Common vitamin byproduct may help cancer evade immune system, study finds

Vitamin A itself is an essential nutrient, but one of its byproducts can accidentally "turn off" parts of the immune response against cancer, according to new research published in Nature Immunology.

Blocking that byproduct's effects can restore immune activity and may improve cancer immunotherapy, the findings suggest.

As these cells developed, the scientists noticed they naturally turned on an enzyme that makes retinoic acid, a molecule that comes from vitamin A.

The researchers also found that when dendritic cells made a lot of the retinoic acid, they were less able to send strong danger signals to the immune system.

When they removed the retinoic acid, the dendritic cells became stronger and better at activating T cells, which are the immune system's cancer-killing cells.

A second study, published in iScience by collaborators from the same research group, looked at how to develop drugs to block this process.

This led to the creation of a promising inhibitor that shuts down retinoic acid production in a controlled way, the same tool used in the first study's experiments, the researchers noted.

As these findings are based on laboratory and animal models, they may not fully reflect how retinoic acid functions in humans.

Also, the studies examined a specific vitamin A-derived molecule (retinoic acid) acting in immune cells, not dietary vitamin A intake or overall vitamin A status.

Vitamin A remains an essential nutrient for normal immune function, growth and vision, according to the National Institutes of Health, and extensive human studies have found no evidence that vitamin A causes cancer.