The daily dose of aspirin against cancer
Aspirin is one of the wonder drugs of the twentieth century. Since its discovery, it has been used to reduce fever, reduce inflammation and, more recently, protect against stroke and heart attacks. This 'cure-all' now seems to be emerging as a way to treat cancer. For colorectal cancer, treatment with aspirin halves the death rate. The reason for this appears to be that aspirin inhibits the production of the enzyme cyclooxygenase. Scientists Raymond DuBois and his colleagues at Vanderbilt University Medical Center, Nashville, Tennessee, describe their latest research in Cell, May 29, 1998. They treated people with colorectal (colon) cancer with nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin. This almost halved the death rate. The researchers see the connection in the fact that aspirin inhibits the production of the enzyme cyclooxygenase. In 80 percent of colon cancer cases, they found elevated levels of cyclooxygenase in tumor tissue compared to he althy tissue. From this, DuBois and his collaborators concluded that cyclooxygenase must be involved in tumor formation.
To study this, they grew tumor cells in the lab along with endothelial cells lining the colon and monitored the effects the cells had on each other. They found that cyclooxygenase stimulated the production of angiogenic factors in both endothelial and tumor cells. These factors cause angiogenesis - the joining of endothelial cells to form new blood vessels. The vascular networks supply tumors with vital nutrients and oxygen. Without this nutrition, they will not grow larger than two to three millimeters.
Cyclooxygenase comes in two closely related forms: COX-1 and COX-2. These appear to have slightly different effects on the development of tumors. While COX-2 is primarily produced by tumor cells, COX-1 originates from the endothelial cells themselves. More importantly, the angiogenic factors of the tumor cells, whose production is stimulated by COX-2, can also act directly on COX-1, and so the Boost production of angiogenic factors in endothelial cells. So how does aspirin fit into this picture? Because it inhibits both COX-1 and COX-2, aspirin can avoid cyclooxygenase-mediated angiogenesis. This does not mean that the angiogenic factors are not generated. However, by inhibiting COX-1 and COX-2, aspirin should at least ensure that the concentrations of these factors in the tumor are much lower than without the drug.
And although aspirin causes side effects such as nausea and bleeding in the gastrointestinal tract, it remains one of the most effective and safest curative drugs - important arguments for any new therapy for cancer.
