Since we found that MET+ mutant NSCLC patients seem to have higher PD-1, PD-L1 expression compared with the EGFR+ and KRAS+ mutant subgroups (Additional file 1: Figure S1), and high expression of c-MET and PD-L1 were detected in gefitinib resistant specimens (Fig. 1a), we investigated whether the upregulation of PD-L1 in these patients was related to the c-MET activation. Here, KRAS is linked to non-small cell lung carcinoma.