MAPK1 and gastric cancer: ERK rs5999749, Dock180 rs4635002 and C3G rs7853122 showed significant gene-dose effect for gastric cancer (OR = 1.40, [95% CI: 1.04–1.89]; OR = 0.65, [95% CI: 0.44–0.94]; OR = 0.61, [95% CI: 0.46–0.81], respectively).