Genetic polymorphism of glutathione S-transferases M1 and T1, tobacco habits and risk of stomach cancer in Mizoram, India

Abstract

Aim: The incidence of stomach cancer in Mizoram is highest in India. We have conducted a population based matched case-control study to identify environmental and genetic risk factors in this geographical area.

Methods: A total of 102 histologically confirmed stomach cancer cases and 204 matched healthy population controls were recruited. GSTM1 and GSTT1 genotypes were determined by PCR and H. pylori infections were determined by ELISA.

Results: Tobacco-smoking was found to be an important risk factor for high incidence of stomach cancer in Mizoram. Meiziol (local cigarette) smoking was a more important risk factor than other tobacco related habits. Cigarette, tuibur (tobacco smoke infused water) and betel nut consumption synergistically increased the risk of stomach cancer. Polymorphisms of GSTM1 and GSTT1 genes were not found to be directly associated with stomach cancer in Mizoram. However, they appeared to be effect modifiers. Persons habituated with tobacco smoking and/or tuibur habit had increased risk of stomach cancer if they carried the GSTM1 null genotype and GSTT1 non-null genotype.

Conclusion: Tobacco smoking, especially meiziol is the important risk factor for stomach cancer in Mizoram. GSTM1 and GSTT1 genes modify the effect of tobacco habits. This study is a first step in understanding the epidemiology of stomach cancer in Mizoram, India.