The inflammatory enzyme cyclooxygenase-2 (Cox-2) has earned a reputation as an agent provocateur in rheumatoid arthritis. Researchers in Finland now report that Cox-2 also shows up frequently in a common form of stomach cancer.
The work adds this malignancy to a list of tumors with a Cox-2 affiliation. These include cancers of the colon, pancreas, breast, lung, liver, and prostate. Some researchers suggest that aspirin's inhibition of Cox-2 may explain why it seems to defend against colon cancer. Others have found evidence suggesting that aspirin or other Cox-2 suppressors can inhibit breast and prostate cancers, as well.
Researchers have shown that, on the biochemical level, Cox-2 chemically alters prostaglandin, a hormonelike compound that stimulates inflammation and cell proliferation.
To verify earlier studies that hinted at a Cox-2 role in stomach cancer, the Finnish scientists examined tumors from 43 patients with a type of stomach cancer that resembles colon cancer. Of these, 25 tumors showed evidence of the Cox-2 enzyme, says study coauthor Ari Ristimäki, a physician at Helsinki University Central Hospital. The findings appear in the July Clinical Cancer Research.
In addition, tests detected Cox-2 in precancerous lesions in the stomachs of nine other volunteers. The enzyme doesn't show up in healthy stomach tissue, but it does appear when the lining of the stomach is ulcerated. Ironically, this indicates that Cox-2 may participate in the healing process, Ristimäki theorizes. The presence of Cox-2 seems to inhibit apoptosis, or cell suicide, and induce the formation of new blood vessels.
"There is no reason to think that inhibition of Cox-2 would not work [against] esophagus or stomach cancer, if it works in the colon," Ristimäki says. Although experiments indicate that Cox-2 inhibition suppresses the development of benign growths, such as polyps, solid data showing that these drugs prevent cancer in people are still lacking, Ristimäki says.
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Dannenberg, A.J. 2000. Cox-2 inhibitors and prevention of colon cancer. Clinical Cancer Research 6(November):1078.
Lebeau, D. 1998. Chemoprevention controversies continue. Lancet 352(Nov. 21):1683.
Seppa, N. 1998. Colon cancer treatment shows promise. Science News 153(Feb. 14):101.
Taketo, M.M. 1998. Cyclooxygenase-2 inhibitors in tumorigenesis (Part I). Journal of the National Cancer Institute 90:1529.
______. 1998. Cyclooxygenase-2 inhibitors in tumorigenesis (Part II). Journal of the National Cancer Institute 90:1609.
Wu, C. 1998. Looking at an alternative to aspirin. Science News 153(May 23):327.