The mRNA level of CLDN1 in A549 cells derived from lung adenocarcinoma, RERF-LC-AI cells derived from squamous cell carcinoma, IA-LC cells derived from large cell carcinoma, and WA-hT cells derived from small cell carcinoma were higher than that in normal tissue (Figure 1B). The gene discussed is CLDN1; the disease is lung adenocarcinoma.