Parity reduces mammary repopulating activity but does not affect mammary stem cells defined as CD24 + CD29/CD49fhi in mice.
Abstract
Breast cancer (BCa) mortality is decreasing with early detection and improvement in therapies. The incidence of BCa, however, continues to increase, particularly estrogen-receptor-positive (ER +) subtypes. One of the greatest modifiers of ER + BCa risk is childbearing (parity), with BCa risk halved in young multiparous mothers. Despite convincing epidemiological data, the biology that underpins this protection remains unclear. Parity-induced protection has been postulated to be due to a decrease in mammary stem cells (MaSCs); however, reports to date have provided conflicting data. We have completed rigorous functional testing of repopulating activity in parous mice using unfractionated and MaSC (CD24midCD49fhi)-enriched populations. We also developed a novel serial transplant method to enable us to assess self-renewal of MaSC following pregnancy. Lastly, as each pregnancy confers additional BCa protection, we subjected mice to multiple rounds of pregnancy to assess whether additional pregnancies impact MaSC activity. Here, we report that while repopulating activity in the mammary gland is reduced by parity in the unfractionated gland, it is not due to a loss in the classically defined MaSC (CD24+CD49fhi) numbers or function. S...Continue Reading
References
Citations
Desensitization of human breast progenitors by a transient exposure to pregnancy levels of estrogen.
Related Concepts
Related Feeds
Breast Cancer: Chemo-Resistance
Some cancers are difficult to treat and aggressive including the "triple-negative" breast cancer. This type of cancer is chemoresistant even before chemotherapy begins. Here are the latest discoveries chemo-resistance in breast cancer.