A recent study, published in the journal Cell, suggests that aspirin could be effective in boosting the immune system in patients suffering from breast, skin and bowel cancer.
While researchers warn that the use of aspirin in the fight against cancer is still some way off, experiments on mice have proven encouraging.
Immunotherapy is growing in strength as a weapon against the disease, as research increasingly focuses on ways in which cancer apparently "tricks" the immune system into allowing it to develop.
One way in which cancer avoids the immune system is through "befriending" T cells, which seek out unwanted elements such as bacteria and viruses in the body's fight against disease, but mysteriously, do not attack cancer cells.
In the 1990s, a molecule that Japanese scientists called "Programmed Death 1" (PD-1) was found on the surface of T cells. US researchers then found that cancer tumors often produced a matching molecule, "Programmed Death Ligand 1" (PDL-1). In this way, the cancer is able to "trick" the T cells into joining, instead of fighting it, thus circumventing the immune system.
This discovery led to the development of a group of drugs known as "immune checkpoint blockade therapies."
Another way in which cancers appear to subvert the immune system involves prostaglandin 2 (PGE2). PGE2 normally causes inflammatory response and fever in bacterial and viral infections, but it has been known for some time to promote tumor growth in the gastrointestinal tract.
One theory is that the inflammatory process does not always end when it should. Chronic inflammation can eventually cause changes, such as the formation of new blood vessels and DNA mutations, which can give rise to tumors. Cells involved in certain types of inflammation have been found to produce secretions that promote tumors.
Reawakening the immune system
According to the team from the UK's Francis Crick Institute, who carried out this project, PGE2 molecules "dampen down" the response of the immune system, which enables the cancer cells to "hide." If PGE2 molecules can be destroyed, they say, the immune system will "reawaken," find and kill the cancer cells.
PGE2 in the body is produced by Cyclooxygenase, known as COX-1 and COX-2 enzymes. COX inhibitors are currently in the spotlight as a way to prevent the production of PGE2 in cancer patients. One way of inhibiting COX is through nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin.
This study found that certain types of cancer in mice were substantially slowed by combining aspirin or other COX inhibitors with immunotherapy.