Zeaxanthin Nutrient from Vegetables Boosts T Cells and Cancer Immunotherapy Efficacy in New Study

Researchers at the University of Chicago reported Wednesday that zeaxanthin, a nutrient found in fruits and vegetables, enhances the function of CD8+ T cells and improves cancer immunotherapy outcomes in preclinical models. According to the study published in *Cell Reports Medicine*, zeaxanthin stabilizes T-cell receptor complexes, boosting T-cell activation and tumor-killing ability in mouse models of melanoma and colorectal cancer.

The study, led by researchers in Chen’s laboratory at the University of Chicago, identified zeaxanthin as a potent enhancer of CD8+ T cell cytotoxicity against cancer cells, according to the research published Oct. 1, 2025, in *Cell Reports Medicine*. This stabilization triggers robust intracellular signaling, leading to increased T-cell activation, cytokine production, and improved tumor cell killing in preclinical models, the researchers reported.

Using a comprehensive screen of blood-borne nutrients, the team isolated zeaxanthin, a carotenoid found naturally in orange peppers, spinach, and kale, as a key immunomodulatory compound that stabilizes T-cell receptor (TCR) complexes on CD8+ T cells.

In mouse models of B16F10 melanoma and MC38 colorectal carcinoma, oral supplementation with zeaxanthin significantly slowed tumor growth compared with controls, according to the study. The nutrient alone enhanced anti-tumor immunity by promoting CD8+ effector T cell function but did not exhibit direct cytotoxicity against tumor cells at the concentrations tested. These findings were supported by multi-omics analyses demonstrating that zeaxanthin directly promotes TCR stimulation at the CD8+ T cell membrane, a mechanism distinct from its isomer lutein, which did not produce comparable effects.

The study also explored the synergy between zeaxanthin and immune checkpoint inhibitors, a class of cancer immunotherapies that remove inhibitory signals on T cells. When combined with checkpoint blockade, zeaxanthin supplementation produced significantly greater anti-tumor responses than immunotherapy alone in mouse models, the researchers said. Human TCR gene-engineered CD8+ T cells treated with zeaxanthin in vitro showed enhanced cytotoxicity against melanoma, multiple myeloma, and glioblastoma tumor cells, according to data presented by the team. “Our data show that zeaxanthin improves both natural and engineered T-cell responses, which suggests high translational potential for patients undergoing immunotherapies,” said lead investigator Chen in a university news release.

Further experiments confirmed that the effect of zeaxanthin on tumor control was independent of CD4+ T cells, as depletion of CD4+ cells did not diminish the nutrient’s enhancement of CD8+ T cell function. The study emphasized that zeaxanthin’s immunomodulatory activity stems from reprogramming CD8+ T cells rather than exerting direct cytotoxic effects on cancer cells. This specificity was demonstrated through co-culture assays involving mouse Pmel-1 CD8+ T cells and B16F10 melanoma cells, where zeaxanthin enhanced T cell-mediated killing without affecting tumor cell viability directly.

The research was supported by National Institutes of Health grants and presented at the American Association for Cancer Research (AACR) Annual Meeting 2025 as Abstract 6325. According to the University of Chicago Biological Sciences news release, the findings highlight a novel nutrition-immune axis, positioning zeaxanthin as a dietary supplement with potential to augment cancer immunotherapy outcomes. The nutrient’s established safety profile and widespread availability as an over-the-counter eye health supplement further support its translational potential, researchers said.

Chen’s lab has built on years of work investigating how dietary nutrients influence immune function. This study advances that research by identifying a specific plant-based compound that modulates T-cell receptor dynamics to enhance anti-tumor immunity. Laboratory tests showed improved TCR signaling and cytokine production in human CD8+ T cells treated with zeaxanthin, extending the findings beyond mouse models to human immune cells.

While the study focused on melanoma and colorectal cancer models, the enhanced cytotoxicity observed against multiple myeloma and glioblastoma cells in vitro suggests broader applicability. Researchers noted that zeaxanthin’s ability to boost both natural and engineered T-cell responses could benefit a range of cancer immunotherapies. The team underscored the importance of further clinical testing to evaluate zeaxanthin’s efficacy and safety as an adjunct to existing treatments.

Zeaxanthin’s role in stabilizing TCR complexes represents a distinct mechanism from other immunomodulatory agents, providing a new avenue for enhancing T-cell based therapies. The study’s findings contribute to a growing body of evidence linking nutrition and immune regulation, with implications for improving cancer treatment outcomes through dietary interventions.