FAP and head and neck cancer: The lower levels of FAP expression and [111In]In-FAPI-46 uptake observed for PS-1 in vitro and U-87 MG ex vivo are most likely more representative for patients with FAP-positive CAFs infiltrating the tumors (e.g., colon, head and neck cancer, or non-small cell lung cancer), or U-87 MG even in vitro for cancer cells with FAP-expression (e.g., sarcoma, mesothelioma) [15], as it is questionable if the huFAP transduced models with homogeneous over-expression of FAP mimic the physiological expression levels of patients with these cancers.