We finally know why this common painkiller stops cancer from spreading

It’s a medicine cabinet staple. You’ve probably taken it for headaches, fever, or aches. But did you know that for over 50 years, scientists suspected it could help stop cancer from spreading? Now, we finally know how it works.

The painkiller in question? Aspirin. And thanks to a breakthrough by a team of British researchers, we now understand the mechanism that allows it to help the immune system destroy metastatic cancer cells. That’s a big deal, since metastases are responsible for 90% of cancer-related deaths. This discovery brings new hope that aspirin could one day become part of routine cancer care.

Not just anti-inflammatory after all

For decades, experts thought aspirin’s cancer-fighting abilities came from its anti-inflammatory properties. But the exact biological process remained a mystery—which meant doctors couldn’t confidently use it as part of standard treatment.

In this new study, scientists gave small doses of aspirin to mice with different types of cancer, including breast, colon, and skin. The results? Compared to untreated mice, those given aspirin developed far fewer metastases. Their blood also had lower levels of thromboxane A2, a compound the team believes plays a key role in the process.

A clear path for immune defense

So how does it work? Researchers discovered that thromboxane A2 helps cancer cells hide from the body’s natural defenses, especially T lymphocytes—immune cells that target threats like tumors. But when aspirin lowers thromboxane levels, that protective shield disappears. Suddenly, T cells can find and destroy those rogue cancer cells before they spread.

The team’s next goal is to run the same experiment with human participants. If aspirin triggers the same effect in people, it could reshape how we approach cancer care—and help pinpoint which cancers might respond best to this low-cost treatment.

Véronique Molénat

Journalist

Decoding how the body works—from organs, tissues and cells all the way down to organelles, molecules and atoms. Understanding how these elements fit together to create living systems. Figuring out why those systems sometimes go off-track. And then explaining it all in clear, accessible language. That has been my driving force for 30 years.

Trained in cell biology, animal physiology, nutrition, public health, and finally in science communication, I have explored health from many angles. Today, I put that expertise in the service of anyone who wants to make science understandable to all.