Mice grow human breast tissue

The breast tissue grew in the mice

US scientists have grown human breast tissue in mice which they hope will enable them better to study the development of cancer.

Researchers at the Whitehead Institute for Biomedical Research in Boston grafted human breast cells on to mice.

The animals went on to develop tissue closely resembling that seen in the normal human breast.

The research is published in the journal Proceedings of the National Academy of Sciences.

The promise the method brings to the study of normal and premalignant breast disease is enormous. Dr Daniel Medina

The key to the team's success was irradiating a portion of the fibroblast cells that were transferred with the human tissue.

The irradiation activated connective tissue cells that in turn created a hospitable, nutrient-rich microenvironment for the implanted human milk duct cells.

The team also found that outwardly normal breast tissue transferred into the mice occasionally developed into hyperplasias, which can be the precursors of cancer or cancerous themselves.

This finding supports the idea that ostensibly normal breast tissue can harbour small islands of genetically abnormal cells that can become cancerous.

It also suggests that cells in the breast's underlying connective tissue layers can release signals that spur cancer's progression.

The team says its techniques should prove useful for studying many of the steps that lead from normal human breast tissue to a variety of types of breast cancer.

In a commentary on the research published in the same journal, Dr Daniel Medina, and expert on molecular biology at Baylor College of Medicine, Texas, said science had relied greatly on rats and mice to study the changes that lead to cancer.

However, he said the technique had limitations because rodents and humans were not the same, and there were differences in the composition of the breast tissues.

He said: "The promise the method brings to the study of normal and premalignant breast disease is enormous.

"Researchers now have the means to develop transplantable cell lines of normal and premalignant human breast epithelium to test chemopreventive agents in an environment that resembles that from which human cancer arises."