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容易被诊断为 雌激素受体阴性（ER-）乳腺癌，预后较差，死亡率较高。了解 AA妇女ER-乳腺癌的生物学机制和开发有效的预防措施 战略是一项尚未得到满足的关键需求，对公共卫生具有重大影响。我们和其他人已经证明 ER-乳腺癌的风险增加AA妇女谁是parous和不母乳喂养;因素 这在AA女性中更常见，可能有助于解释她们更高的ER肿瘤发病率。我们 假设特定生殖暴露导致前腔分化的表观遗传沉默 基因通过DNA甲基化，导致异常的，成熟停滞的管腔祖细胞的扩增， 这可能会导致ER癌症。我们以前的数据显示肿瘤DNA甲基化的明显差异 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FOXA 1，它促进管腔 - 通过正向调节祖细胞中的管腔基因表达特征来进行细胞分化， 抑制基底细胞表型。该基因在来自AA的ER-与ER+肿瘤中高度甲基化 妇女，特别是那些经产和不母乳喂养的妇女。与抑制作用一致 FOXA 1蛋白水平在ER-与ER+乳腺肿瘤中较低， 在ER中-来自经产与未经产妇女的肿瘤。支持这一假设，我们最近表明， 小鼠乳腺中Foxa 1的杂合缺失导致上皮细胞的显著偏斜 向管腔祖细胞的方向发展。在这些初步结果的基础上，我们提出了一个全面的 对来自1,621名AA乳腺癌妇女的肿瘤样本进行全基因组DNA甲基化分析， 黑人妇女健康研究）和妇女健康研究圈使用Illumina EPIC 850 K阵列。 将这些图谱与甲基化插补后来自383例AA病例的现有450 K数据相结合，我们将 检查FOXA 1和区分ER亚组的差异甲基化位点（DMLs）。随着流行病学 从这2,004例AA病例的数据中，我们将评估生殖风险因素与 使用加权基因相关网络分析和结构方程， 建模来评估复杂的关系。我们将评估平价之间的相同关系， 健康AA志愿者捐赠给科门组织的正常乳腺组织中的母乳喂养和甲基化 银行使用小鼠模型，我们将通过实验研究产次和母乳喂养是否会影响 Foxa 1和其他前腔候选基因的甲基化水平，以及不同的 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女性中侵袭性乳腺癌的病因，促进新标志物的开发 为那些处于最高风险的人，并为精确预防方法发现有希望的分子靶点。

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.