AIM:To investigate the association of the inducible nitric oxide synthetase(iNOS) C150T polymorphism with Helicobacter pylori(H.pylori) infection and gastric cancer(GC) risk in Iran.METHODS:In order to determine whether there was a correlation between iNOS genotype and GC in Iran,we conducted a case-control study using samples from 329 individuals.For each sample,the C150T iNOS polymorphism was genotyped by polymerase chain reaction(PCR) and restriction digestion.Patients were grouped by cancer presence,demographic and behavior characteristics,and H.pylori infection status.Statistical tests were conducted to determine whether any behavioral factors or a particular iNOS genotype was associated with GC in the study population.RESULTS:In this population,we found that smoking,hot beverage consumption,a familial history of GC and H.pylori infection status were significantly associated with GC development(P = 0.015,P < 0.001,P = 0.0034,and P < 0.015,respectively).The distribution of the C150T iNOS genotypes among the two study groups was not statistically significant alone,but was impacted by H.pylori infection status.When compared to the non-H.pylori infected group,cancer patients who had a heterozygous CT genotype and were also infected with H.pylori were 2.1 times more at risk of developing GC [odds ratio(OR) = 2.1,P = 0.03] while those with a homozygous TT genotype and infected with H.pylori were 5.0 times more at risk of developing GC(OR = 5.0,P = 0.029).In contrast,this association was not seen in patients in the control group.CONCLUSION:A CT or TT polymorphism at position 150 in the iNOS gene significantly increases the risk of GC and may be a marker for GC susceptibility. AIM: To investigate the association of the inducible nitric oxide synthetase (iNOS) C150T polymorphism with Helicobacter pylori (H. pylori) infection and gastric cancer (GC) risk in Iran. METHODS: In order to determine whether there was a correlation between iNOS genotype and GC in Iran, we conducted a case-control study using samples from 329 individuals. For each sample, the C150T iNOS polymorphism was genotyped by polymerase chain reaction (PCR) and restriction digestion. Pats were grouped by cancer presence, demographic and behavior characteristics , and H. pylori infection status. Statistical study were conducted to determine whether any behavioral factors or a particular iNOS genotype was associated with GC in the study population .RESULTS: In this population, we found that smoking, hot beverage consumption, a familial history of GC and H. pylori infection status were significantly associated with GC development (P = 0.015, P <0.001, P = 0.0034, and P <0.015, respectively) T iNOS genotypes among the two study groups was not significant significant, but was was impacted by H. pylori infection status. When compared to the non-H. pylori infected group, cancer patients who had a heterozygous CT genotype and were also infected with H .pylori were 2.1 times more at risk of developing GC [odds ratio (OR) = 2.1, P = 0.03] while those with homozygous TT genotype and infected with H. pylori were 5.0 times more at risk of developing GC (OR = 5.0 , P = 0.029) .In contrast, this association was not seen in patients in the control group. CONCLUSION: A CT or TT polymorphism at position 150 in the iNOS gene significantly increases the risk of GC and may be a marker for GC susceptibility.