Mammary gland tissue changes appearance and functionality in different sequential steps. The tissue of virgin, pregnant, or lactating mammary glands changes controlled by finely regulated physiological processes. A fourth stage involutiontriggered upon weaning, involves remodeling, and the gland regresses to resemble a prepregnant stage.
Donald Earl Henson, Robert E. It truly is a remarkable event when traditional pathologic observations lead to new ideas about the prevention of cancer. In this issue of the JournalMilanese et al.
Background: All women have an immediate period of increased risk for developing breast cancer after childbirth, regardless of their age. Among women who have children at a relatively young age, pregnancy does eventually provide long term protection against breast cancer. However, older first-time mothers have a lifelong elevated risk for breast cancer.
Postpartum breast cancers are about three times more likely to spread and give rise to life-threatening metastatic tumors than those in women the same age who have not given birth. The new findings, based on a mouse model of breast cancer, represent an important step in considering ibuprofen as a cancer prevention agent in young women after pregnancy, according to researchers at OHSU in Portland, Oregon. Figure: A graphical summary from Pennock et al.
Women with dense breasts and no lobular involution were at a higher risk for developing breast cancer than those with non-dense breasts and complete involution, according to a study published online in The Journal of the National Cancer Institute. Apart from age, family history, and age at menarche, two additional factors associated with breast cancer risk include mammographic breast density and extent of lobular involution. Lobular involution is the physiological atrophy of the breast epithelium and is known to increase with increasing age.
Postlactational involution is the process following weaning during which the mammary gland undergoes massive cell death and tissue remodeling as it returns to the pre-pregnant state. Lobular involution is the process by which the breast epithelial tissue is gradually lost with aging of the mammary gland. While postlactational involution and lobular involution are distinct processes, recent studies have indicated that both are related to breast cancer development.
As most women get older, and especially after menopause, the milk-producing glands lobules shut down -- a process known as lobular regression, or involution. Since breast cancer is thought to originate in the lobules, their reduced size and number decreases the chance of cancer formation. Women who experience complete involution have half the risk of developing breast cancer of those who do not.
We hypothesized that gene expression related to abrupt mammary gland involution after forced weaning may be enriched in the tissues of IBC patients and, if so, provide a potential correlation between limited breast-feeding and the development of aggressive breast cancer. We utilized the Short Time-series Expression Miner STEM program to cluster significant signatures from two independent studies that analyzed gene expression at multiple time-points of mouse mammary gland involution. Examining the combined data, we identified 10 involution gene clusters Inv that share time-dependent regulation after forced weaning. Eight genes in Inv5 are upregulated in both the training and validation sets in IBC.