African American Breast Cancer Epidemiology And Risk 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.

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.

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

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.

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.

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 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.

Performance of Three-Biomarker Immunohistochemistry for Intrinsic Breast Cancer Subtyping in the AMBER Consortium.

Classification of breast cancer into intrinsic subtypes has clinical and epidemiologic importance. To examine accuracy of IHC-based methods for identifying intrinsic subtypes, a three-biomarker IHC panel was compared with the clinical record and RNA-based intrinsic (PAM50) subtypes. Automated scoring of estrogen receptor (ER), progesterone receptor (PR), and HER2 was performed on IHC-stained tissue microarrays comprising 1,920 cases from the African American Breast Cancer Epidemiology and Risk (AMBER) consortium. Multiple cores (1-6/case) were collapsed to classify cases, and automated scoring was compared with the clinical record and to RNA-based subtyping. Automated analysis of the three-biomarker IHC panel produced high agreement with the clinical record (93% for ER and HER2, and 88% for PR). Cases with low tumor cellularity and smaller core size had reduced agreement with the clinical record. IHC-based definitions had high agreement with the clinical record regardless of hormone receptor positivity threshold (1% vs. 10%), but a 10% threshold produced highest agreement with RNA-based intrinsic subtypes. Using a 10% threshold, IHC-based definitions identified the basal-like intrinsic subtype with high sensitivity (86%), although sensitivity was lower for luminal A, luminal B, and HER2-enriched subtypes (76%, 40%, and 37%, respectively). Three-biomarker IHC-based subtyping has reasonable accuracy for distinguishing basal-like from nonbasal-like, although additional biomarkers are required for accurate classification of luminal A, luminal B, and HER2-enriched cancers. Epidemiologic studies relying on three-biomarker IHC status for subtype classification should use caution when distinguishing luminal A from luminal B and when interpreting findings for HER2-enriched cancers.

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.

Genetic variations in vitamin D-related pathways and breast cancer risk in African American women in the AMBER consortium.

Studies of genetic variations in vitamin D-related pathways and breast cancer risk have been conducted mostly in populations of European ancestry, and only sparsely in African Americans (AA), who are known for a high prevalence of vitamin D deficiency. We analyzed 24,445 germline variants in 63 genes from vitamin D-related pathways in the African American Breast Cancer Epidemiology and Risk (AMBER) consortium, including 3,663 breast cancer cases and 4,687 controls. Odds ratios (OR) were derived from logistic regression models for overall breast cancer, by estrogen receptor (ER) status (1,983 ER positive and 1,098 ER negative), and for case-only analyses of ER status. None of the three vitamin D-related pathways were associated with breast cancer risk overall or by ER status. Gene-level analyses identified associations with risk for several genes at a nominal p ≤ 0.05, particularly for ER- breast cancer, including rs4647707 in DDB2. In case-only analyses, vitamin D metabolism and signaling pathways were associated with ER- cancer (pathway-level p = 0.02), driven by a single gene CASR (gene-level p = 0.001). The top SNP in CASR was rs112594756 (p = 7 × 10(-5), gene-wide corrected p = 0.01), followed by a second signal from a nearby SNP rs6799828 (p = 1 × 10(-4), corrected p = 0.03). In summary, several variants in vitamin D pathways were associated with breast cancer risk in AA women. In addition, CASR may be related to tumor ER status, supporting a role of vitamin D or calcium in modifying breast cancer phenotypes.

Hormone-related pathways and risk of breast cancer subtypes in African American women.

We sought to investigate genetic variation in hormone pathways in relation to risk of overall and subtype-specific breast cancer in women of African ancestry (AA). Genotyping and imputation yielded data on 143,934 SNPs in 308 hormone-related genes for 3663 breast cancer cases (1098 ER-, 1983 ER+, 582 ER unknown) and 4687 controls from the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium. AMBER includes data from four large studies of AA women: the Carolina Breast Cancer Study, the Women's Circle of Health Study, the Black Women's Health Study, and the Multiethnic Cohort Study. Pathway- and gene-based analyses were conducted, and single-SNP tests were run for the top genes. There were no strong associations at the pathway level. The most significantly associated genes were GHRH, CALM2, CETP, and AKR1C1 for overall breast cancer (gene-based nominal p≤0.01); NR0B1, IGF2R, CALM2, CYP1B1, and GRB2 for ER+ breast cancer (p≤0.02); and PGR, MAPK3, MAP3K1, and LHCGR for ER- disease (p≤0.02). Single-SNP tests for SNPs with pairwise linkage disequilibrium r (2)<0.8 in the top genes identified 12 common SNPs (in CALM2, CETP, NR0B1, IGF2R, CYP1B1, PGR, MAPK3, and MAP3K1) associated with overall or subtype-specific breast cancer after gene-level correction for multiple testing. Rs11571215 in PGR (progesterone receptor) was the SNP most strongly associated with ER- disease. We identified eight genes in hormone pathways that contain common variants associated with breast cancer in AA women after gene-level correction for multiple testing.

Abstract PR10: Menopausal female hormone use in relation to risk of estrogen receptor positive and estrogen receptor negative breast cancer in African American women: Findings from the AMBER consortium

Abstract Background: Previous studies, mostly of white women, have found that female hormone supplements, particularly medications that combine estrogen with progestin, are associated with an increased risk of breast cancer. We examined the use of estrogen alone and estrogen combined with progestin in relation to risk of estrogen receptor-positive (ER+) and ER-negative (ER-) breast cancer in a large combined analysis of data from African American women. Methods: Questionnaire data from two cohort (Black Women's Health Study, Multiethnic Cohort Study) and two case-control (Carolina Breast Cancer Study, Women's Circle of Health Study) studies of breast cancer in African American women were harmonized as part of the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium. Female hormone use was examined among post-menopausal women age 40 and older. ER+ (n=1,486) and ER- (n=638) cases were compared with 8,425 controls. Odds ratios (OR) and 95% confidence intervals (CI) were estimated in polytomous logistic regression analysis with adjustment for study, age, year, geographic region, education, age at menopause, type of menopause, body mass index, oral contraceptive use, family history of breast cancer, parity, age at first birth, alcohol use, and smoking. Results: 37% of women had ever used estrogen alone and 17% had ever used estrogen plus progestin. Use of estrogen plus progestin, relative to never use, was associated with increased risk of ER+ breast cancer (OR=1.43, 95% CI 1.22-1.68). ORs were highest for long duration use (10+ years) and for recent use. The positive associations were also stronger in women with body mass index less than 25 and women age 60 and older. Length of time between menopause and initiation of hormone therapy did not modify the association. By contrast, use of estrogen alone was not associated with ER+ cancer (OR=1.02, 95% CI 0.88-1.17). There were no significant associations of estrogen alone or estrogen plus progestin with ER- breast cancer. Conclusions: Use of combination menopausal hormone supplements was associated with increased risk of ER+, but not ER-, breast cancer among African American women. These results are consistent with findings from studies of white women. This abstract was also presented as Poster B42. Citation Format: Emma Viscidi, Lynn Rosenberg, Chi-Chen Hong, Melissa A. Troester, Elisa V. Bandera, Christopher A. Haiman, Laurence N. Kolonel, Andrew F. Olshan, Christine B. Ambrosone, Julie R. Palmer. Menopausal female hormone use in relation to risk of estrogen receptor positive and estrogen receptor negative breast cancer in African American women: Findings from the AMBER consortium. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr PR10.

Abstract B21: Intratumoral hormone receptor heterogeneity is a characteristic of high-grade breast cancer and is associated with inter-laboratory hormone receptor status discordance

Abstract Introduction: Intratumoral hormone receptor (HR) heterogeneity may have implications for molecular classification of breast tumors which, in turn, may impact clinical decision making and epidemiologic research. Prior studies show that 10-20% of patients have discordant estrogen receptor (ER) or progesterone receptor (PR) status upon repeat assay. While technical factors contribute to this discordance, intratumoral HR heterogeneity may also play a role. We examined the association between intratumoral HR heterogeneity, measured at a single research laboratory, and clinical HR status, tumor characteristics and demographic variables. Methods: We used paraffin-embedded blocks from 932 invasive breast cancer cases, of which 497 were African-American, from the population-based Carolina Breast Cancer Study Phase 3, part of the African-American Breast Cancer Epidemiology and Risk (AMBER) Consortium. Two to four 1mm tumor cores per case were assembled into tissue microarrays and stained for ER and PR at a single research laboratory. ER and PR status (positive: ≥1% positive tumor cells; negative: &amp;lt;1%) were assigned to each core by automated digital image analysis and ER and PR status were assigned to each case by core-to-case collapsing, using the weighted average of positive cells across all cores. Intratumoral heterogeneity status (i.e. ‘homogeneous’ vs. ‘heterogeneous’) was assigned based on ‘identical’ or ‘different’ HR status between cores from a single case. Multivariable logistic regression was used to evaluate the association between heterogeneity status and patient and tumor characteristics, overall and stratified by menopausal status. Clinical HR status (positive vs. negative) was abstracted from medical records and concordance between clinical and research ER and PR status were examined, overall and stratified by heterogeneity status. Results: Of 932 cases, 95 (10%) had ER heterogeneity while 149 (16%) had PR heterogeneity. Overall, there was high agreement between clinical and research ER status (93% concordance; 95% confidence interval (CI) 92-95%) and PR status (89%; 95%CI 87-91%), consistent with previously reported inter-laboratory concordance rates. However, agreement was lower in cases with intratumoral heterogeneity (ER: 74%; 95%CI 65-83% and PR: 61%; 95%CI 53-69%), relative to homogeneous cases (ER: 96%; 95%CI 95-97% and PR: 94%; 95%CI 92-96%). Obesity, defined as BMI≥30kg/m2, was associated with increased odds of ER heterogeneity (adjusted odds ratio (OR)obese vs. normal weight 1.76; 95%CI 0.95-3.29), with a stronger association among postmenopausal women (OR 2.52; 95%CI 1.14-5.56). High tumor grade was associated with increased odds of both ER and PR heterogeneity (ORgrade III vs. I 3.14; 95%CI 1.47-6.70 and ORgrade III vs. I 2.28; 95%CI 1.26-4.14, respectively). There were no associations between intratumoral heterogeneity and age, race or menopausal status. Conclusions: Intratumoral heterogeneity may account for a portion of the well-documented inter-laboratory discordance in ER and PR status, with implications for tumor subtype classification. Intratumoral heterogeneity was more prevalent in high grade tumors, indicating that it may be a feature of aggressive breast cancer. Furthermore, obese postmenopausal women were more likely to have intratumoral ER heterogeneity, suggesting a potential mechanism underlying the association between obesity and worse breast cancer prognosis. Although these data do not support an association between intratumoral heterogeneity and race, given that both high grade disease and obesity are more common in African Americans, future studies should explore a possible role for intratumoral heterogeneity in breast cancer racial disparities. Citation Format: Emma H. Allott, Joseph Geradts, Xuezheng Sun, Stephanie M. Cohen, Thaer Khoury, Wiam Bshara, Gary Zirpoli, Julie R. Palmer, Christine B. Ambrosone, Andrew F. Olshan, Melissa A. Troester. Intratumoral hormone receptor heterogeneity is a characteristic of high-grade breast cancer and is associated with inter-laboratory hormone receptor status discordance. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr B21.

Abstract 1878: Dietary vitamin A intake and breast cancer risk among African American women: The AMBER Consortium

Abstract Introduction: Some studies in women of European descent showed an inverse association of dietary vitamin A intake with breast cancer risk, in particular, among premenopausal women. However, it is unknown whether the associations exist among women of African descent. Methods: In the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium, we included data from 2487 breast cancer cases and 11,843 controls from the three studies that had food frequency questionnaires (FFQs) (Black Women's Health Study [BWHS], Multiethnic Cohort Study [MEC], and Women's Circle of Health Study [WCHS]). Total vitamin A (preformed vitamin A from animal sources plus carotenoids from fruits and vegetable) intake in μg retinol equivalent (RE) from diet only was assessed by FFQ, and estrogen receptor (ER) status was abstracted from pathology reports. Logistic regression was performed to estimate odds ratios (OR) and 95% confidence intervals (CI) for study-specific quintiles adjusting for age, education, body mass index, study, time period, geographical region, family history of breast cancer, age at menarche, parity, age at first birth, use of hormone replacement therapy, duration of oral contraceptive use, smoking, alcohol use, and total energy intake. Results: We observed no association of dietary total vitamin A intake with ER-positive breast cancer overall. However, dietary total vitamin A intake was inversely associated with ER-positive breast cancer among premenopausal women (quintiles 5 vs. 1: OR = 0.66, 95% CI = 0.47-0.93; p-trend = 0.022), but not among postmenopausal women (quintiles 5 vs 1: OR 1.06, 95% CI 0.81-1.39; p-trend = 0.89). There was no evidence for an association of dietary total vitamin A intake with ER-negative breast cancer, regardless of menopausal status. Only BWHS and MEC had information on multivitamin supplement use; adjusting for this variable did not change the associations in these two studies. Conclusion: A higher versus lower consumption of total vitamin A from diet was associated with a lower risk of ER-positive breast cancer among premenopausal African American women. This finding is consistent with the observation in women of European decent; the potentially beneficial influence of vitamin A on ER-positive breast cancer warrants investigation. (Funding: NIH/NCI P01 CA151135) Citation Format: Ting-Yuan D. Cheng, Susan E. McCann, Gary Zirpoli, Song Yao, Elisa V. Bandera, Laurence N. Kolonel, Lynn Rosenberg, Andrew F. Olshan, Julie R. Palmer, Christine B. Ambrosone. Dietary vitamin A intake and breast cancer risk among African American women: The AMBER Consortium. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1878. doi:10.1158/1538-7445.AM2015-1878