Department of Medical Imaging, Cancer Hospital of Dalian University of Technology, Liaoning Cancer Hospital & Institute, No.44 Xiaoheyan Road, Dadong District, Shenyang, 110042, China.
Department of Laboratory Medicine, Cancer Hospital of Dalian University of Technology, Liaoning Cancer Hospital & Institute, No.44 Xiaoheyan Road, Dadong District, Shenyang, 110042, China.
Int Breastfeed J. 2024 Sep 16;19(1):65. doi: 10.1186/s13006-024-00672-7.
Mammographic density has been associated with breast cancer risk, and is modulated by established breast cancer risk factors, such as reproductive and hormonal history, as well as lifestyle. Recent epidemiological and biological findings underscore the recognized benefits of breastfeeding in reducing breast cancer risk, especially for aggressive subtypes. Current research exploring the association among mammographic density, breastfeeding, and breast cancer is sparse.
Changes occur in the breasts during pregnancy in preparation for lactation, characterized by the proliferation of mammary gland tissues and the development of mammary alveoli. During lactation, the alveoli fill with milk, and subsequent weaning triggers the involution and remodeling of these tissues. Breastfeeding influences the breast microenvironment, potentially altering mammographic density. When breastfeeding is not initiated after birth, or is abruptly discontinued shortly after, the breast tissue undergoes forced and abrupt involution. Conversely, when breastfeeding is sustained over an extended period and concludes gradually, the breast tissue undergoes slow remodeling process known as gradual involution. Breast tissue undergoing abrupt involution displays denser stroma, altered collagen composition, heightened inflammation and proliferation, along with increased expression of estrogen receptor α (ERα) and progesterone receptor. Furthermore, elevated levels of pregnancy-associated plasma protein-A (PAPP-A) surpass those of its inhibitors during abrupt involution, enhancing insulin-like growth factor (IGF) signaling and collagen deposition. Prolactin and small molecules in breast milk may also modulate DNA methylation levels. Drawing insights from contemporary epidemiological and molecular biology studies, our review sheds light on how breastfeeding impacts mammographic density and explores its role in influencing breast cancer.
This review highlights a clear protective link between breastfeeding and reduced breast cancer risk via changes in mammographic density. Future research should investigate the effects of breastfeeding on mammographic density and breast cancer risk among various ethnic groups and elucidate the molecular mechanisms underlying these associations. Such comprehensive research will enhance our understanding and facilitate the development of targeted breast cancer prevention and treatment strategies.
乳腺密度与乳腺癌风险相关，并且受到乳腺癌风险因素的调节，如生殖和激素史以及生活方式。最近的流行病学和生物学发现强调了母乳喂养在降低乳腺癌风险方面的公认益处，特别是对于侵袭性亚型。目前，探索乳腺密度、母乳喂养和乳腺癌之间关联的研究还很匮乏。
怀孕期间乳房会发生变化，为泌乳做准备，特征是乳腺组织的增殖和乳腺腺泡的发育。在泌乳期间，腺泡充满乳汁，随后断奶会引发这些组织的退化和重塑。母乳喂养会影响乳房微环境，可能会改变乳腺密度。如果产后不开始母乳喂养，或者在产后不久突然中断母乳喂养，乳房组织会经历强制和突然的退化。相反，如果母乳喂养持续时间长且逐渐结束，乳房组织会经历缓慢的重塑过程，称为逐渐退化。经历突然退化的乳房组织显示出更密集的基质、改变的胶原组成、更高的炎症和增殖水平，以及雌激素受体α（ERα）和孕激素受体的表达增加。此外，在突然退化期间，妊娠相关血浆蛋白-A（PAPP-A）的水平升高超过其抑制剂，增强胰岛素样生长因子（IGF）信号和胶原沉积。母乳中的催乳素和小分子也可能调节 DNA 甲基化水平。通过借鉴当代流行病学和分子生物学研究的成果，我们的综述阐明了母乳喂养如何通过乳腺密度的变化来影响乳腺癌风险。
本综述强调了母乳喂养通过改变乳腺密度与降低乳腺癌风险之间的明确保护联系。未来的研究应调查母乳喂养对不同种族群体中乳腺密度和乳腺癌风险的影响，并阐明这些关联的分子机制。这种全面的研究将增进我们的理解，并有助于制定有针对性的乳腺癌预防和治疗策略。
