Stem Cells May Be at Root of Cancer
New Research May Explain Why So Many Tumor-Fighting Treatments Now Fail
Stem Cells Drive Colon Cancer
In another experiment, Chu and colleagues sorted colon cancer cells
according to a molecular marker known as CD44 that appears on their
The marker was chosen because it fit the bill for a cancer stem cell, with
earlier studies showing it "possessed a capacity to reproduce itself,
regenerate, and produce tumors similar to the tumor of origin," he
Then, the researchers injected cells producing various amounts of CD44 into
mice. Results showed that the mice developed tumors after being injected with
as few as 10 cells producing high amounts of CD44. That's not many, when you
consider there are billions of cells in the body, Chu says.
Cancer cells that did not have CD44 on their surface were far less driven.
Researchers had to inject 5,000 or more of these cells into the mouse to induce
tumor growth, he says.
Wicha notes that CD44 is present on the surface of lung, breast, and many
other types of cancers as well. What this suggests, he says, is that novel drug
treatments blocking CD44 would curb the growth of many tumor types, not just
that of the colon.
Radiation Enhances Cancer Stem Cell Growth
In a third study reported at the meeting, researchers from the Ontario
Cancer Institute found that cancer stem cells may help explain why women with
breast cancer who are successfully treated with radiation are at increased risk
of developing leukemia down the road. Radiation therapy in mice enhanced blood
stem cell growth which could lead to increased risk for leukemia.
Wicha cautions that while all the research is exciting, there's still a long
way to go. "This is obviously a very important and exciting area of
research with great potential," says Len Lichtenfeld, MD, deputy chief
medical officer of the American Cancer Society in Atlanta.
"A lot of people believe, and rightly so, that it may help provide the
answers we have been looking for," he tells WebMD.
At the same time, "we do have to be cautious," says Lichtenfeld,
noting that researchers have had other promising theories about how cancer
develops that did not prove to hold true after rigorous examination.