COL4A5 and gastric cancer: Collagen alpha-2 (I) chain (COL1A2) and secreted factor S100 calcium binding protein A6 (S100A6) were found upregulated in GC, whereas downregulated proteins included collagen alpha-5 (VI) chain (COL6A5) and collagen alpha-3 (VI) chain (COL6A3), heparan sulfate proteoglycan 2 (HSPG2), lumican (LUM), laminin subunit gamma-1 (LAMC1) and secreted factor stromal cell-derived factor 1 (CXCL12), along with COL4A5, WNT2B, NID1, OGN, AMBP and DCN, which had been already identified when comparing tumor with normal distant mucosa.