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. Here, MMP9 is linked to lung cancer.