Accordingly, we addressed tumor heterogeneity by investigating cells harboring major mutations that are commonly found in lung adenocarcinoma, utilizing H1975 (EGFR L858R and T790M), PF901 (BRAF V600E), PF139 (KRAS G12C), and H838 (triple wild type with no known driver mutation) cell lines. The gene discussed is EGFR; the disease is lung adenocarcinoma.