Breast Tissue and Stem Cells

There are many types of stem cells but the key stem cells involved in breast tissue development and growth are called mammary stem cells. One important area of research is to better understand mammary stem cells so that we can learn more about how breast cancer develops. In turn, we can develop more effective treatments for breast cancer.

Mammary Stem Cells

These particular stem cells play a pivotal role in new breast tissue. Throughout a woman’s monthly menstrual cycle, they replenish her breast tissue. When a woman experiences pregnancy and breast-feeding, these stem cells continue to play a key role in the growth of new breast tissue.

Your Monthly Cycle

During your monthly cycle, your ovaries produce the hormones oestrogen and progesterone. It is known that chronic exposure to the hormones, however, increases a woman’s risk of breast cancer. The more menstrual cycles a woman has, the higher her risk of breast cancer.

While we know that breast cancer occurs when breast cells grow in an uncontrolled manner, we have not been clear on just how oestrogen and progesterone influence the cells to raise a woman’s risk of breast cancer. For this reason, researchers are focused on investigating how the two hormones affect normal, healthy breast cells.

Understanding Mammary Stem Cells

In conjunction with these two hormones, a mammary stem cell responds with growth and where the hormones are reduced or removed, its growth similarly decreases.

When tested on mice, reducing the hormones caused the numbers of the stem cells to go down. If hormone levels were brought back to normal afterward, however, the stem cells never managed to function as they did before the hormone deprivation.

It’s thought that this might shed light on why certain anti-hormone therapies used to prevent another occurrence of breast cancer seem to protect a woman against breast cancer even after the treatment ends. This shows that even though hormone levels have gone back to normal, there is some sort of long-term impact to the stem cells.

Mammary Stem Cells During Pregnancy

If a woman were to receive a stem cell transplant, this mammary stem cell can then create a mammary gland. During pregnancy, a woman has more mammary stem cells. There is a specific molecule secreted during this time that is activated by pregnancy hormones, which then ‘awakens’ the stem cells. There are some studies ongoing now that look at how inhibiting this molecule can treat breast cancer by limiting its ability to grow and spread.

Preventing and Treating Breast Cancer

Overall, these studies together show that if we can block these paths that control the activity of stem cells, we can better understand, prevent and treat breast cancer. It will likely mean that treatment has to go further than blocking just one pathway.

Instead, all paths will have to be taken into account to prevent mammary stem cells from increasing in number. It is certainly no easy task for those who study and develop such experiments but offers hope that we are closer to finding better ways to address breast cancer.