METTL3/CD98-mediated glutamate efflux in CAFs drives CD8+ T cell exhaustion and impedes neoadjuvant immunochemotherapy

The role of neurotransmitters in suppressing anti-tumor immunity has garnered increasing attention. While glutamate has been extensively studied in neurological diseases, its potential role in regulating anti-tumor immunity, particularly in the context of neoadjuvant immunochemotherapy, remains underexplored. In this study, we find that glutamate levels are elevated in the plasma of head and neck squamous cell carcinoma (HNSCC) patients. The METTL3/m6A/CD98 axis in cancer-associated fibroblasts (CAFs) is a key driver of glutamate secretion. Glutamate induces CD8⁺ T cell exhaustion through SLC1A3 and impairs the formation of immune memory in secondary lymphoid structures. Additionally, glutamate promotes ferroptosis resistance in HNSCC. Notably, glutamate depletion enhances the efficacy of neoadjuvant immunochemotherapy. Our findings provide insights into how the METTL3/m6A/CD98 axis-mediated regulation of glutamate efflux may sensitize HNSCC to neoadjuvant immunochemotherapy.