Scientists at the University of Cambridge and Oregon Health & Science University say some cancers evade immune attack by releasing a natural antioxidant that deprives T cells of a molecule they need to switch on their killing function. The finding, published in Science, could help improve cancer immunotherapies that do not work for every patient.
Key facts
- Researchers found that tumours can release Peroxiredoxin 1, or PRDX1, a natural antioxidant.
- PRDX1 strips away reactive oxygen species that T cells need to activate and destroy cancer cells.
- In mouse models, removing the cancer cells’ ability to make PRDX1 increased immune-cell activity and limited tumour growth.
- Analysis of human cancer data and patient tumour fluid also pointed to the same PRDX1 mechanism.
- The team says the results may help explain why antioxidant supplements have not reduced cancer risk in trials and may have worsened outcomes in some cases.
What does this mean for patients and immunotherapy research?
The work suggests a new biological route that cancers may use to blunt T cell responses, which matters for research into immunotherapy resistance. It also raises the possibility that changing tumour redox chemistry, rather than broadly suppressing it with antioxidants, could be relevant to future treatment strategies.
How do cancer cells stop T cells from working?
They do it by releasing PRDX1 into their surroundings. According to the study, that antioxidant mops up reactive oxygen species, and T cells depend on those molecules to activate their cancer-killing machinery. When the signal is removed, the immune attack is weakened.
The researchers analysed fluid surrounding tumours in mice, edited cancer cells with CRISPR so they could no longer produce the antioxidant, and then compared those results with published human cancer datasets and tumour samples from patients. Across those approaches, PRDX1 kept appearing as the same escape mechanism.
Why does this matter for immunotherapy?
Immunotherapy can be highly effective, but it does not help all patients. The Cambridge-led team says that blocking the PRDX1 pathway made some tumours that had not responded to immunotherapy start responding, suggesting the mechanism may be a useful target for future treatment development.
Could antioxidant supplements affect cancer defence?
The study points to a possible explanation for why large randomised trials have not shown cancer-risk reduction from antioxidant supplements, and in some cases have reported worse outcomes. The researchers stress the findings are preclinical and say people living with cancer should not change treatment or diet without medical advice.
FAQ
What did the researchers find in human cancers?
They found evidence that human cancer cells also release PRDX1 into their surroundings, including in analyses of proteins from cancer cell lines, gene activity across thousands of tumours, and fluid taken from tumours removed from patients.
Where was the research published?
The study was published in Science on 3 September 2026.
