Vitamin A Byproduct Found to Weaken Anti‑Cancer Immune Response in Lab Study

Researchers at the Princeton University Branch of the Ludwig Institute for Cancer Research report that retinoic acid, a molecule the body makes from vitamin A, can dampen key immune cells’ ability to attack cancer in lab and animal models, suggesting a new way tumors may evade the immune system. In a Nature Immunology study, they found that dendritic cells naturally switch on an enzyme that produces retinoic acid, and when levels are high, those cells send weaker 'danger' signals and less effectively activate cancer‑killing T cells, reducing the impact of experimental dendritic‑cell vaccines. A companion iScience paper from the same group used computer modeling and drug‑screening to design small‑molecule inhibitors that block the enzymes making retinoic acid, which in turn restored stronger immune activation in preclinical tests. The authors stress that vitamin A itself remains an essential nutrient and that their work focuses on a specific downstream metabolite within immune cells, not on dietary intake, but say the findings could eventually be used to fine‑tune cancer immunotherapies by transiently blocking this pathway. Outside experts note that, while promising, the results are still limited to lab and animal models and will need confirmation in human studies before any changes to clinical practice.