Stem cell environment may give rise to cancer

The stem cell niche is a highly specialized microenvironment which surrounds adult stem cells. These niches are key regulators of stem cell activity in mammary tissue. New research suggests that defects of these niches appear to be capable of giving rise to breast cancer.

“This study helps us understand adult stem cells differently than we previously did. Particularly, when looking for the causes of breast cancer, we must take into account the stem cell as well as the environment that surrounds it,” said Dr Robert Dickson, co-director of the breast cancer program at the Lombardi Comprehensive Cancer Center.

The study used genetically engineered mice as models of ductal or lobular breast cancer that is caused by overproduction of certain proteins. These proteins (c-Myc and TGF-alpha) exist naturally in the body, but when produced in excess in mammary tissue cells, breast cancer can develop.

Studies show that there are five different types of cells in normal breast tissue. Two of the cell types are stem cell-like and give rise to the other three. The present investigation revealed not only that each cell population has a different size in normal breast tissue, but also that the different cells are arranged in particular relationships to each other. The arrangements form repeating units called stem cell niches and provide nest-like microenvironments that house the adult stem cells and their immediate daughter cells.

In the mice that expressed excess amounts of either of the cancer-producing proteins, the size of the cell populations were significantly changed relative to each other. The order of the cell arrangements was disrupted in the stem cell niches of mice with breast cancer. These results provided the first evidence that each cell population may play a different role in the development of breast cancer and that the environment in which a cell grows can influence its chance of becoming cancerous.