U-M scientists find "stem cells" in human breast cancer




Updated 3:00 PM March 03, 2003
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U-M scientists find "stem cells" in human breast cancer

By Sally Pobojewski
Medical School Communications

Of all the neoplastic cells in human breast cancers, only a small minority—perhaps as few as one in 100—appear to be capable of forming new malignant tumors, according to published research by scientists in the U-M Comprehensive Cancer Center (UMCCC). The discovery could help researchers zero in on the most dangerous cancer cells to develop new, more effective treatments.

Dr. Michael Clarke, a professor of internal medicine, directed the study. "These tumor-inducing cells have many of the properties of stem cells," he says. "They make copies of themselves—a process called self-renewal—and produce all the other kinds of cells in the original tumor."

Although similar cells have been identified in human leukemia, these are the first to be found in solid tumors, Clarke says. The cells were isolated from primary or metastatic breast cancers removed from nine women treated for cancer at the Cancer Center.

The discovery—reported last week in the online early edition of the Proceedings of the National Academy of Sciences (PNAS)—also may explain why current treatments for metastatic breast cancer often fail, says Dr. Max Wicha, an oncologist and director of the Comprehensive Cancer Center.

"The goal of all our existing therapies has been to kill as many cells within the tumor as possible," Wicha says. "This study suggests that the current model may not be getting us anywhere, because we have been targeting the wrong cells with the wrong treatments. Instead, we need to develop drugs targeted at the tumor's stem cells. If we are to have any real cures in advanced breast cancer, it will be absolutely necessary to eliminate these cells.

"What this means for women with cancer is that, for the first time, we can define what we believe are the important cells—the cells which determine whether the cancer will come back or be cured," Wicha says. "Before this, we didn't even know there were such cells."

Given that tumor-inducing cells now have been identified in breast and blood cancers, Wicha and Clarke believe it is likely that similar cells drive the development of other types of cancer as well. The Comprehensive Cancer Center is establishing a new research program to identify stem cells in other cancers and develop new therapies to destroy them.

"What we are working on now is finding out what makes these tumor stem cells different from the other cells in a tumor," Wicha says. "Now that we can actually identify them, we can start developing treatments to specifically target and hopefully eliminate them."

"This is not a cure for cancer," Clarke says. "But it is a very promising lead, which will focus our efforts to try to find a cure for cancer."

In addition to Wicha and Clarke, the collaborators in the research study are Muhammad Al-Hajj, a U-M post-doctoral fellow and first author of the PNAS paper, and Sean J. Morrison, a Howard Hughes Medical Institute assistant investigator and U-M assistant professor of internal medicine, is a collaborator in the research study.

The original U-M study was funded by the National Cancer Institute. U-M has applied for a patent on the identity and function of tumor stem cells.

U-M scientists find "stem cells" in human breast cancer

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