COL4A1 and gastric cancer: Furthermore, the UALCAN results discerned that the expression pattern of the hub genes, including COL1A1, COL1A2, TIMP1, SPP1, COL5A2, THBS2, COL4A1, CXCL8, and BGN, were significantly higher in GC stages I–IV than normal samples, whereas MUC6 was significantly downregulated in different stages of GC (Fig. 7).