Ph.D. candidate University of Texas at San Antonio, Texas, United States
Disclosure(s):
Ariel R. Laub: No financial relationships to disclose
Introduction/Rationale: Mucosal-associated invariant T (MAIT) cells recognize microbially derived metabolite antigens presented by MHC-related protein 1 (MR1), yet their activation and cytotoxicity against cancer cells are not well defined. We hypothesized that tumor-associated nucleoside adducts serve as MR1 ligands that activate MAIT cells and enable killing of glioblastoma (GBM) and other cancer cells.
Methods: Here, we examined MR1-dependent MAIT cell killing of various cancer cell lines, including myelogenous leukemia cell K562, and glioblastoma cells U87, U251, and A-172. Human polyclonal MAIT cells (Vα7.2⁺CD161^hi) were co-cultured with cancer cells, with candidate nucleoside adducts added as putative stimulatory MR1 ligands. MAIT activation was quantified by IFN-γ ELISpot counts. Tumor cell death was assessed in MAIT–GBM co-cultures by fluorescent confocal microscopy using propidium iodide (PI). LC–MS/MS of GBM cell eluates evaluated endogenous presence of the candidate nucleoside adduct. Appropriate vehicle/unstimulated controls and statistical comparisons were included.
Results: We identified nucleoside adducts and other derivatized metabolites that stimulated MAIT cells, as evidenced by increased IFN-γ ELISpot responses relative to unstimulated controls. MR1-blocking antibodies markedly reduced IFN-γ production, supporting MR1-dependent MAIT cell activation mediated by nucleoside adducts. Functionally, exposure of A-172 glioblastoma cells to polyclonal MAIT cells stimulated by candidate ligands increased tumor cell death as visualized by fluorescent confocal microscopy. Mass spectrometry of GBM cell eluates detected the candidate nucleoside adduct, indicating endogenous production by tumor cells.
Conclusion: Together, these data implicate an MR1–nucleoside adduct axis in MAIT recognition of cancer-associated metabolites and support the potential of MAIT-directed, MR1-restricted therapeutic strategies for glioblastoma and other cancers.
