No, it's not time to start gobbling the little white pills. Aspirin, that mainstay of Mom's medicine cabinet, causes severe stomach bleeding in many unsuspecting users. Today, aspirin is recognized as a particularly powerful drug.
Perhaps more powerful than anyone thought, suggest Helen M. Arthur, PhD, and colleagues at the University of Newcastle in England.
In test-tube studies, the researchers find that aspirin does what some of the most cutting-edge new anticancer drugs do. It seems to keep newborn cancers from growing the blood vessels they need to become full-blown tumors -- a process called angiogenesis.
"Aspirin, if we can get it into the body safely, can inhibit angiogenesis," Arthur tells WebMD. "We need to find the molecules responsible for this effect, and then find even better drugs. But for the moment, aspirin is pretty hot."
Arthur and colleagues report their findings in The FASEB Journal.
Aspirin's Unexpected Effect
Many studies have found that people who regularly take aspirin -- though they do have more stomach ulcersulcers -- also get cancer less often. Why?
Like other drugs classified as NSAIDs (nonsteroidal anti-inflammatory drugs), aspirin blocks important enzymes called Cox-1 and Cox-2. It's been thought that this was behind aspirin's suspected anticancer effect.
Now Arthur's team has made the startling finding that aspirin's anticancer effect may not be due to blocking Cox enzymes at all.
The researchers cultured human blood vessel cells in a test tube. The cells grew in a three-dimensional matrix that allowed them to begin to form new blood vessels. When exposed to aspirin -- the same concentration seen in the blood after a person takes two regular-strength aspirin -- the cells looked perfectly healthy. But they did not form new blood vessels.
Like most scientists, Arthur and colleagues suspected this effect was due to blocking Cox enzymes. So they exposed the cells to Celebrex. Celebrex only blocks Cox-2, the form of Cox suspected of promoting cancer. But Celebrex didn't keep new blood vessels from forming. Neither did another, experimental Cox-2 inhibitor -- nor did the two in combination.
Aspirin is a form of a compound called salicylate. Salicylate comes from willow bark, an ancient remedy for fever and headache. Unlike aspirin -- and unlike Celebrex -- salicylate doesn't block Cox as efficiently. Arthur and colleagues put salicylate in the test tubes with the blood vessel cells. To their astonishment, it, too, blocked angiogenesis.
"We scientists still have to show that this is happening in real life, not just in the test tube," Arthur cautions. "We need to test it in animals."
Even so, Michael J. Thun, MD, vice president of epidemiology and surveillance research for the American Cancer Society, calls the findings "provocative."
"This study won't settle the scientific argument over whether there's more to aspirin than Cox inhibition," Thun tells WebMD. "But if it bears out that there is a Cox-independent mechanism behind aspirin's cancer-inhibiting effect -- if that can be proved definitely -- that would be a very important finding."
Aspirin Benefit, Aspirin Risk
Here's why you shouldn't start popping aspirin to ally your cancer fears.
Even if aspirin does turn out to have remarkable anticancer properties, it still has to get into the bloodstream to work. Unfortunately, aspirin is taken by mouth. From there it goes to the stomach -- and that's where the trouble starts.
In the stomach, aspirin immediately dissolves and reaches very high concentrations. At these concentrations -- far higher than those eventually achieved in the blood -- aspirin is very toxic to the cells lining the upper digestive system. If there's any tear or injury, aspirin prevents healing. This can lead to fatal bleeding.
"At this point, no health agency anywhere recommends that people start regularly taking aspirin to reduce their risk of any cancer," Thun says. "The risk of bleeding is still larger than the risk you would prevent."
Arthur and Thun warn that nobody should be taking regular aspirin unless they are under a doctor's regular care. It's only worth the risk for people at high risk of heart diseaseheart disease.
And that is another place where aspirin's angiogenesis-blocking power may play a role, Arthur says. Angiogenesis isn't just important to cancer. It also plays a role in heart disease by destabilizing plaque that builds up in the arteries.
"Not just cancer is involved here," Arthur says.