New populations of breast stem cells that guarantee the creation, expansion and maintenance of the diverse cell lineages of the mammary gland during pregnancy and throughout life have been identified by European scientists. According to the researchers, this discovery opens new avenues to uncover the cells at the origin of the different subtypes of breast cancers.

A European team of scientists has identified new populations of breast stem cells that guarantee the creation, expansion and maintenance of the diverse cell lineages of the mammary gland during pregnancy and throughout life. The study was funded in part by CANCERSTEM ("Stem cells in epithelial cancer initiation and growth"), a project that received a European Research Council Starting Grant worth EUR 1.6 million under the EU's Seventh Framework Programme (FP7).

The two distinct stem cell types identified, together form cell lineages that maintain the mammary gland: luminal stem cells that differentiate into either ductal or milk-producing cells, secreting water and nutrients required to ensure the survival of young mammalian offspring; and stem cells giving rise to myoepithelial cells that through their contraction guide the circulation of the milk throughout the ductal tree toward the nipple.

According to the scientists, these findings radically change our understanding of the regenerative potential of the mammary gland during physiological conditions. In addition, they will be extremely important for those studying development, stem cells and mammary glands but also opens new avenues to uncover the cells at the origin of the different subtypes of breast cancers, a very important and unanswered question.