The present study, therefore, hypothesizes that various activities of EGFR pathways associated with EGFR mutation and EGFR-TKI resistance could possibly change the expression levels of MMP-1 in EGFR-TKI–resistant lung adenocarcinoma and contribute to the development of EGFR-TKI resistance. The gene discussed is MMP1; the disease is lung adenocarcinoma.