We found that CLDN1 knockdown increased sphere formation (only the CSCs can form the sphere; Figure 3A), SLUG expression (in sphere culture condition; Figure S3B), and stemness markers including ALDH1A1, NANOG, NES, and OCT4; notably, ALDH1A1, aldehyde dehydrogenase (ALDH) 1 family member A1, (also prognostic and stemness marker for lung adenocarcinoma) 45, 46 was upregulated to a greater extent than the other markers (Figure 3B). This evidence concerns the gene CLDN1 and lung adenocarcinoma.