HIF1A and gastric cancer: When further stratifying the TNM stage, HIF-1α expression of patients with stages III and IV gastric cancer was much higher than those with stage I and II gastric cancer in 10 studies (1274 patients; OR  = 2.762, 95% CI  = 1.941–3.942, P<0.001), without significant between-study heterogeneity (I2 = 48.4%, subgroup difference P = 0.042) (Table 2).