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- Article from the Karolinska Institutet
- Subject: Health & medicine
Supplements with vitamin C and other antioxidants can do more harm than good. Antioxidants stimulate cancer tumors to form new blood vessels, which accelerates their growth and spread. A study shows that.
Antioxidants counteract free oxygen radicals that can have harmful effects in the body. They are therefore commonly found in various food supplements. But too high doses can be harmful.
– You shouldn’t be afraid of antioxidants in the regular diet, but most people don’t need an extra supplement of antioxidants. It can even be harmful for cancer patients and people with an increased risk of cancer, says researcher Martin Bergö at Karolinska Institutet, KI.
In a new study, researchers have investigated how antioxidants affect cancer tumors.
– We have found that antioxidants activate a mechanism that causes cancer tumors to form new blood vessels, which is surprising because it was previously thought that antioxidants have a protective effect. The blood vessels supply nutrients that help the tumor grow and spread in the body, says Martin Bergö.
Activated protein behind new blood vessel formation
The research group has previously shown that antioxidants such as vitamin C and E accelerate the growth and spread of lung cancer by stabilizing a protein called BACH1. The protein is activated when the level of free oxygen radicals drops. This happens, for example, when extra antioxidants are supplied via the diet or when spontaneous mutations in the tumor cells activate the body’s own antioxidants.
The researchers have now been able to show that the activation of BACH1 leads to increased new formation of blood vessels, so-called angiogenesis.
May lead to better treatment
Attempts are underway to develop drugs that suppress the new formation of blood vessels, so-called angiogenesis inhibitors. But the results have not been as successful as hoped, according to KI researcher Ting Wang.
– Our study opens up more effective ways to prevent angiogenesis in tumors. For example, patients whose tumors have high levels of BACH1 could respond better to treatment with angiogenesis inhibitors than patients with low BACH1 levels, she says.
Two mechanisms cooperate in tumors
Previous research has shown that low oxygen levels, hypoxia, are required for cancer tumors to produce new blood vessels. The new mechanism the researchers have identified shows that tumors can form new blood vessels even at normal oxygen levels.
The study also shows that BACH1 is regulated in a similar way to the protein HIF-1a – a mechanism that was awarded the Nobel Prize in Medicine in 2019 and which means that cells can adapt to changes in oxygen levels. The new KI study shows that these two mechanisms work together in the tumors.
Microtumors were studied
The researchers have used several different cell biology methods and above all studied lung cancer tumors using organoids – small cultured microtumors from patients – but also mice and tumor samples from breast and kidney cancer from humans.
Tumors where BACH1 was activated, either through the addition of antioxidants or through overproduction of the protein, were found to produce more new blood vessels and to be extra sensitive to angiogenesis inhibitors.
– The next step is to investigate in detail how the levels of oxygen and free radicals can regulate the BACH1 protein, and we will continue to study the clinical significance of our results. We will also proceed with similar studies in other forms of cancer such as breast, kidney and skin cancer, says Ting Wang.
Scientific study
Antioxidants stimulate BACH1-dependent tumor angiogenesis, Journal of Clinical Investigation.
Contact:
Martin Bergö, professor at the Department of Life Sciences and Nutrition, Karolinska Institutet, [email protected]
