Aspirin could boost the effectiveness of cancer immunotherapy treatment

Giving cancer patients aspirin at the same time as immunotherapy could boost the effectiveness of the treatment, according to new research published in the journal Cell.

Researchers found that combining immunotherapy with aspirin substantially slowed bowel and melanoma skin cancer growth in mice, compared to immunotherapy alone.

Study author, Professor Caetano Reis e Sousa, and senior group leader at the Francis Crick Institute, said: “We've added to the growing evidence that some cancers produce prostaglandin E2 (PGE2) as a way of escaping the immune system. If you can take away cancer cells' ability to make PGE2 you effectively lift this protective barrier and unleash the full power of the immune system.

“Giving patients COX inhibitors like aspirin at the same time as immunotherapy could potentially make a huge difference to the benefit they get from treatment. It's still early work but this could help make cancer immunotherapy even more effective, delivering life-changing results for patients.”

Aspirin is part of a group of molecules called COX inhibitors and is a form of non-steroidal anti-inflammatory drug (NSAID). They are commonly prescribed for pain relief and to reduce inflamation. However, researchers have also found that aspirin and other COX inhibitors can stop the production of PGE2 and help ‘reawaken’ the immune system.

Francis Crick Institute researchers, funded by Cancer Research UK, have found that skin, breast and bowel cancer cells often produce large amounts of PGE2. This molecule dampens down the immune system's normal response to attack faulty cells, which helps cancer to hide.

The study has revealed that this molecule allows the tumour to thrive and may explain why some immunotherapy treatments have not been as effective as previously hoped.

Cancer Research UK's chief clinician, Professor Peter Johnson, continued: “PGE2 acts on many different cells in our body, and this study suggests that one of these actions is to tell our immune system to ignore cancer cells. Once you stop the cancer cells from producing it, the immune system switches back to 'kill mode' and attacks the tumour.

“This research was carried out in mice so there is still some way to go before we will see patients being given COX inhibitors as part of their treatment. But it's an exciting finding that could offer a simple way to dramatically improve the response to treatment in a range of cancers.”