Bacteroides fragilis in the gut improves immunity and immunotherapy treatment responses.
Researchers from the Francis Crick Institute, the National Cancer Institute of the US National Institutes of Health and Aalborg University in Denmark have revealed that vitamin D encourages the growth of a type of gut bacteria in mice, which provides better cancer immunity.
The study published in Science found that vitamin D increases the amount of Bacteroides fragilis, providing better immunity to cancer in mice with transplanted tumours.
Cancer, including female breast, lung, bowel and prostate cancers, was responsible for more than 18 million new cases worldwide in 2020, according to Cancer Research UK.
After giving mice a diet rich in vitamin D, researchers discovered they had better immune resistance to experimentally transplanted cancers and improved responses to immunotherapy treatment.
Furthermore, this effect was seen when gene editing was used to remove a protein that binds to vitamin D in the blood and keep it away from tissues.
Researchers found that vitamin D acts on epithelial cells in the intestine and increases the amount of a bacteria known as Bacteroides fragilis, which offered mice better immunity to cancer as the transplanted tumours didn’t grow as much.
After giving mice Bacteroides fragilis, researchers observed better resistance to tumour growth compared to mice on a vitamin D-deficient diet.
Previous, inconclusive research has already suggested a link between vitamin D deficiency and cancer risk in humans.
Researchers explored this link by analysing a dataset from 1.5 million people in Denmark, which highlighted a link between lower vitamin D levels and a higher risk of cancer.
In addition, a separate analysis suggested that cancer patients with higher vitamin D levels were more likely to respond well to immune-based cancer treatments.
Caetano Sousa, head of the immunobiology laboratory, the Crick, said: “This could one day be important for cancer treatment in humans.
“More work is needed before we can conclusively say that correcting a vitamin D deficiency has benefits for cancer prevention or treatment.”
