Targeting mucosal-associated invariant T cells using riboflavin metabolism derived TCR ligands for innate immunotherapy of liver cancer

Introduction: Mucosal-associated invariant T (MAIT) cells are an abundant T cell subset in the human liver and they play a crucial role in the regulation of immunity and inflammation. MAIT cells can be activated and expanded using riboflavin metabolism-derived T cell receptor (TCR) agonists. The aim of this work was to resolve the underlying mechanisms of MAIT-mediated anti-tumor immunity in human and mouse.

Methods: Ex vivo co-culture systems and cytotoxicity assays were used to investigate the effect of riboflavin-derived TCR-ligands on human circulating and hepatic MAIT cells. Syngeneic mouse models of orthotopic primary liver cancer and liver metastases were used to study anti-tumor activity of MAIT cells. A series of pharmacological depletion experiments were used to identify additional effector immune cells and humoral factors that mediate this effect in vivo. Single-cell RNA sequencing and high-dimensional flow cytometry provided crucial clues to underlying mechanisms.

Results: We show that MAIT cells are potent mediators of this anti-tumor activity across various models of liver cancer in vivo and in vitro when activated by distinct MAIT TCR-ligands. Sequencing and flow cytometry identified co-stimulatory effector molecules as critical components required for MAIT-induced tumor suppression. Additional pharmacological depletion experiments and genomic conditional knockout mouse strains helped to identify additional effector cells.

Conclusion: MAIT cells play an important role in tumor immunology and represent an attractive new target for immunotherapy. Finely tuned, context-dependent mechanisms determine MAIT cell function in vivo and in vitro.

Publication History

Article published online:
04 September 2025