Most cancer patients do not die from the primary tumor but from its metastases, which are secondary tumors formed by cells that have separated from the primary tumor.

Often, the primary tumor suffers from a lack of oxygen that causes stress and starts the process of spreading metastases. According to one theory, the primary tumor, using a continuous molecular signal, prepares a favorable environment in healthy tissue, before the first cancer cell is transported by the bloodstream to the new site. The primary tumor releases exosomes which are vesicles covered by a lipid membrane that act as messengers and prompt cells to create fertile ground for metastasis.

Scientists discover how aspirin could prevent some cancers from spreading

Metastasis is the spread of cancer cells from primary tumours to distant organs and is the cause of 90% of cancer deaths globally.

Metastasizing cancer cells are uniquely vulnerable to immune attack, as they are initially deprived of the immunosuppressive microenvironment found within established tumours.

It was known that people with cancer who take aspirin daily show fewer metastases than those who do not take this drug. Why this happened had remained a mystery. Now the mechanism has been observed in action in mice and reconstructed in research published in the journal “Nature” by the British University of Cambridge.

The researchers coordinated by Rahul Roychoudhuri have discovered that TXA2 is also the key to reducing metastases: this compound, in fact, causes the activation of a protein called Arhgef1, which interferes with immune cells capable of recognizing and eliminating cancer cells that have detached from the main tumor.

Inhibitors of cyclooxygenase 1 (COX-1), including aspirin, enhance immunity to cancer metastasis by releasing T cells from suppression by platelet-derived thromboxane A2 (TXA2).

These findings reveal a novel immunosuppressive pathway that limits T cell immunity to cancer metastasis, providing mechanistic insights into the anti-metastatic activity of aspirin and paving the way for more effective anti-metastatic immunotherapies.

With TXA2 suppressed by aspirin, immune cells are freer to hunt down escaped cancer cells. “When cancer first spreads, there is a unique window of opportunity in which cancer cells are particularly vulnerable to attack by the immune system,” says Roychoudhuri. “The therapies that manage to target this window – he concludes – could have a huge scope in preventing recurrence in patients at risk.”

https://www.nature.com/articles/s41586-025-08626-7