Upregulation of CXCR4 expression in gastric cancer cells by TNF-α. (A) and (B) CXCR4 expression was upregulated in MKN45 cells by exogenous TNF-α in a dose-dependent manner, *P < 0.01. (C) and (D) The coculture system of MKN45 and RAW264.7 cells expressed more CXCR4, *P < 0.001, vs M; **P < 0.001, vs R. The upregulation of CXCR4 expression was inhibited after treatment with infliximab, ***P < 0.001, vs M + R + inf. M: MKN45; R: RAW264.7; inf: infliximab. (E) Expression of TNF-α was absent in HGC27 cells after transfection with TNF-α RNAi plasmid. (F) CXCR4 mRNA expression was downregulated in HGC27 cells after transfection with TNF-α RNAi plamid, *P < 0.001, vs No RNAi; **P < 0.001, vs Control RNAi. Data are expressed as mean ± SD, n = 3.