Standard chemotherapeutic drugs may promote immune evasion by activating the KP; in HNSCC cells, cetuximab induces IDO1, and in melanoma, the anti‐PD1 monoclonal antibody (mAb) nivolumab can induce IL4I1 and IDO1, with nivolumab treatment linked to AhR activation. Here, IDO1 is linked to head and neck squamous cell carcinoma.