more human-animal chimeras: mice with human breasts and milk

above is a mouse with mammary glands containing human breast tissue.
scientists at the whitehead institute for biomedical research have revolutionized the way we study human breast cancer. a team led by robert weinberg has developed a way to graft human breast tissue into the mammary glands of mice, producing mice that not only have human breast tissue growing inside them, but also produce human milk. these meeces' stromal cells are then genetically engineered with a virus that overproduces two proteins implicated in breast cancer, causing the mice to develop the same breast tumors that humans do. this creates a playground for scientists to study breast cancer and test new drugs without harming actual people.

full article at mit news