A common nutrient known for eye health may have a surprising new role: helping the immune system fight cancer. Researchers at the University of Chicago have discovered that zeaxanthin, a plant-derived compound found in vegetables like spinach, kale, and orange peppers, can enhance the cancer-fighting ability of T cells. The study, published in Cell Reports Medicine, suggests that this accessible supplement could complement existing cancer immunotherapies.

How Zeaxanthin Strengthens T Cells

T cells, particularly CD8+ T cells, are crucial for detecting and destroying tumor cells. They rely on a structure called the T-cell receptor (TCR) to recognize cancer cells. The researchers found that zeaxanthin stabilizes and strengthens the TCR complex, boosting immune signaling and enhancing the T cells' tumor-killing efficiency.

In laboratory tests, mouse models given zeaxanthin showed slower tumor growth. When combined with immune checkpoint inhibitors-a cutting-edge immunotherapy-zeaxanthin significantly improved anti-tumor effects compared to treatment alone. Further experiments with engineered human T cells also showed enhanced tumor-killing against melanoma, glioblastoma, and multiple myeloma cells.

Safe, Accessible, and Promising

Zeaxanthin is already widely used as an over-the-counter supplement for eye health. Its safety and tolerability are well established, making it a promising candidate for clinical trials as an adjunct to cancer therapy.

“This discovery opens a new field of nutritional immunology, showing that natural compounds can directly boost the immune system's ability to fight cancer,” said Jing Chen, PhD, senior author of the study and Distinguished Service Professor of Medicine at the University of Chicago.

The Path Ahead

While the results are promising, the research is still in early stages. Most evidence comes from laboratory and animal studies, and clinical trials are needed to confirm benefits in patients. Still, the findings highlight the potential of combining dietary nutrients with immunotherapy to make cancer treatment more effective and widely accessible.

Chen's team has previously found other dietary compounds, such as trans-vaccenic acid (TVA) from animal sources, can also enhance T-cell activity-suggesting that both plant- and animal-based nutrients could offer complementary immune benefits.

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