A549 is a wild‐type lung adenocarcinoma cell line, H1299 is a p53(−) lymph node‐metastatic lung adenocarcinoma cell line, H520 is a wild‐type lung squamous cell carcinoma cell line, H23 is a K‐ras and p53 mutant lung squamous cell carcinoma cell line, and SK‐MES‐1 is a cell line derived from pleural fluid from a patient with metastatic lung squamous cell carcinoma. The gene discussed is KRAS; the disease is lung adenocarcinoma.