After 40 or so weeks of gestation, labor and delivery, and postpartum bodily changes, we thought we knew almost everything about the weird and wonderful functions and capabilities of the female human body. New research published in Developmental Cell, however, is shedding light on an interesting natural phenomenon that occurs when women are finished breastfeeding: the epithelial cells lining the breast ducts actually devour leftover dead and dying cells from the nursing process. So basically the cells that help form the alveoli (which are responsible for making and holding milk after a baby is born) then aid in the destruction and clean-up of the alveoli when breastfeeding is done. It sounds kind of crazy, but this process actually plays an important part in reducing inflammation, restoring tissue, and may even be a piece of the puzzle in better understanding the development of breast cancer as well as how a particular protein may be a part of effective cancer treatment. Read on for more about this fascinating discovery.
To better understand the molecular transformation that occurs, scientists identified the protein Rac1 as being a potentially important element. They already knew that Rac1 was integral for regulation of milk production as well as in the “eating” of immune cells (a process known as phagocytosis). Although immune cells later become active in the phagocytosis process, the breast’s own epithelial cells appear to do the early work, cleaning out milk fat and milk protein and preventing high levels of inflammation from occurring during this rather destructive phase.
This study, which involved deleting the Rac1 gene in female mice, showed that without the protein Rac1, swelling and inflammation occurred since the body couldn’t get rid of the dead and dying cells. The first litter of mice survived but was smaller, and subsequent litters died. In later pregnancies, mice then had a more difficult time regenerating tissue and producing milk.
Since Rac1 could suppress inflammation, scientists will explore how this protein plays a part in cancer development and treatment: the epithelial cells that play such a huge role in the clean-up process are the “same types of cells that over 90 percent of cancers come from.” Rac1 is over-expressed in various cancers (including breast cancer), leading scientists to recently consider Rac1 inhibitors as potential cancer treatment. This study, however, shows that blocking Rac1 could actually allow more inflammation to occur. Women are at an increased risk of developing breast cancer for five to ten years after pregnancy, which means further studies of Rac1 and its cellular interactions may help researchers understand the development of cancer. While the science and research world continues to figure out Rac1’s roles, we are going to add another item to the list of awesome things cells in our breasts can do: self-destruct and cannibalize on internal command.