The natural compound in aspirin, salicylic acid, has been around for thousands of years.
It is derived from the bark of the willow tree and was used by Greek physician Hippocrates (460 -370 BC) to treat various ailments.
Interest in aspirin as an anti-cancer drug arose after researchers noticed that when patients who had a stroke and heart attack were given the drug, they had a much higher survival rate if they developed cancer, said Dr John Chia, a senior consultant medical oncologist at the National Cancer Centre Singapore.
There are, to date, more than 100 observational studies involving hundreds of thousands of patients which show that those who were prescribed aspirin for a variety of non-cancer reasons have a much lower risk of cancer death, he said.
However, as aspirin is linked to rare but potentially severe side effects of bleeding, it cannot be given routinely without proper clinical trial evidence and medical guidance, said Dr Chia.
Hundreds of research papers and studies have shown that aspirin blocks a wide variety of pathways that control cancer cell survival, growth and spread.
This can be broken down into a few broad categories: •Aspirin blocks an enzyme responsible for cancer cell growth, invasion and migration.
•It blocks the vascular endothelial growth factor, the principal growth factor responsible for cancer blood vessel growth.
•It blocks a molecule in cancer cells that prevents immune cells from attacking cancerous ones.
•It blocks the ability of platelets to "coat" cancer cells in the blood. Cancer cells have to invade the blood stream, and are then carried to distant organs by the blood. In the blood, they are exposed to "sheering" stress from the rapid movement of blood. They are also exposed to immune cells, which can also destroy the "floating" cancer cells. In the bloodstream, cancer cells attract platelets and become coated with a layer of platelets. This protects them from immune cell destruction and sheer stress. Aspirin blocks these platelets, thus making the cancer cells in the bloodstream far more exposed to destruction.
•It is an anti-inflammatory agent. Inflammation is the body's response to injury on a cellular level. Inflammation pulls in white blood cells to the site of injury and this leads to repair.
Cancer cells subvert the inflammatory response. It uses the inflammatory factors to drive cancer cell mutation and growth. Aspirin can block that.
Ng Wan Ching