GSTM1 and gastric cancer: Furthermore, because the GSTM1 null genotype is regarded as a potential contributor to gastric cancer risk by influencing detoxification of activated environmental carcinogens and by interaction with unfavourable GSTT1 polymorphism, the possible modifying effects of GSTM1 status on the relationship between smoking status, alcohol drinking,Helicobacter pylori infection,GSTT1 polymorphism and gastric cancer risk is of great interest, even though not often investigated.