MONDAY, Feb. 24, 2003 (HealthDayNews) -- Breast cancer may contain a tiny minority of aggressive "stem" cells that can give rise to entire new tumors, new research says.
As few as 100 of these cells can let the tumor make copies of itself, becoming a factory that makes all the other types of cells in the original tumor, says the study, appearing in this week's issue of the Proceedings of the National Academy of Sciences. Their ability to regenerate is much like that of stem cells, researchers say.
Even tens of thousands of other types of cells in the same tumor didn't create more cancer, the study says.
"We're really excited; we're extraordinarily excited," says study author Dr. Michael F. Clarke, a professor of internal medicine at the University of Michigan Medical School. By isolating these cells, they've narrowed the field that therapies may one day target in the overall confusing mix of cells in these tumors, he adds.
Detecting these cells could also lead to a way that will let doctors diagnose the disease sooner, says Clarke. However, even though human cancer tissue was used, the tests were done on mice, so a practical application for their findings is still in the future, although Clarke says their research might be useful for humans within five years.
"We're three steps away [from developing a drug]," Clarke says. Next, researchers will find out what pathways let these cells form tumors, then they will find out where the pathways are and focus on them. The third step is to develop drugs to attack these pathways.
More than 40,000 women die of breast cancer each year in the United States and it is the most common type of cancer in women.
Other scientists also see potential in this discovery.
This is "a very intriguing study, which provides molecular identification of particularly aggressive breast cancer cells and which suggests potential new avenues for diagnosis and therapy," says Dr. Calvin Kuo, an assistant professor of medicine at Stanford University.
The Michigan research builds on a previous study that saw a similar effect in a type of leukemia (blood cancer), but this is the first time these "stem" cells have been found in a solid cancer, the researchers say.
Figuring out how to tell the difference between the two kinds of cells took years for Muhammad Al-Hajj, a postdoctoral fellow and a co-author of the study. He and the team took tumor tissue from nine breast cancer patients, and discovered that eight of them had the same protein "fingerprint" on the surface of their cancer cells. The ninth had a biological variation that made the separation of cell types difficult, says Clarke.
In the remaining eight samples, the nasty "stem" cells had a pattern of surface proteins where there was a lot of a type called CD44 and little to none of a type called CD24. The researchers harvested cells showing this pattern and injected them into mice. As few as 100 of these cells caused tumors identical to the original to form, the researchers found.
Since an aggressive subset of cells has been found in both blood and breast cancers, the scientists think other types of cancer might be driven by them, as well.
More information
Learn about the disease by visiting the American Cancer Society or this extensive area from the National Institutes of Health's National Cancer Institute.
