Upon immunohistochemical analysis of EGFR-mutated NSCLC samples collected both before and after EGFR-TKI therapy, it was shown that MHC-I, the quantity of infiltrating CD8+ T-cells, phosphorylated EGFR, and ERK were all down-regulated, whilst PD-1 ligand one expression was up-regulated. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.