Agurs-Collins Tanya, Ross Sharon A, Dunn Barbara K
Division of Cancer Control and Population Sciences, National Cancer Institute, Rockville, MD, United States.
Division of Cancer Prevention, National Cancer Institute, Rockville, MD, United States.
Front Oncol. 2019 Sep 4;9:765. doi: 10.3389/fonc.2019.00765. eCollection 2019.
Obesity is associated with increased risk of breast and other cancers. However, the complexity of the underlying mechanisms, together with the interplay of diet and physical activity-contributing to energy balance-and the role of adipose tissue, pose challenges to our understanding of the basis of this increased risk. Epidemiologic studies have documented a higher obesity prevalence in US black women compared to white women. Elucidation of the contribution of potential biological differences among racially distinct groups to their differences in breast cancer (BC) risk and mortality have been topics of considerable interest in recent years. The racial and ethnic variation in body fat distribution may account for at least part of the differences in breast cancer rates in these populations. Yet, while black women exhibit higher rates of obesity compared to white women, this does not translate directly into higher rates of BC. In fact, overall, BC in black women occurs with a lower incidence than BC in white women. Obesity is a known risk factor for postmenopausal breast cancer, and growing evidence suggests that abdominal obesity, also known as central obesity, may increase risk for triple negative breast cancer, which is more common in premenopausal women. The positive association of postmenopausal BC risk and specifically estrogen receptor (ER)-positive BC, is presumably due largely to accumulation of estrogen in the adipose tissue of the breast and other tissues. Of the two main types of adipose tissue-subcutaneous and visceral-visceral adipocytes are more active metabolically. Such adipose tissue harbors multiple molecular entities that promote carcinogenesis: endocrine molecules/hormones, immunologic factors, inflammatory cytokines, metabolic alterations, and other components of the microenvironment. Expression of these culpable entities is largely regulated by epigenetic mechanisms. The interrelationship between these entities and drivers of epigenetic alteration are critical to the regulation of pathways connecting obesity and cancer risk. Initiatives to counteract the carcinogenic effects of obesity have primarily involved modulation of energy balance by diet. However, targeting of specific molecular abnormalities characterizing adiposity offers an alternative approach to preventing cancer. Our goal in this review is to first discuss the major mechanisms contributing to the obesity-breast cancer link. We will also consider race, specifically black/white differences, as they relate to the association of obesity with breast cancer risk. Then we will enumerate strategies targeting these mechanisms to reduce BC risk, in large part by way of dietary interventions with potential to mitigate the cancer-promoting components of adiposity.
肥胖与乳腺癌及其他癌症风险增加相关。然而,潜在机制的复杂性,以及饮食和体育活动(它们共同影响能量平衡)与脂肪组织的作用之间的相互作用,给我们理解这种风险增加的基础带来了挑战。流行病学研究表明,与白人女性相比,美国黑人女性的肥胖患病率更高。近年来,阐明不同种族群体之间潜在的生物学差异对其乳腺癌(BC)风险和死亡率差异的影响一直是备受关注的话题。身体脂肪分布的种族和民族差异可能至少部分解释了这些人群中乳腺癌发病率的差异。然而,尽管黑人女性的肥胖率高于白人女性,但这并未直接转化为更高的乳腺癌发病率。事实上,总体而言,黑人女性患乳腺癌的发病率低于白人女性。肥胖是绝经后乳腺癌的已知风险因素,越来越多的证据表明,腹部肥胖(也称为中心性肥胖)可能会增加三阴性乳腺癌的风险,而三阴性乳腺癌在绝经前女性中更为常见。绝经后乳腺癌风险,特别是雌激素受体(ER)阳性乳腺癌的正相关,可能主要是由于雌激素在乳腺和其他组织的脂肪组织中积累。在两种主要类型的脂肪组织——皮下脂肪组织和内脏脂肪组织中,内脏脂肪细胞的代谢更活跃。这种脂肪组织含有多种促进致癌作用的分子实体:内分泌分子/激素、免疫因子、炎性细胞因子、代谢改变以及微环境的其他成分。这些罪魁祸首实体的表达在很大程度上受表观遗传机制调控。这些实体与表观遗传改变驱动因素之间的相互关系对于连接肥胖与癌症风险的途径的调控至关重要。对抗肥胖致癌作用的举措主要涉及通过饮食调节能量平衡。然而,针对肥胖所特有的特定分子异常采取措施提供了一种预防癌症的替代方法。我们在本综述中的目标是首先讨论导致肥胖与乳腺癌关联的主要机制。我们还将考虑种族,特别是黑人/白人差异,因为它们与肥胖与乳腺癌风险的关联有关。然后我们将列举针对这些机制以降低乳腺癌风险的策略,很大程度上是通过饮食干预,这些干预有可能减轻肥胖促进癌症的成分。