Researchers at the Francis Crick Institute, the National Cancer Institute (NCI), the US National Institutes of Health (NIH), and Aalborg University in Denmark have found that vitamin D promotes an improvement in the gut microbiota in mice by increasing the presence of a type of bacteria called Bacteroides fragilis that improves their immunity to fight cancer.
The results of the study have been published in the journal Science and show that mice that consumed a diet rich in vitamin D had greater immune resistance against experimentally transplanted cancers and a better response to immunotherapy treatment. This effect was also observed when gene editing was used to eliminate a protein that binds to vitamin D in the blood and prevents its reaching the tissues.
Surprisingly, the team discovered that vitamin D acts on the epithelial cells of the intestine, which increase the amount of B. fragilis and that this bacteria improved the immunity of the mice against cancer, since the transplanted tumors did not grow as much, although researchers are still not sure how this happens.
To test whether the bacteria alone could improve immunity against cancer, Bacteroides fragilis was administered to mice fed a normal diet. These animals also showed increased resistance to tumor growth, but not when given a vitamin D-deficient diet.
Identify what factors distinguish a good microbiome from a bad one
Previous studies have suggested a connection between vitamin D deficiency and cancer risk in humans, although the evidence has been inconclusive, according to Cancer Research UK. To examine this possible association, researchers analyzed a data set of 1.5 million people in Denmark, which showed a relationship between low vitamin D levels and an increased risk of cancer.
A separate analysis of a population of cancer patients also suggested that people with higher levels of vitamin D were more likely to respond well to immune-based cancer treatments. Although Bacteroides fragilis is also found in the human microbiome, more research is needed to understand whether vitamin D helps provide some immune resistance to cancer through the same mechanism.
“Identifying the factors that distinguish a ‘good’ microbiome from a ‘bad’ one is a major challenge. “We discovered that vitamin D helps gut bacteria elicit immunity against cancer, improving the response to immunotherapy in mice,” said Evangelos Giampazolias, former postdoctoral researcher at the Crick and now leader of the cancer immunosurveillance group at Cancer Research UK. Manchester Institute.
“We discovered that vitamin D helps intestinal bacteria provoke immunity against cancer, improving the response to immunotherapy in mice”
“A key question we are currently trying to answer is how exactly vitamin D supports a ‘good’ microbiome. If we can answer this question, we could discover new ways in which the microbiome influences the immune system, potentially offering interesting possibilities for preventing or treating cancer,” he adds.
“What we have shown here was a surprise: vitamin D can regulate the gut microbiome to favor a type of bacteria that gives mice better immunity against cancer.” “This could one day be important for cancer treatment in humans, but we don’t know how or why vitamin D has this effect through the microbiome. More work is needed before we can conclusively say that correcting a vitamin D deficiency has benefits for cancer prevention or treatment,” concludes Caetano Reis e Sousa, head of the Crick’s Immunobiology Laboratory and senior author.
