In all five PCA models for lung cancer were constructed using the marker expression as variables (CXCL12, CXCR4, CK7, CDH1, CTNNB1, CLDN4, HIF1A, VEGFA, MMP9, MUC16, TGFBR2, TP53, OPN, CDKN2A, and CD44v6) as shown in Fig 3. The gene discussed is CLDN4; the disease is lung carcinoma.