Overall, in our study ACE I/D, NOD1 796G>A, TLR4 3725G>C, FAS 1377G>A, FAS 670A>G and FASL 844T>C gene polymorphisms were not associated with the presence of GC or HRAG. Here, we evaluated six genetic polymorphisms related to the immune-recognition of H. pylori, proliferation and apoptosis that were previously described to be associated with increased risk of GC or premalignant gastric lesions in different case-control studies; however reported data are partially conflicting or just based on one study [11–14, 20, 21, 26, 33–35]. Since ACE, NOD1, TLR4, FAS, and FASL have been shown to be involved in gastric carcinogenesis pathways, we expected that the polymorphisms of genes encoding these proteins could be related to GC.
When analyzing ACE I/D polymorphism we hypothesized that carriers of D allele, which was associated with higher ACE activity , could have an increased risk of GC. Ebert et al.  identified an association of ACE D/D genotype with the development of early GC, and the same group of researchers showed that this genotype is related to the number of metastatic lymph nodes in GC, but not to the overall risk for GC in German subjects . A Japanese study did not find an association between ACE I/D polymorphism and suseptibility to GC . Another Asian study  reported that ACE I/D polymorphism carried a higher risk for GC with odds ratio of 1.59, however the same study did not find significant association of ACE polymorhisms with gastric atrophy. ACE I/D genotype frequencies in our study are in line with previous reports . We did not observe significant link between ACE I/D polymorphisms and the risk for GC or HRAG.
Considering the relationship between H. pylori-induced chronic inflammation and carcinogenesis in the stomach it was tempting to speculate that genetic variation in NOD1 receptor, which is involved in bacterial recognition, could be associated with H. pylori-induced diseases. NOD1 796A/A homozygous mutants were linked with increased risk for peptic ulcer disease in a Hungarian study ; however they did not find a significant association with atrophic gastritis. A recent study from Turkey  found that subjects with NOD1 796A/A genotype had a significantly increased risk for gastric atrophy and antral intestinal metaplasia with very high odds ratios, 34.2 and 39.7 respectively. Such a strong association reported by Kara et al.  urged us to evaluate the possible association of this polymorphism in our subjects with GC and HRAG. The genotype frequencies of NOD1 796G>A in this study correspond to previous reports [20, 21]. In our study we observed a tendency for NOD1 796G/G genotype and allele G for increased risk for atrophic gastritis; however the difference did not reach statistical significance. We did not observe an association between NOD1 796G>A gene polymorphism and HRAG or GC. H. pylori seropositivity status was also not linked with NOD1 796G>A genotypes.
Polymorphisms of TLR4 gene are hypothesized to decrease responsiveness to gram-negative bacteria lipopolysaccharide through alterations in binding. In a recent study TLR4 3725G>C polymorphism was indentified as a risk factor for severe gastric atrophy in H. pylori sero-positive Japanese subjects with OR of 1.43 and 1.47 for G/C and C/C genotypes, respectively , however in the same study this polymorphism was not associated with the risk for GC. Another study showed a combined effect of TLR4 3725G>C and miR-146a G>C gene polymorphisms for risk of gastric atrophy, but not for GC . Our data on TLR4 3725G>C genotype frequencies are comparable to the reported frequencies in leukemia study on Caucasian population . We did not find significant association between TLR4 3725G>C genotypes and HRAG or GC. There was also no association between H. pylori seropositivity and TLR4 3725G>C genotypes.
There are only few studies that have evaluated the risk for GC in relation to FAS and FASL gene polymorphisms. Reported results are conflicting and cover Asian subjects only. In two Chinese case-control studies FAS and FASL genotypes had no significant associations with risk of GC [33, 34]. Another study from China suggested that FASL 844T/T or T/C and FAS 1377A/A genotypes could be a risk factor for GC in combination with other gene polymorphisms . Hsu et al.  have reported that FAS 1377 allele A was a protective factor for developing intestinal metaplasia in the antrum with odds ratio 0.3, while carrying the FASL 844 allele C was a risk factor for developing gastric atrophy in the corpus with OR of 9.4. The distribution of FAS and FASL genotypes in our cohorts corresponds to the frequencies reported on Caucasian subjects in a lung cancer study , but we could not provide any evidence that FAS and FASL gene polymorphism are linked with risk for GC or HRAG in Caucasians.
In the present study we evaluated potential links between the risk for GC and several carcinogenesis-related gene polymorphisms that have been rarely or not described, especially in Caucasian population. We did not find significant associations between the presence of GC or HRAG and ACE I/D, NOD1 796G>A, TLR4 3725G>C, FAS 1377G>A, 670A>G and FASL 844T>C gene polymorphisms. We also analyzed the genotype frequencies with respect to different histological GC types. ACE D/D genotype was less prevalent in diffuse-type GC than in controls, however the corresponding subgroups of intestinal and diffuse-type GC are rather small are therefore firm conclusions can not be drawn. Because the studies on ACE I/D, NOD1 796G>A, TLR4 3725G>C, FAS 1377G>A, 670A>G and FASL 844T>C polymorphisms remain limited, evaluation of the association with GC and premalignant gastric lesions requires additional research. Since the strength of the association may depend on the studied population, larger studies of different ethnic groups with different genetic profiles are required. The differences in current data on these polymorphisms may result from study design, H. pylori prevalence, and different histological subtypes of GC. In this study there was no difference in H. pylori positivity among GC, HRAG and control groups. The possible explanation for these findings could be higher prevalence of H. pylori in Baltic countries, when compared to Germany. HRAG and control groups were selected both in Germany and Baltic countries, while GC subjects were recruited only in the German centre, thus possibly affected the H. pylori status within the groups. Alterations in various genes, including oncogenes, tumor-suppressor genes, proinflammatory genes, bacterial recognition and cell-adhesion-related genes have been studied in gastric carcinogenesis [5, 24, 46]. In previous studies we also evaluated the role of IL-1B, IL-1RN and NOD2 gene polymorphisms with respect to risks for GC; however no significant associations were identified [36–38]. Some reports suggested that host genetic factors determine the severity of gastric damage and the eventual clinical outcome of H. pylori infection [47, 48]. These findings however have not been transferred to daily clinical practice, and therefore applicable predisposing genetic factors remain still to be determined.