs for AM and ANM were extracted from the Illumina Human Exome Beadchip v1.1, leading to 1,505 candidate SNPs from 125 genes for AM and 1,198 candidate SNPs from 35 genes for ANM in a total of 7,886 AA subjects. Single SNP association tests were run in PLINK using linear regressions for the continuous trend test for AM/ANM and logistic regression for the extreme AM phenotype (&amp;lt;11 v. &amp;gt;=≥15 years). The SKAT-O test for the gene-based analyses was performed using the SKAT R package to aggregate variants with an MAF upper bound of 5%. The top variants related to AM were two SNPs, rs314277 (β=0.11, MAF= 0.45, p=6.24E-05) and rs4742314 (β= -0.11, MAF= 0.39, p=6.44E-05), located in LIN28B and KDM4C respectively. rs974828 (RORA, MAF= 0.23, OR=0.71, p=0.0003) and rs314277 (p=0.0007) were found to be the top variants in association with the extreme AM phenotype. For ANM, rs16991615, located in MCM8, was the most significant variant associated with increased ANM ((β=2.06, MAF= 0.01, p=0.0005). rs314277 (LIN28B) has been previously associated with AM, and rs16991615 (MCM8) had also been related to ANM in previous GWAS in EAs. In gene-based analysis for AM, SLC38A3 (p=0.0007) and WDR6 (p= 0.003) were nominally significant; and EPS8L1 (p= 0.005) and RBM6 (p= 0.01) were associated with the AM phenotype. For ANM, RBMS2 (p= 0.006) was nominally significant in gene-based analysis. This is to date the largest study in AA women for reproductive life events to interrogate rare and low-frequency variants, which are beyond the spectrum of common variants in previous GWAS. Although the overall replication success rate is low, our analyses identified several rare and low-frequency variants in regions from previous GWAS. Our data contributed to the literature on genetic variation for reproductive aging in AA women. Citation Format: Marie V. Coignet, Qianqian Zhu, David G. Cox, Kathryn Lunetta, Elisa V. Bandera, Christopher Haiman, Andrew Olshan, Julie Palmer, Christine Ambrosone, Song Yao. Single variant and gene-based replication analysis of reproductive aging in African American women in the AMBER Consortium [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 226.

A survey of microRNA single nucleotide polymorphisms identifies novel breast cancer susceptibility loci in a case-control, population-based study of African-American women

BackgroundMicroRNAs (miRNAs) regulate gene expression and influence cancer. Primary transcripts of miRNAs (pri-miRNAs) are poorly annotated and little is known about the role of germline variation in miRNA genes and breast cancer (BC). We sought to identify germline miRNA variants associated with BC risk and tumor subtype among African-American (AA) women.MethodsUnder the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium, genotyping and imputed data from four studies on BC in AA women were combined into a final dataset containing 224,188 miRNA gene single nucleotide polymorphisms (SNPs) for 8350 women: 3663 cases and 4687 controls. The primary miRNA sequence was identified for 566 miRNA genes expressed in Encyclopedia of DNA Elements (ENCODE) Tier 1 cell types and human pancreatic islets. Association analysis was conducted using logistic regression for BC status overall and by tumor subtype.ResultsA novel BC signal was localized to an 8.6-kb region of 17q25.3 by four SNPs (rs9913477, rs1428882938, rs28585511, and rs7502931) and remained statistically significant after multiple test correction (odds ratio (OR) = 1.44, 95% confidence interval (CI) = 1.26–1.65; p = 3.15 × 10−7; false discovery rate (FDR) = 0.03). These SNPs reside in a genomic location that includes both the predicted primary transcript of the noncoding miRNA gene MIR3065 and the first intron of the gene for brain-specific angiogenesis inhibitor 1-associated protein 2 (BAIAP2). Furthermore, miRNA-associated SNPs on chromosomes 1p32.3, 5q32, and 3p25.1 were the strongest signals for hormone receptor, luminal versus basal-like, and HER2 enrichment status, respectively. A second phase of genotyping (1397 BC cases, 2418 controls) that included two SNPs in the 8.6-kb region was used for validation and meta-analysis. While neither rs4969239 nor rs9913477 was validated, when meta-analyzed with the original dataset their association with BC remained directionally consistent (OR = 1.29, 95% CI = 1.16–1.44 (p = 4.18 × 10–6) and OR = 1.33, 95% CI = 1.17–1.51 (p = 1.6 × 10–5), respectively).ConclusionGermline genetic variation indicates that MIR3065 may play an important role in BC development and heterogeneity among AA women. Further investigation to determine the potential functional effects of these SNPs is warranted. This study contributes to our understanding of BC risk in AA women and highlights the complexity in evaluating variation in gene-dense regions of the human genome.

Frequency of breast cancer subtypes among African American women in the AMBER consortium

BackgroundBreast cancer subtype can be classified using standard clinical markers (estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2)), supplemented with additional markers. However, automated biomarker scoring and classification schemes have not been standardized. The aim of this study was to optimize tumor classification using automated methods in order to describe subtype frequency in the African American Breast Cancer Epidemiology and Risk (AMBER) consortium.MethodsUsing immunohistochemistry (IHC), we quantified the expression of ER, PR, HER2, the proliferation marker Ki67, and two basal-like biomarkers, epidermal growth factor receptor (EGFR) and cytokeratin (CK)5/6, in 1381 invasive breast tumors from African American women. RNA-based (prediction analysis of microarray 50 (PAM50)) subtype, available for 574 (42%) cases, was used to optimize classification. Subtype frequency was calculated, and associations between subtype and tumor characteristics were estimated using logistic regression.ResultsRelative to ER, PR and HER2 from medical records, central IHC staining and the addition of Ki67 or combined tumor grade improved accuracy for classifying PAM50-based luminal subtypes. Few triple negative cases (< 2%) lacked EGFR and CK5/6 expression, thereby providing little improvement in accuracy for identifying basal-like tumors. Relative to luminal A subtype, all other subtypes had higher combined grade and were larger, and ER-/HER2+ tumors were more often lymph node positive and late stage tumors. The frequency of basal-like tumors was 31%, exceeded only slightly by luminal A tumors (37%).ConclusionsOur findings indicate that automated IHC-based classification produces tumor subtype frequencies approximating those from PAM50-based classification and highlight high frequency of basal-like and low frequency of luminal A breast cancer in a large study of African American women.

Biology and Etiology of Young-Onset Breast Cancers among Premenopausal African American Women: Results from the AMBER Consortium.

Background: African American (AA) women have higher incidence of aggressive, young-onset (<40 years) breast cancers. Young- and older-onset disease may have distinct tumor biologies and etiologies; however, studies investigating age differences among AA women have been rare and generally underpowered.Methods: We examined tumor characteristics and breast cancer risk factors associated with premenopausal young (<40) vs. older (≥40) AA women's breast cancer in the African American Breast Cancer Epidemiology and Risk Consortium (2,008 cases and 5,144 controls). Unconditional logistic regression models assessed heterogeneity of tumor biology and risk factor associations by age, overall, and by estrogen receptor status.Results: Premenopausal AA women <40 years had higher frequency of poorer-prognosis tumor characteristics compared with older women, including negative estrogen and progesterone receptor status, triple-negative subtype, higher grade, higher stage, and larger tumors. Adiposity (i.e., waist-to-hip ratio) and family history of breast cancer were more strongly associated with young-onset disease [case-control OR = 1.46, 95% confidence interval (CI) = 1.04-2.05; OR = 3.10, 95% CI = 2.08-4.63, respectively] compared with older-onset disease (OR = 1.11, 95% CI = 0.91-1.35; OR = 1.57, 95% CI = 1.26-1.94). Breastfeeding showed a slight inverse risk association among young women (OR = 0.70, 95% CI = 0.43-1.16). Oral contraceptive use was associated with increased risk regardless of age. Considering various cutoff points for young age (<40, <45, <50), age-related heterogeneity was greatest when <40 was used.Conclusions: Among premenopausal AA women, diagnosis before age 40 is associated with more aggressive breast tumor biology and some etiologic differences.Impact: Modifiable risk factors including breastfeeding, adiposity, and oral contraceptive use may be important targets for mitigating harms of young-onset breast cancer. Cancer Epidemiol Biomarkers Prev; 26(12); 1722-9. ©2017 AACR.

Abstract 5276: Risk factors for ductal carcinoma in situ of the breast in African American women

Abstract Introduction: The clinical significance of a ductal carcinoma in situ (DCIS) diagnosis is uncertain. While overall breast cancer mortality risk from DCIS is very low, a recent analysis showed that African American women diagnosed with DCIS were more than twice as likely to die from breast cancer as U.S. white women. Elucidation of risk factors for DCIS in African American women may provide opportunities for risk reduction. Methods: To assess the relation of reproductive, anthropometric, and other factors to risk of DCIS in African American women, we pooled data from three epidemiologic studies participating in the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium - the Black Women’s Health Study, the Carolina Breast Cancer Study, and the Women’s Circle of Health Study. These studies contributed 805 DCIS cases and 13,830 controls to the analysis. We used unconditional logistic regression models to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for risk of DCIS in relation to each risk factor of interest. Multivariable models were used to mutually adjust for risk factors as well as matching factors (age, study, geographic region, and questionnaire time period). We also compared results to associations observed for invasive breast cancer (n=3,765). Results: First degree family history of breast cancer was associated with an increased risk of DCIS (OR 1.62, 95% CI 1.32, 1.98). Oral contraceptive use within the past 10 years (vs. never) was also associated with increased risk (OR 1.31, 95% CI 1.01, 1.70), as was late age at first birth (≥25 years vs. &amp;lt;20 years) (OR 1.29, 95% CI 1.04, 1.61). Older age at menarche (≥15 years vs. &amp;lt;11 years) was associated with a reduced risk (OR 0.67, 95% CI 0.49, 0.92). Women with higher body mass index (BMI) in early adulthood (≥25 kg/m2 at ages 18 or 21) had a reduced risk of DCIS compared to those who had a BMI &amp;lt;20 kg/m2 in early adulthood (OR 0.71, 95% CI 0.56, 0.91), but there was no association for current BMI. In general, associations of risk factors for DCIS were similar in magnitude and direction to those for invasive breast cancer. However, high waist-to-hip ratio and absence of breastfeeding, two factors associated with increased risk of invasive breast cancer, and particularly with estrogen receptor negative breast cancer among African American women, were not associated with DCIS, either overall or by estrogen receptor status. Conclusions: Our findings suggest that most risk factors for invasive breast cancer are also risk factors for DCIS among African American women. However, two important modifiable risk factors for invasive breast cancer in this population, higher waist-to-hip ratio and absence of breastfeeding, do not appear to influence DCIS risk. Citation Format: Kimberly A. Bertrand, Traci N. Bethea, Lynn Rosenberg, Elisa V. Bandera, Melissa Troester, Thaer Khoury, Christine B. Ambrosone, Julie R. Palmer. Risk factors for ductal carcinoma in situ of the breast in African American women [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 5276. doi:10.1158/1538-7445.AM2017-5276

Demographic, lifestyle, and genetic determinants of circulating concentrations of 25-hydroxyvitamin D and vitamin D–binding protein in African American and European American women ,

Background: Vitamin D may have anticancer activities. The high prevalence of vitamin D deficiency in African Americans (AAs) may be a contributing factor to the cancer health disparities between AAs and European Americans (EAs).Objectives: We compared concentrations of 25(OH)D and vitamin D-binding protein (VDBP) in AA and EA women and investigated determinants of the vitamin D-biomarker concentrations in both populations.Design: We used data and biospecimens from 909 AA and 847 EA healthy control subjects from the Carolina Breast Cancer Study (CBCS) and the Women's Circle of Health Study (WCHS) in the African American Breast Cancer Epidemiology and Risk Consortium. We measured plasma 25(OH)D and VDBP concentrations in all participants and genotyped 67 vitamin D-related genes in AA women only.Results: AA women had lower 25(OH)D concentrations than did EA women (mean ± SD: 14.2 ± 8.1 compared with 21.1 ± 11.5 ng/mL, respectively; P < 0.0001) but similar concentrations of VDBP (mean ± SD: 344 ± 133 compared with 336 ± 124 μg/mL, respectively; P = 0.25). With VDBP and other factors controlled for, the observed racial difference in 25(OH)D concentrations did not diminish. Relations of demographic and lifestyle factors with 25(OH)D were similar between AA and EA women. Although none of the genetic variants that have been identified in previous genome-wide association studies of 25(OH)D concentrations in EAs were significant (P > 0.05) in AAs, AA women who carried the allele of a functional single nucleotide polymorphism rs4988235, which has been previously associated with lactase expression and lactose tolerance, had higher dietary vitamin D intake and higher measured 25(OH)D concentrations.Conclusions: AA women have lower concentrations of total 25(OH)D than EA women do, but both groups have similar VDBP concentrations, suggesting that there are lower concentrations of free 25(OH)D in AAs. Although demographic and lifestyle determinants of 25(OH)D concentrations are similar between the 2 groups, genetic determinants may be ethnicity specific. Larger studies in AAs will be needed to fully elucidate the underlying determinants of low vitamin D concentrations in AA populations.

Alcohol Intake and Breast Cancer Risk in African American Women from the AMBER Consortium.

Background: Alcohol is a recognized risk factor for invasive breast cancer, but few studies involve African American women.Methods: The current analysis included 22,338 women (5,108 cases of invasive breast cancer) from the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium. The association between number of alcoholic drinks per week (dpw) and breast cancer was estimated using logistic regression, adjusting for potential confounders, and stratifying by breast cancer subtype.Results: Approximately 35% of controls were current drinkers at interview. Women who reported current drinking of ≥14 dpw had an elevated risk of breast cancer compared with light drinkers (>0-<4 dpw) [adjusted OR (ORadj), 1.33; 95% confidence interval (CI), 1.07-1.64]. We observed elevated risk among women drinking ≥7 dpw for ER - [ORadj, 1.31; 95% CI, 1.00-1.72], PR - [ORadj, 1.28; 95% CI, 1.00-1.63], HER2 - [ORadj, 1.36; 95% CI, 1.09-1.70], and triple-negative [ORadj, 1.39; 95% CI, 0.98-2.00] molecular subtype. Among receptor-positive cases, ORs remained elevated but attenuated relative to receptor-negative cases. Sensitivity analysis of age-defined windows of exposure (<30 years, 30-49, 50+ years of age) did not reveal variation in patterns of association. Risk associated with alcohol intake did not vary significantly by oral contraceptive use, smoking status, or menopausal status.Conclusions: Among African American women, similar to women of European descent, drinking ≥7 alcoholic dpw was associated with an increased risk of breast cancer regardless of subtype.Impact: Alcohol intake is a modifiable risk factor for breast cancer, and reduced intake among African American women should be encouraged. Cancer Epidemiol Biomarkers Prev; 26(5); 787-94. ©2017 AACR.

Trans-ethnic follow-up of breast cancer GWAS hits using the preferential linkage disequilibrium approach.

Leveraging population-distinct linkage equilibrium (LD) patterns, trans-ethnic follow-up of variants discovered from genome-wide association studies (GWAS) has proved to be useful in facilitating the identification of bona fide causal variants. We previously developed the preferential LD approach, a novel method that successfully identified causal variants driving the GWAS signals within European-descent populations even when the causal variants were only weakly linked with the GWAS-discovered variants. To evaluate the performance of our approach in a trans-ethnic setting, we applied it to follow up breast cancer GWAS hits identified mostly from populations of European ancestry in African Americans (AA). We evaluated 74 breast cancer GWAS variants in 8,315 AA women from the African American Breast Cancer Epidemiology and Risk (AMBER) consortium. Only 27% of them were associated with breast cancer risk at significance level α=0.05, suggesting race-specificity of the identified breast cancer risk loci. We followed up on those replicated GWAS hits in the AMBER consortium utilizing the preferential LD approach, to search for causal variants or better breast cancer markers from the 1000 Genomes variant catalog. Our approach identified stronger breast cancer markers for 80% of the GWAS hits with at least nominal breast cancer association, and in 81% of these cases, the marker identified was among the top 10 of all 1000 Genomes variants in the corresponding locus. The results support trans-ethnic application of the preferential LD approach in search for candidate causal variants, and may have implications for future genetic research of breast cancer in AA women.

Genetic variation in the insulin, insulin-like growth factor, growth hormone, and leptin pathways in relation to breast cancer in African-American women: the AMBER consortium.

The insulin/insulin-like growth factor (IGF) system and related pathways such as growth hormone, and leptin signaling have a key role in cancer development. It is unclear how germline variation in these pathways affects breast cancer risk. We conducted gene-based analyses of 184 genes in the insulin/IGF, growth hormone, and leptin pathways to identify genetic variation associated with risk of breast cancer overall, and for estrogen receptor (ER) subtypes. Tag single-nucleotide polymorphisms (SNPs) for each gene were selected and genotyped on a customized Illumina SNP array. Imputation was carried out using 1000 Genomes haplotypes. The analysis included 91,627 SNPs genotyped or imputed in 3,663 breast cancer cases, (1,983 ER-positive and 1,098 ER-negative) and 4,687 controls from the African American Breast Cancer Epidemiology and Risk consortium, a collaborative project of four large studies of breast cancer in African-American women (Carolina Breast Cancer Study, Black Women's Health Study, Women's Circle of Health Study, and Multiethnic Cohort). We used a multi-locus adaptive joint test to determine the association of each gene with overall breast cancer and ER subtypes. The most significant gene associations (P⩽0.01) were BAIAP2 and CALM2 for overall breast cancer; BAIAP2 and CSNK2A1 for ER+ breast cancer; and BRAF, BAD, and MAPK3 for ER− breast cancer. The association of BAD with ER− breast cancer was explained by a two-SNP risk model; all other associations were best explained by one-SNP risk models. In total, six genes and seven SNPs had suggestive associations with overall breast cancer or ER subtypes in African-American women.

Admixture Mapping of African-American Women in the AMBER Consortium Identifies New Loci for Breast Cancer and Estrogen-Receptor Subtypes.

Recent genetic admixture coupled with striking differences in incidence of estrogen receptor (ER) breast cancer subtypes, as well as severity, between women of African and European ancestry, provides an excellent rationale for performing admixture mapping in African American women with breast cancer risk. We performed the largest breast cancer admixture mapping study with in African American women to identify novel genomic regions associated with the disease. We conducted a genome-wide admixture scan using 2,624 autosomal ancestry informative markers (AIMs) in 3,629 breast cancer cases (including 1,968 ER-positive, 1093 ER-negative, and 601 triple-negative) and 4,658 controls from the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium, a collaborative study of four large geographically different epidemiological studies of breast cancer in African American women. We used an independent case-control study to test for SNP association in regions with genome-wide significant admixture signals. We found two novel genome-wide significant regions of excess African ancestry, 4p16.1 and 17q25.1, associated with ER-positive breast cancer. Two regions known to harbor breast cancer variants, 10q26 and 11q13, were also identified with excess of African ancestry. Fine-mapping of the identified genome-wide significant regions suggests the presence of significant genetic associations with ER-positive breast cancer in 4p16.1 and 11q13. In summary, we identified three novel genomic regions associated with breast cancer risk by ER status, suggesting that additional previously unidentified variants may contribute to the racial differences in breast cancer risk in the African American population.

Vigorous physical activity and risk of breast cancer in the African American breast cancer epidemiology and risk consortium.

The relationship between physical activity and breast cancer risk has been extensively studied among women of European descent, with most studies reporting inverse associations. However, data on American women of African ancestry (AA) and by tumor subtypes are sparse. Thus, we examined associations of vigorous exercise and breast cancer risk overall, and by estrogen receptor (ER) status, in the African American Breast Cancer Epidemiology and Risk Consortium. We pooled data from four large studies on 2482 ER+cases, 1374 ER- cases, and 16,959 controls. Multivariable logistic regression was used to compute odds ratios (OR) and 95% confidence intervals (CI) for the risk of breast cancer overall, and polytomous logistic regression was used to model the risk of ER+and ER- cancer. Recent vigorous exercise was associated with a statistically significant, modestly decreased risk for breast cancer overall (OR 0.88, 95% CI 0.81-0.96) and for ER+cancer (OR 0.88, 95% CI 0.80-0.98), but not for ER- cancer (OR 0.93, 95% CI 0.82-1.06). Overall, there was no strong evidence of effect modification by age, menopausal status, body mass index, and parity. However, our data were suggestive of modification by family history, such that an inverse association was present among women without a family history but not among those with a relative affected by breast cancer. Results from this large pooled analysis provide evidence that vigorous physical activity is associated with a modestly reduced risk of breast cancer in AA women, specifically ER+cancer.

Genetic variations in the Hippo signaling pathway and breast cancer risk in African American women in the AMBER Consortium.

The Hippo signaling pathway regulates cellular proliferation and survival, thus exerting profound effects on normal cell fate and tumorigenesis. Dysfunction of the Hippo pathway components has been linked with breast cancer stem cell regulation, as well as breast tumor progression and metastasis. TAZ, a key component of the Hippo pathway, is highly expressed in triple negative breast cancer; however, the associations of genetic variations in this important pathway with breast cancer risk remain largely unexplored. Here, we analyzed 8309 germline variants in 15 genes from the Hippo pathway with a total of 3663 cases and 4687 controls from the African American Breast Cancer Epidemiology and Risk Consortium. Odds ratios (ORs) were estimated using logistic regression for overall breast cancer, by estrogen receptor (ER) status (1983 ER positive and 1098 ER negative), and for case-only analyses by ER status. The Hippo signaling pathway was significantly associated with ER-negative breast cancer (pathway level P = 0.02). Gene-based analyses revealed that CDH1 was responsible for the pathway association (P < 0.01), with rs4783673 in CDH1 statistically significant after gene-level adjustment for multiple comparisons (P = 9.2×10(-5), corrected P = 0.02). rs142697907 in PTPN14 was associated with ER-positive breast cancer and rs2456773 in CDK1 with ER-negativity in case-only analysis after gene-level correction for multiple comparisons (corrected P < 0.05). In conclusion, common genetic variations in the Hippo signaling pathway may contribute to both ER-negative and ER+ breast cancer risk in AA women.

Abstract 814: Gene-based analysis of the IGF signaling pathway and risk of breast cancer in African American women: The AMBER consortium

Abstract Dysregulation of the IGF (insulin-like growth factor) signaling pathway plays a key role in cancer development. It is still unclear whether germline variation in genes in the IGF pathway may affect risk of breast cancer. We conducted a gene-based analysis of 184 genes in the IGF signaling pathway to identify genes carrying genetic variation affecting risk of breast cancer and the specific estrogen receptor (ER) subtypes. Tagging single nucleotide polymorphisms (SNPs) for each gene were selected and genotyped on a customized Illumina Exome Array. Imputation was carried out using 1000 Genomes haplotypes. The analysis included 91,627 SNPs in 3,663 breast cancer cases (including 1,983 ER positive,1,098 ER-negative) and 4,687 controls from the African American Breast Cancer Epidemiology and Risk (AMBER) consortium, a collaborative project of four large studies of breast cancer in African American women (Carolina Breast Cancer Study, Black Women's Health Study, Women's Circle of Health Study, and Multiethnic Cohort). We used a multi-locus adaptive joint (AdaJoint) test to determine the association of each gene in the IGF signaling pathway with overall breast cancer and ER subtypes. None of the 184 tested genes, including IGF, IGF binding protein (IGFBP), and IGF receptor (IGFR) genes were associated with disease after adjustment for multiple testing. At the nominal level of P≤0.01, BAIAP2 (P = 0.003), and CALM2 (P = 0.009) genes were associated with overall breast cancer; BAIAP2 (P = 0.001), and CSNK2A1 (P = 0.01) with ER+ breast cancer; and BRAF (P = 0.003), BAD (P = 0.005), and MAPK3 (P = 0.009) with ER- breast cancer. The intronic rs9913477 SNP in the BAIPA2 gene was significantly associated with overall (P = 3.2×10−7) and ER+ (P = 4.4×10−7) breast cancer at the pathway-wide level after adjusting for the total number of tested SNPs. Odds ratios and 95% confidence intervals of the risk G-allele were 1.44 (1.25, 1.66), and 1.53 (1.30, 1.81) for overall and ER+ breast cancer, respectively. BAIAP2 codes an adaptor protein, IRSp53, which functions as a substrate of the insulin receptor and IGF-1 receptor tyrosine kinases and links Rho-family small GTPases such as Rac. In vitro studies have shown that activation of Rac promotes metastatic behavior of breast cancer cells. In conclusion, we identified a SNP in BAIAP2 associated with overall and ER+ breast cancer. These results highlight the importance of the IGF signaling pathway in the pathogenesis of breast cancer. Citation Format: Edward A. Ruiz-Narvaez, Kathryn L. Lunetta, Chi-Chen Hong, Stephen A. Haddad, Song Yao, Ting-Yuan D. Cheng, Jeannette T. Bensen, Elisa V. Bandera, Christopher A. Haiman, Andrew F. Olshan, Christine B. Ambrosone, Lynn Rosenberg, Julie R. Palmer. Gene-based analysis of the IGF signaling pathway and risk of breast cancer in African American women: The AMBER consortium. [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 814.

An exome-wide analysis of low frequency and rare variants in relation to risk of breast cancer in African American Women: the AMBER Consortium.

A large percentage of breast cancer heritability remains unaccounted for, and most of the known susceptibility loci have been established in European and Asian populations. Rare variants may contribute to the unexplained heritability of this disease, including in women of African ancestry (AA). We conducted an exome-wide analysis of rare variants in relation to risk of overall and subtype-specific breast cancer in the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium, which includes data from four large studies of AA women. Genotyping on the Illumina Human Exome Beadchip yielded data for 170 812 SNPs and 8287 subjects: 3629 cases (1093 estrogen receptor negative (ER-), 1968 ER+, 568 ER unknown) and 4658 controls, the largest exome chip study to date for AA breast cancer. Pooled gene-based association analyses were performed using the unified optimal sequence kernel association test (SKAT-O) for variants with minor allele frequency (MAF) ≤ 5%. In addition, each variant with MAF >0.5% was tested for association using logistic regression. There were no significant associations with overall breast cancer. However, a novel gene, FBXL22 (P = 8.2×10(-6)), and a gene previously identified in GWAS of European ancestry populations, PDE4D (P = 1.2×10(-6)), were significantly associated with ER- breast cancer after correction for multiple testing. Cases with the associated rare variants were also negative for progesterone and human epidermal growth factor receptors-thus, triple-negative cancer. Replication is required to confirm these gene-level associations, which are based on very small counts at extremely rare SNPs.

Abstract C49: Relation of family history of cancer to risk of ER+, ER-, and triple-negative breast cancer in African American women

Abstract Introduction: Family history of breast cancer has been shown to be a strong risk factor for breast cancer in all populations studied. However, there are limited data related to risk of estrogen receptor negative (ER-) breast cancer in African American women, who have a disproportionately high incidence of ER- and triple negative (ER-, progesterone receptor negative, and HER2 receptor negative; TN) breast cancer. Even less information is available on whether a family history of other cancers also affects risk of ER- and TN breast cancer. Methods: Questionnaire data from the Black Women's Health Study, the Carolina Breast Cancer Study, the Multiethnic Cohort Study, and the Women's Circle of Health Study were pooled as part of the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium. Breast cancer cases were classified as ER+, ER-, and TN based on pathology data from medical records and/or state cancer registries. Participants were asked about first degree relatives with a breast cancer diagnosis and the age at which the relative was diagnosed. Participants were also asked about first degree relatives with prostate, lung, colorectal, ovarian, or cervical cancer or with lymphoma or leukemia. Polytomous logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for various categories of positive family history relative to no first degree relative with breast cancer or no first degree relative with any of the cancers. Multivariable analyses controlled for age, study, time period, and other potential confounders. Results: The analysis included 3,023 African American women with ER+, 1,497 with ER-, and 696 with TN breast cancer and 17,420 controls. First degree family history of breast cancer, regardless of whether first degree relatives had cancers other than breast cancer, was associated with a 70% increased risk of ER+, ER- and TN breast cancer; the ORs were 1.7 (95% CI 1.6-2.0) for ER+, 1.7 (95% CI 1.4-1.9) for ER-, and 1.7 (95% CI 1.4-2.1) for TN breast cancer. The ORs were somewhat higher if the relative was diagnosed before age 50 (2.0 for ER+, 1.9 for ER-, and 1.8 for TN). Among the six other cancer sites examined, only family history of cervical cancer was significantly associated with risk; the ORs were 2.4 (1.4-4.2) for ER- and 2.9 (1.5-5.5) for TN breast cancer and there was no association with ER+ breast cancer. The OR for family history of ovarian cancer in relation to TN breast cancer was 1.6 (0.9-2.7), which is of interest because findings from The Cancer Genome Atlas (TCGA) indicate that serous ovarian cancers and basal-like breast cancers, which are mostly triple negative, have many molecular commonalities. The ORs for a family history of both breast and prostate cancer versus no family history of any of the cancers were 3.4 (2.4-4.7) for ER+ cancer, as compared with 1.6 for breast alone (p-interaction=0.01), and 2.1 (1.2-3.7) for ER- cancer, as compared with 1.5 for breast alone (p-interaction=0.08). The OR for a family history of both breast and lung cancer was 3.3 (1.9-5.9) for TN breast cancer, compared to 1.5 for breast alone (p-interaction=0.10). The ORs for family history of breast plus two other cancers were 2.4 (1.6-3.6) for ER+, 2.8 (1.6-4.7) for ER-, and 2.7 (1.3-5.7) for TN breast cancer. Conclusion: Our results confirm that having a first degree family history of breast cancer is a strong risk factor for ER+, ER-, and TN breast cancer. The findings also suggest that having relatives with other cancers in addition to a relative with breast cancer may further increase risk. Consideration of family history of other cancers may improve risk prediction models. The association observed for family history of cervical cancer and increased risk of ER- and TN breast cancer was unexpected and needs to be replicated by other studies. Citation Format: Traci N. Bethea, Lynn Rosenberg, Nelsy Castro-Webb, Kathryn L. Lunetta, Lara E. Sucheston, Edward A. Ruiz-Narvaez, Marjory Charlot, Song Y. Park, Elisa V. Bandera, Melissa A. Troester, Christine B. Ambrosone, Julie R. Palmer. Relation of family history of cancer to risk of ER+, ER-, and triple-negative breast cancer in African American women. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr C49.

Abstract A77: Walking and vigorous exercise and risk of breast cancer in African American women

Abstract The relationship between physical activity and breast cancer risk has been extensively studied among women of European descent, with most studies reporting an inverse association. However, data on African American (AA) women and by tumor subtypes are sparse. Thus, we examined associations of vigorous exercise and walking for exercise and breast cancer risk overall and by estrogen receptor (ER) status in the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium. We pooled data on AA women from four large studies, the Black Women's Health Study, Carolina Breast Cancer Study, Multiethnic Cohort Study and Women's Circle of Health Study, for 2,482 ER+ cases, 1,374 ER- cases and 16,959 controls. Multivariable logistic regression was used to compute odds ratios (OR) and 95% confidence intervals (CI) for the risk of overall breast cancer, and polytomous logistic regression was used to model the risk of ER+ and ER- cancer. Based on all four studies, for recent vigorous exercise (reported by 29% of controls), the OR was 0.88 (95% CI: 0.81-0.96) for breast cancer overall, 0.88 (95% CI: 0.80-0.98) for ER+ breast cancer and 0.93 (95% CI: 0.82-1.06) for ER- breast cancer. There was a statistically significant trend across hours per week of vigorous activity for breast cancer overall (p for trend=0.006) and for ER+ cancer (p for trend=0.02), but there was not a clear dose response relationship, with the strongest reduced risk in the 1-2 and 3-4 hours/week categories. Data on walking for exercise, as the most frequently reported activity among adults who meet guidelines for regular physical activity (53% in controls), was available from two studies. Any walking for exercise was associated with reduced risk of breast cancer overall (OR=0.88, 95% CI: 0.80-0.97) and ER+ cancer (OR=0.87, 95% CI: 0.77-0.98), but not ER- cancer (OR=0.95, 95 CI: 0.81-1.12). There was a significant trend across hours per week of walking for breast cancer overall (p for trend=0.008) and ER+ breast cancer (p for trend=0.02), with the strongest reduced risk in the 5+ hours/week category. Our results from this large pooling study of AA women provide evidence that vigorous exercise and walking for exercise are associated with reduced risk of breast cancer, specifically ER+ cancer. Citation Format: zhihong Gong, Chi-Chen Hong, Elisa Bandera, Lucile Adams-Campbell, Song-Yi Park, Gary Zirpoli, Andrew Olshan, Christine Ambrosone, Julie Palmer, Lynn Rosenberg. Walking and vigorous exercise and risk of breast cancer in African American women. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr A77.