Aug. 5, 2004 -- One of the great missing links in cancer resear
Aug. 5, 2004 -- One of the great missing links in cancer research isn't missing any more.
Some cancers appear to be linked to long-lasting infections. But nobody knew why -- until now. The new findings come from the lab of Michael Karin, PhD, at the University of California in San Diego. The Karin team's report is the cover story in the Aug. 6 issue of Cell.
Infections provoke an immune response from the body. Part of this response is inflammation. Inflamed tissues swell, redden, and leak fluids full of chemical signals to the immune system. Galen, the great Greek doctor, noticed a link between inflammation and cancer some 2,000 years ago. Our word "tumor," in fact, comes from the Latin word tumere, to swell.
"These findings really explain how inflammation can promote cancer. There is no question about it," Karin tells WebMD. "And if we learn how to decrease the effect of inflammation on cancer, we could prevent 20% or more of all cancers."
Herman Kattlove, MD, MPH, medical editor at the American Cancer Society, is more restrained about the findings.
"My sense is that most cancers are not related to inflammation," Kattlove tells WebMD. "Most cancers -- unless there is something we don't know -- most are not related to inflammation."
But Karin stresses the observation that more than one in five cancers worldwide is linked to long-term infections. Hepatitis viruses, he says, don't carry any cancer-causing genes. Yet they are linked to inflammation of the liver, which increases a person's chances of liver cancer.
Eric Jacobs, PhD, senior epidemiologist for the American Cancer Society in Atlanta, agrees that several kinds of cancer are linked to infections. And there's another line of evidence, he says.
"Aspirin use, and use of aspirin-like drugs that reduce inflammation, can reduce the risk of certain cancers," Jacobs tells WebMD. "The one strongly established link to lower risk in aspirin users is colorectal cancer -- and there's pretty good evidence in gastric cancers."
