IL6 and gastric cancer: The 61 studies included compared TNF-α, TNF-β, IFN-r, CCL-2, CCL-5, CCL-18, CCL-20, CXCL-8, CXCL11, CXCL12, CXCL13, IL-1a, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-11, IL-12, IL-13, IL-15, IL-16, IL-17, IL-18, IL-23, IL-24, IL-26, IL-29, IL-32, IL-35, IL-37, TGF-β, TGF-β1, TGF-β2, IFN-λ1 and IFN-λ2/3 serum cytokine levels between GC patients and controls (Supplementary Table S8).