Human breasts grown on mice

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Human breasts grown on mice 3-25-04

http://wrightworld.net/science.htm

Lab mice have grown tissue more usually confined to a bra - lumps of human

breast. The growths should help researchers work out how cancer develops.

Researchers commonly use genetically engineered mice to study cancer, but

the animal disease differs slightly from the human one. So researchers have

sought to transplant human breast tissue into mice to make a better model.

Now Robert Weinberg of the Whitehead Institute for Biomedical Research in

Boston and his team have succeeded. They report their method in the

Proceedings of the National Academy of Sciences. The key, Weinberg says, is

to transplant two types of human breast cells into the mice, one of which

has been blasted with radiation. The cells grow into human-like breast

tissues, complete with milk ducts. Unlike human breasts, however, the mice's

growths sit flush to the chest. Humans are unusual in this respect, says

Daniel Medina who studies breast cancer at Baylor College of Medicine at

Houston, Texas: " In few other species are breasts pendulous. "

 

Hocus-pocus - In the past, some researchers transplanted only one type of

breast cell, called epithelial cells, into mice. These cells line the milk

ducts, and are where breast cancers start. But such attempts were " doomed to

failure " , says Weinberg, because they lacked a second element of human

breast tissue - support cells called fibroblasts. So Weinberg's team took

fibroblast tissue from women who had undergone breast reduction surgery.

They blasted half the fibroblasts with X-rays, injected both healthy and

irradiated cells into mouse mammary glands, and grafted human epithelial

breast cells alongside. Weinberg thinks that irradiating the fibroblasts

helps the epithelial cells survive. He is not sure how it works, but it may

provoke an inflammatory response that helps to protect the cells. " It's

hocus-pocus, " he says. The human-breasted mice also develop cancer in much

the same way as humans. Scientists think breast cancer starts when one

epithelial cell gets a mutation in its DNA and starts dividing wildly into a

tumour. When the team modified the human fibroblasts so that they made a

protein often over-produced in human breast tumours, the mice developed

cancer in their epithelia. This suggests that the transplanted epithelial

cells were harbouring mutations that turned cancerous in response to signals

from neighbouring cells. Researchers hope the new system will help them

tease out these signals and, perhaps, find ways to stall them. " It's a very

big advance, " says Medina.