Additionally, F. nucleatum-derived outer membrane vesicles contribute to immunotherapy resistance in head and neck squamous cell carcinoma (HNSCC) by altering tryptophan metabolism in TAMs, activating the TDO2/AhR pathway, and promoting transcriptional upregulation of immunosuppressive cytokines and checkpoint molecules [154]. Here, AHR is linked to head and neck squamous cell carcinoma.