Researchers have managed to grow human breast tissue on mice as part of an investigation into how breast cancer develops in humans.

Genetically-modified mice are often used in cancer research, but breast cancer works differently in mice than in humans. The hope is that by studying the transplanted tissue, researchers will get an insight into the early stages of the disease.

Previous attempts to grow human breasts on mice have only used epithelial cells. According to Nature these cells line the milk ducts, and are where breast cancers start. In this experiment, two types of cell are transplanted: the epithelial cells and fibroblasts, or support cells.

The fibroblasts are blasted with X-Rays before being transplanted. The research team. led by Weinberg of the Whitehead Institute for Biomedical Research in Boston, used cells from women who had had breast reduction surgery. Weinberg thinks the irradiated fibroblasts help the epithelial cells to survive, but isn’t quite sure how.

If the fibroblasts were made to produce a protein present in tumours, the epithelial cells became cancerous. This, the researchers say, suggests that latent mutations emerge, or are switched on by the protein. ®