Indeed, in addition to RKO, A375 (melanoma, PD-L1 weakly positive), A431 (epidermoid carcinoma, PD-L1 negative), QGP-1 (pancreatic islet cell carcinoma, PD-L1 negative), or A549 (lung adenocarcinoma, PD-L1 weakly positive) were resistant to nivolumab among the cell lines we preliminary tested (data not shown). Here, CD274 is linked to squamous cell carcinoma.