Low doses of a drug prescribed for arthritis appear to prevent growth of
colon cancer in laboratory animals, and might mean that the drug could
be used to prevent the disease, researchers suggested.
Mice that were genetically altered to be susceptible to developing polyps
in the colon which can often result in cancer. The drug rofecoxcib reduced
all polyp formation by 55 percent and reduced by 80 percent formation of
the large polyps considered most likely to turn into cancers, said Jillian
Evans, director of pharmacology at Merck & Co., West Point, Pa.
"Based on the success of the animal studies, we have begun clinical trials
with rofecoxcib in patients who are susceptible to different forms of colon
cancer," Evans said at the annual meeting of the American Association for
the Advancement of Science in San Francisco. Rofecoxcib is a member of
the class of drugs known as COX-2 inhibitors. Another member of the class,
celecoxib has been licensed in the United States for treating patients
with a familiar form of colon cancer. Evans said her animal studies supports
the evidence that the COX-2 inhibitors could play a role in preventing
cancer.
Evans said the difference between the two drugs is that rofecoxcib -- at
least in the animal trials -- was able to markedly prevent development
of cancers at doses that are comparable to what a person would take. She
said celecoxib is taken at higher than normal doses as a cancer preventive.
Both celecoxib and rofecoxcib are also used to prevent inflammation and
pain associated with arthritis.
"There is a role for COX-2 in development of polyps," said Charles Serhan,
director of the Center for Experimental therapeutics, at Brigham and Women's
Hospital, Boston. He said the drugs might be useful in countering some
of the effects created by COX-2 molecular actions. Evans said that
COX-2 signals cells to create a bioactive lipid -- a fatty substance --
which can enhance tumor progression by causing cells to proliferate abnormally.
She said COX-2 also helps recruit blood vessels which grow to nourish tumors.
COX-2 overproduction is also believed to hinder the ability of the immune
system cells to eradicate cancerous cells. The use of the COX-2 inhibitors,
Evans suggested, might be effective in a wide variety of cancers. "About
80 percent of colon cancers express COX-2," she said. "There is some form
of COX-2 in almost every other cancer, although it varies in the amount."
Because the new animal studies she reported involve taking rofecoxcib at
normal dosages, Evan said the drug might be administrated as a daily cancer
preventive agent in much the way aspirin is taken by many individuals to
reduce the risk of heart disease.
Serhan, who also is studying how bioactive lipids work in the body, said
he is trying to determine how chemicals in the body react to inflammation
seen in heart disease and arthritis. He said that if these natural chemicals
in the body can be isolated, they could be used to make drugs that could
prevent diseases without causing unwanted side effects. Serhan is particularly
looking at properties of fish oils and aspirin and their molecular-level
mechanisms that produce anti-inflammatory effects.
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2001 by United Press International.
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