Can a common, low-cost drug stop cancer from spreading? Researchers say aspirin, known for its pain-relieving and blood-thinning properties, may also help reduce the spread of certain cancers, and they have now uncovered the mechanism behind its effect.

Metastasis, or the spread of cancer cells from their original tumor to distant organs, is responsible for around 90 percent of cancer deaths worldwide. Earlier studies have shown that taking low-dose aspirin daily could reduce the spread of breast, bowel, and prostate cancers. However, the exact mechanism by which the drug could prevent metastasis was not known.

In the latest study published in the journal Nature, researchers discovered that aspirin works against cancer spread by stimulating the immune system, a finding they made by chance while investigating the process of metastasis.

Researchers know that when cancer cells detach from a tumor and spread to other parts of the body, the immune system, especially T cells, can recognize and attack them more effectively than while the cells remain within the tumor.

In earlier research, they identified a specific gene in mice, ARHGEF1, that plays a key role in cancer metastasis. This gene produces a protein that weakens T cells, making it easier for cancer to spread.

To explore potential treatments, they investigated how ARHGEF1 is activated and discovered that it is triggered by thromboxane A2 (TXA2), a molecule involved in blood clotting. This led the researchers to recognize aspirin's potential role, as it is already known to reduce TXA2 production, the reason why the drug is used to prevent blood clots, heart attacks, and strokes.

"It was a Eureka moment when we found TXA2 was the molecular signal that activates this suppressive effect on T cells. Before this, we had not been aware of the implications of our findings in understanding the anti-metastatic activity of aspirin. It was an entirely unexpected finding which sent us down quite a different path of inquiry than we had anticipated," Dr. Jie Yang, a researcher said.

"Aspirin, or other drugs that could target this pathway, have the potential to be less expensive than antibody-based therapies, and therefore more accessible globally," Dr. Yang added.

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