Taking antioxidant supplements such as vitamins C and E may cause lung cancers to grow bigger and spread by stimulating the formation of blood vessels within tumours, according to a study in mice. One researcher has stressed that people with the condition shouldn’t try to avoid these antioxidants in their diet, but getting more than they need via supplements could cause harm.
Martin Bergö at the Karolinska Institute in Sweden and his colleagues previously found that supplementing with the antioxidants vitamin E and n-acetylcysteine caused lung cancers to spread in mice.
To better understand how this might occur, Bergö and a new team of researchers studied mice with a murine-specific form of lung cancer and mice that had been implanted with human lung cancer cells. They supplemented the mice’s water with vitamin C, which the animals naturally produce, and vitamin E and n-acetylcysteine, which they get from their diet.
These supplements were administered at increasing doses, all of which caused the mice’s levels of these antioxidants to exceed what was necessary. “Today in society, you have a lot of people who eat healthily, they have some supplements, and then they may have a ginger shot and a smoothie,” says Bergö. “If you do all that, you could end up with the levels of doses that we’re talking about.”
The researchers found that the higher the antioxidant doses that were given to the mice, the greater the rate of blood vessel formation within their tumours. This was true for the mice with the murine lung cancer and those with the implanted human cancer cells. Increased blood vessel growth would probably lead to the tumour growing and spreading, says Bergö, however, the researchers didn’t study this.
Bergö has stressed that people with any form of cancer shouldn’t alter their diet off the back of this research. “If you took away all the antioxidants in food, you would get sick for a range of reasons, such as vitamin deficiencies, and this would influence the cancer,” he says. “We’re focusing on increased [supplemented] doses above the required levels.”
In another part of the experiment, the researchers studied both human and mice lung cancer tumour organoids, balls of cells grown in a lab. After exposing them to higher-than-necessary doses of the three antioxidants, they found that these neutralised so-called free oxygen radicals within the organoids.
In the previous research, Bergö and his team implicated a protein called BACH1 in increasing tumour growth following vitamin E and n-acetylcysteine supplements. The latest study suggests that BACH1 is activated when there is a drop in free oxygen radical levels, with this activation inducing blood vessel formation.
With further research, the findings could point to a new way of treating some cancers, says Bergö. Blood vessel growth inhibitors are widely used in cancer treatments, but can have severe side effects, such as blood clots, he says. They might be more effective in people who have high levels of BACH1 in their tumours, which can come about both from supplements and mutations, he says.
While the experiments all involved lung cancer tumours, the researchers also searched genomic databases for other forms of cancer that may have elevated BACH1 levels. They found that these were often particularly high in kidney and breast tumours. This suggests that these conditions could also be better targeted via blood vessel growth inhibitors in people with high BACH1 levels, which can be screened for, says Bergö.