Tumours in a particularly aggressive form of breast cancer may originate from cells lining the mammary duct — not from mammary stem cells as previously thought.
Jane Visvader and Geoffrey Lindeman at the Walter and Eliza Hall Institute of Medical Research in Victoria, Australia, and their colleagues compared the breast tissue of healthy women with and without mutations in the gene BRCA1, which significantly increase the risk of breast cancer.
Tissue with mutated BRCA1 harboured a larger population of luminal progenitor cells, and these were able to proliferate without the growth factor necessary for the division of other cell types, including mammary stem cells. Uncontrolled growth is a feature of cancer cells. The authors also found that normal luminal progenitors, precancerous tissue from BRCA1 carriers and basal breast tumours had similar gene-expression profiles.