by James J. Galligan, Ph.D., Associate Chair,baby aspirin image
Department of Pharmacology and Toxicology

We are always looking for better drugs to treat diseases. Pharmaceutical companies invest billions of dollars in research and development to understand disease mechanisms so that new targets for drug treatments can be identified. Cancer of all kinds is a disease that everyone fears and fortunately there has been great progress in diagnosing and treating cancer. With a few exceptions, cancer is not the death sentence it was at one time.

Perhaps even better than treating an existing cancer, is preventing cancer in the first place. This is where a recent study by Rothwell and colleagues comes in. Their study published in the Lancet shows that daily, low doses of aspirin reduce the risk of developing colon cancer.

It has been known for many years that a baby aspirin taken daily (about 80 mg of aspirin) reduces the risk of heart attack and stroke. This is because aspirin reduces blood clots which can block the small blood vessels that supply the heart and brain.

Aspirin inhibits an enzyme called cyclooxygenase 1 (COX-1) in blood platelets. COX-1 synthesizes factors that cause platelets to clump (aggregate) and clumping platelets form blood clots. Aspirin also inhibits a related enzyme called COX-2. COX-2 accumulates at sites of tissue injury and inflammation. COX-2 is also found in pre-cancerous tissues in the colon called adenomas. COX-2 activity helps to transform adenomas into cancer cells. By inhibiting COX-2 lowly aspirin can help prevent colon cancer.

Rothwell and colleagues analyzed data from five different placebo-controlled studies of the effects of aspirin on the incidence of heart and stroke. They looked at the occurrence of colon cancer in the study participants and found that aspirin produced a substantial decrease in colon cancer rates.

There are a couple of important additional findings. Firstly, there was a modest dose-related effect. Aspirin doses of 30 mg per day or less had no effect on colon cancer rates while doses higher than 80 mg per day were no better than a dose of 80 mg. The reason this is important is because a major side effect of aspirin therapy is gastrointestinal bleeding. The risk of gastrointestinal bleeding increases with daily aspirin doses more than 80 mg per day. The risk of gastrointestinal bleeding with a daily aspirin dose of 80 mg is small but not zero. Anyone considering daily low doses of aspirin for reducing the risk of heart attack, stroke or colon cancer needs to consult with their doctor first.

Aspirin has been around for more than 100 years. It is inexpensive and if used properly it can help prevent some of the biggest killer diseases. Sometimes the answer is right there in front of us and in the case of colon cancer, aspirin has been sitting there quite awhile.

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by James J. Galligan, Ph.D., Associate Chair,
Department of Pharmacology and Toxicology

Aspirin is amongst the most commonly used drugs in the world.  It is well know for its pain and fever relieving effects and it is now widely used as a preventative treatment for heart attacks and strokes.  Aspirin is a derivative of salicylic acid which is found in the bark of willow trees.  Salicylic acid is very irritating so chemists at the German pharmaceutical giant Bayer modified the chemistry of salicylic acid to produce aspirin which is far less irritating.  Aspirin produces its beneficial effects by inhibiting two enzymes: cyclo-oxygenase 1 and cyclo-oxygenase 2 (COX-1 and COX-2).   COX-1 is present in the stomach lining and it is responsible for protecting the stomach lining against stomach acid.  This is why aspirin can cause an upset stomach or in more extreme cases, ulcers and bleeding.  COX-2 is responsible for producing inflammation and pain (more on COX-2 in a minute).  COX-2 is the target for drugs such as Celebrex which is claimed to produce the pain relieving effects of aspirin without the risk for an upset stomach or bleeding.

Despite the potential side effects (which in some people can be serious) of aspirin use, a new study published in the Journal of the American Medical Association indicates that aspirin may reduce the risk of death from colorectal cancer in patients previously diagnosed and treated for this disease.  Colorectal cancer is the second leading cause of cancer-related deaths in the United States so this finding has great life-saving potential.  An interesting finding in this study is that aspirin therapy was only beneficial in those patients who had tumors that expressed COX-2; no benefit was found in patients whose tumors did not express COX-2.  This is another example of the potential of “personalized medicine” where drug or other treatments for a disease can be tailored to the specific disease profile in a patient.  Personalized medicine could lead to higher success rates and also lower costs as ineffective treatments would not be used for patients that do not have a medical profile appropriate for that treatment.

While any drug treatments (including over-the-counter drugs) should be started only after consulting with your doctor, it seems that the simple aspirin tablet that can be found in everyone’s medicine cabinet is good for many things that might ail you.

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