There were 8 overexpressed FDGs, including PSAT1, FADS1, MFAP5, LDLR, COL4A1, COL4A2, MCAM, and KRT14 (four in state 1 and four in state 2), and 2 downregulated FDGs, including HP and CFB (all in state 3), in metastatic tumors (Additional file 1: Fig. S8B). The gene discussed is COL4A1; the disease is metastatic neoplasm.