CXCL8 and gastric cancer: Smoking is another risk factor for gastric cancer, as nicotine is strongly associated with gastric cancer metastasis by increasing IL-8 expression via the activation of ROS/NF-κB and ROS/MAPK (ERK 1/2, p38)/AP-1 axes in AGS gastric cancer cells, which stimulates angiogenesis and endothelial cell proliferation [115].