Interleukin-8 gene expression in gastric tumors vs matched control mucosa. The solid line represents the relative ratio of IL-8 expression in tumor tissue compared to matched control gastric mucosa, as the log2 fold change (log2 tumor/control expression levels). A positive score indicates a higher expression in the tumor compared to the normal gastric mucosa. IL-8 was the most consistently up-regulated gene in the study. The grey background represents the expression of approximately 37 800 other genes.