AXIN2 and lung cancer: Stratified analysis by cancer types indicated that the AXIN2 rs2240308 polymorphism increases the risk of lung cancer (G allele vs. A allele: OR = 1.36, 95 % CI = 1.17–1.59; GA vs. AA: OR = 1.43, 95 % CI = 1.01–2.02; GG vs. AA: OR = 1.93, 95 % CI = 1.36–2.75; GG + GA vs. AA: OR = 1.65, 95 % CI = 1.18–2.30; GG vs. GA + AA: OR = 1.45, 95 % CI = 1.18–1.79.