The results, published in Science Translational Medicine, are confirmed in studies on human lung cancer cells.
Antioxidants are present in food, pharmaceuticals, and nutritional supplements and are often claimed to fight cancer. However, the scientific evidence for this claim is heavily debated.
Researchers at the Sahlgrenska Academy, University of Gothenburg, now show that antioxidants can actually speed up the progression of cancer.
The study, published in Science Translational Medicine, was presented at a press conference in Washington DC on January 29th.
More and larger tumours
In the study, Professor Martin Bergo and his colleagues gave mice with lung cancer extra antioxidants in their diet. The results showed that the antioxidant-fed mice suffered larger and three times as many tumours.
They also died twice as fast as the mice in the control group.
Identified the mechanism
The team has been able to confirm the results with human lung cancer cells and has also identified the mechanism behind the effect.
‘When the antioxidants attack reactive oxygen radicals in the tumors, a protein called p53 is deactivated. p53 has a neutralising effect on tumors, and when it’s gone the tumours can grow faster and more aggressively,’ says Martin Bergo.
A serendipitous finding
The discovery was a serendipitous finding in another research project.
‘We didn’t expect to find a difference, or maybe that the antioxidant-fed mice would develop smaller tumours. Instead, their cancer became a lot more aggressive,’ says Professor Per Lindahl at the Sahlgrenska Academy, who was also involved in the study.
Equivalent of an ordinary multivitamin
The mice did not receive excessive doses of antioxidants, but rather the equivalent of what a person would receive from an ordinary multivitamin.
However, Lindahl says that the study does not provide any conclusive evidence that people should stop taking antioxidants, and emphasises that the study concerns how antioxidants affect the progression of cancer and not the risk of developing cancer.
‘For people who already have a small lung tumor but don’t know it, there is a risk that antioxidants may speed up the progression to cancer. Consequently, people in obvious risk groups, such as smokers, may consider not taking extra antioxidants, but we still have no scientific support for such a general recommendation,’ says Lindahl.
Can effect patients with chronic lung disease
However, the study may lead to a reconsideration of the treatment of patients with chronic obstructive pulmonary disease, COPD. In the study, the researchers studied two commonly used antioxidants, vitamin E and acetylcysteine. Since acetylcysteine dissolves mucus, it is often used by COPD patients.
‘Many COPD patients have been smokers and therefore have a higher risk of lung cancer. It is too early to give recommendations regarding the use of acetylcysteine in COPD patients, but our study clearly points to a need for new research on this topic,’ says Bergö.
Study on other cancer types
In a next step, the Gothenburg researchers will explore whether antioxidants have similar effects on other types of cancer and whether other types of antioxidants yield the same findings. They will also study whether antioxidants in healthy mice affect their risk of developing cancer in the future.
The article Antioxidants Accelerate Lung Cancer Progression in Mice was published in Science Translational Medicine on January 29th.
Science Translational Medicine: www.sciencemag.org
Antioxidants are chemical substances that neutralise so-called free radicals and can thereby protect cells from damage. Examples of antioxidants include vitamins, flavonoids and carotenes. Antioxidants are naturally present in for example fruits and berries and are also found in nutritional supplements and medicines. Cells in the body also produce their own antioxidants for protection against free radicals.
Martin Bergö, professor at the Sahlgrenska Cancer Center, University of Gothenburg
+46 (0)733 12 22 24
Per Lindahl, professor at the Wallenberg Laboratory, Sahlgrenska Academy, University of Gothenburg
+46 (0)709 52 28 58