Study: Only a Small Number of Breast Cancer Cells Can Form New Tumors

Researchers have found that not all breast cancer calls act alike, and that a small minority of breast cancer cells are capable of forming new tumors and spreading cancer throughout the body.

The researchers from the Universit of Michigan, reporting in the journal The Proceedings of the National Academy of Sciences, said the tumor-forming cells express a protein called CD44 but have none or very little of a protein known as CD24.

In the study, the researchers experimented with mice that had been injected with human breast cancer cells, most of them taken from women with cancer that had spread beyond the breasts.

They found that when as few as 100 breast cancer cells with the specific protein pattern were injected into the mammary tissue of mice, the animals developed new tumors. But mice injected with tens of thousands of other breast cancer cells did not.

"If you look at all breast cancer cells, only a few of them are able to form a tumor," said Dr. Michael Clarke, a professor of medicine at the University of Michigan. "We've identified which cancer cells are capable of forming a tumor."

Other sources: Proceedings of the National Academy of Sciences