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 (AA) 女性比其他美国群体更有可能被诊断出患有 雌激素受体阴性（ER-）乳腺癌的预后较差，死亡率较高。了解 AA 女性 ER-乳腺癌的生物学机制和开发有效的预防措施 战略代表了一个未满足的关键需求，对公共卫生产生重大影响。我们和其他人已经表明 已生育且不进行母乳喂养的 AA 女性患 ER-乳腺癌的风险增加；因素 这在 AA 女性中更为常见，可能有助于解释她们 ER 肿瘤发病率较高的原因。我们 假设特定的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。我们之前的数据显示肿瘤 DNA 甲基化存在明显差异 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，它促进管腔 通过正向调节祖细胞中的管腔基因表达特征来实现细胞分化， 抑制基底细胞表型。与 AA 的 ER 肿瘤相比，该基因在 ER 肿瘤中高度甲基化 女性，尤其是那些已生育且未进行母乳喂养的女性。与抑制作用一致 甲基化对基因表达的影响，ER-乳腺肿瘤与 ER 乳腺肿瘤中的 FOXA1 蛋白水平较低，并且 经产妇与未产妇的 ER-肿瘤。为了支持这一假设，我们最近表明 小鼠乳腺中 Foxa1 的杂合缺失导致上皮细胞的显着倾斜 群体走向管腔祖细胞。基于这些初步结果，我们提出了一项全面的 对 1,621 名患有乳腺癌的 AA 女性的肿瘤样本进行全基因组 DNA 甲基化分析 黑人女性健康研究）和女性健康圈研究使用 IIllumina EPIC 850K 阵列。 将这些概况与甲基化插补后来自 383 个 AA 病例的现有 450K 数据相结合，我们将 检查 FOXA1 和区分 ER 亚组的差异甲基化位点 (DML)。具有流行病学 根据这 2,004 个 AA 病例的数据，我们将评估生殖风险因素与 FOXA1 和顶级 DML 的甲基化，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。我们将评估奇偶性之间的相同关系， 健康 AA 志愿者向 Komen 组织捐赠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胎次和母乳喂养是否会影响 Foxa1 和其他前腔候选基因的甲基化水平，以及不同的相对比例 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，促进新标志物的开发 针对那些风险最高的人，并发现有希望的分子目标，以实现精准的预防方法。

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.