Female sex hormones estrogen and progesterone increase the number of mammary gland stem cells in mice, despite the fact that these cells do not have estrogen receptors, Australian researchers report in the journal Nature. In their opinion, this may be a reason for an increased risk of pregnancy-related breast cancer.
Estrogen and progesterone, steroid hormones produced by the ovaries, increase the risk of breast cancer, but the cellular mechanisms responsible for this risk are not yet known.
Jane Visvader and colleagues from The Walter and Eliza Hall Institute of Medical Research in Melbourne showed that the size of the population of mammary gland stem cells in mice is regulated by steroid hormones. Both hormones increase the number of stem cells, and the removal of ovaries or the use of an estrogen synthesis inhibitor impairs the ability of stem cells to constantly renew their population.
The authors observed that pregnancy leads to an increase in the number of mammary stem cells, which they believe may result in the duplication of abnormal cells carrying the mutation and the development of breast cancer. (PAP)