Relationships between parity, breastfeeding and ER- breast cancer in African American women: Elucidating the biologic underpinnings at the molecular and cellular level.

摘要：非裔美国人(AA)女性比其他美国群体更有可能被诊断为 雌激素受体阴性(ER-)乳腺癌，预后较差，死亡率高。了解 再生障碍性贫血妇女ER乳腺癌的生物学机制及有效预防 战略是一种严重的未得到满足的需求，具有重大的公共卫生影响。我们和其他人已经展示了 非母乳喂养的AA妇女患ER-乳腺癌的风险增加；因素 这在再障女性中更为常见，这可能有助于解释她们较高的ER肿瘤发病率。我们 假设特定生殖暴露导致腔前分化的表观遗传沉默 基因通过DNA甲基化，导致异常的、成熟受阻的腔前体细胞的扩张， 这可能会导致ER癌症。我们先前的数据显示在肿瘤DNA甲基化方面存在明显差异 根据ER状态。从这些数据中得出的一个强有力的候选基因是FOXA1，它促进鲁米那 正向调节祖细胞中腔基因表达信号的细胞分化 抑制基底细胞表型。该基因在再生障碍性贫血的ER-VS ER肿瘤中高度甲基化 妇女，特别是那些经产妇和非母乳喂养的妇女。与抑制作用相一致 在基因表达甲基化方面，FOXA1蛋白水平在ER-与ER-乳腺肿瘤中较低，且较低 来自临产妇女和未临产妇女的ER肿瘤。支持这一假设的是，我们最近证明 小鼠乳腺FOXA1杂合性缺失导致上皮细胞急剧倾斜 人口向着流明的祖细胞发展。在这些初步结果的基础上，我们提出了一个全面的 1621例AA女性乳腺癌患者的全基因组DNA甲基化分析 黑人妇女健康研究)和使用IIllumina EPIC 850K阵列的妇女健康圈研究。 结合这些图谱和甲基化后383例再生障碍性贫血病例的现有45万数据，我们将 检查区分ER亚组的FOXA1和差异甲基化基因座(DML)。与流行病学有关 来自这2,004个再生障碍性贫血病例的数据，我们将评估生殖风险因素和 用加权基因相关网络分析和结构方程研究FOXA1和TOP DMLS的甲基化 建模以评估复杂的关系。我们将评估产次之间的相同关系， 健康AA志愿者捐赠给Komen组织的正常乳房组织中的母乳喂养和甲基化 银行。利用小鼠模型，我们将通过实验研究产次和母乳喂养是否会影响 FOXA1和其他原癌候选基因的甲基化水平，以及不同基因的相对比例 乳腺上皮细胞群。这种跨学科、多管齐下的方法将使我们能够 了解AA女性侵袭性乳腺癌的病因，促进新标记物的开发 对于那些风险最高的人，并发现有希望的精确预防方法的分子靶点。

ABSTRACT: African-American (AA) women are more likely than other US groups to be diagnosed with estrogen receptor negative (ER-) breast cancer, with poorer prognosis and higher mortality. Understanding the biological mechanisms underlying ER- breast cancer in AA women and developing effective preventive strategies represents a critical unmet need with major public health implications. We and others have shown that risk of ER- breast cancer is increased among AA women who are parous and do not breastfeed; factors that are more common among AA women, and may help to explain their higher incidence of ER- tumors. We hypothesize that specific reproductive exposures result in epigenetic silencing of pro-luminal differentiation genes via DNA methylation, leading to an expansion of aberrant, maturation-arrested luminal progenitor cells, which can give rise to ER- cancers. Our previous data showed distinct differences in tumor DNA methylation according to ER status. One strong candidate gene derived from these data is FOXA1, which promotes luminal cell differentiation by positively regulating a luminal gene expression signature in progenitor cells and repressing the basal cell phenotype. This gene was hyper-methylated in ER- versus ER+ tumors from AA women, particularly in those who were parous and did not breastfeed. Consistent with inhibitory effects of methylation on gene expression, FOXA1 protein levels were lower in ER- versus ER+ breast tumors, and lower in ER- tumors from parous vs. nulliparous women. Supporting this hypothesis, we recently showed that heterozygous deletion of Foxa1 in the mouse mammary gland results in a dramatic skewing of epithelial cell populations toward luminal progenitors. Building on these preliminary results, we propose a comprehensive genome-wide DNA methylation analysis of tumor samples from 1,621 AA women with breast cancer from the Black Women's Health Study) and the Women's Circle of Health Study using the IIllumina EPIC 850K array. Combining these profiles with existing 450K data from 383 AA cases after methylation imputation, we will examine FOXA1 and differentially methylated loci (DMLs) that distinguish ER subgroups. With epidemiologic data from these 2,004 AA cases, we will assess associations between reproductive risk factors and methylation of FOXA1 and top DMLs, using weighted gene correlation network analysis and structural equation modeling to evaluate complex relationships. We will evaluate the same relationships between parity, breastfeeding and methylation in normal breast tissue donated by healthy AA volunteers to the Komen Tissue Bank. Using mouse models, we will experimentally investigate if parity and breastfeeding influence the methylation level of Foxa1 and other pro-luminal candidate genes, as well as relative proportions of distinct mammary gland epithelial cell populations. This transdisciplinary, multi-pronged approach will enable us to understand the etiology of aggressive breast cancer in AA women, facilitate the development of novel markers for those at highest risk, and uncover promising molecular targets for precision prevention approaches.