DNMT3B and head and neck cancer: In the stratified analysis by cancer type, DNMT3B −149C/T polymorphism was relative with a significantly increased risk of head and neck cancer in two tested models (CT vs. TT: OR 0.73, 95 % CI 0.59–0.9; P = 0.33, I2 = 0 % for heterogeneity; CC/CT vs. TT: OR 0.76, 95 % CI 0.61–0.93; P = 0.3, I2 = 7 % for heterogeneity; Fig. 1).