Breast cancer is the most common type of cancer occurring in women. The therapy of particularly aggressive types of breast cancer still is a challenge or sometimes not possible at all. Model systems to study the development of breast cancer are urgently required. The nature of the cells that form breast tissue in healthy women is not fully understood, but it is speculated that stem cells are present that can regenerate the mammary glands during the lifespan of a woman in order to guarantee milk production after multiple pregnancies.

Christina H. Scheel, Helmholtz Center for Health and Environmental Research, Munich, Germany, and colleagues have developed an experimental tool to study the function of breast cells by growing them in a Petri dish. This method allows growing cells isolated from the breast tissue of a patient in a collagen gel. When the cells divide in the gel, they build hollow tubules with grape-like structures at the ends, reminiscent of the lobular units formed during normal development of the mammary gland, the organ in female mammals that produces milk.

The researchers found that organoid structures developed in a floating collagen matrix while increasing rigidity of the gel led to increased spreading of the cells. The team suggests that this is a property of normal breast cells which may be exploited by breast cancer cells. Application of this new method may give insight into how healthy breast cells develop into cancer cells. The model may also be applicable to other organs, such as the lungs.

• Quantification of regenerative potential in primary human mammary epithelial cells,
  J. R. Linnemann, H. Miura, L. K. Meixner, M. Irmler, U. J. Kloos, B. Hirschi, H. S. Bartsch, S. Sass, J. Beckers, F. J. Theis, C. Gabka, K. Sotlar, C. H. Scheel,
  Development 2015.
  DOI: 10.1242/dev.123554