***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVES : Host genetic factors , including the IL1 gene cluster , play a key role in determining the long-term outcome of Helicobacter pylori infection . The aim of the study was to investigate the relationship between selected IL1 loci polymorphisms and  gastric cancer risk in an Italian population . METHODS : In a case-control study we compared the IL1B−31 and IL1B+3954 biallelic and IL1RN pentaallelic variable number of t and em repeats ( VNTR ) polymorphisms in 185 gastric cancer patients and 546 controls r and omly sample d from the general population of an area at high gastric cancer risk ( Tuscany , Central Italy ) . RESULTS : Genotype frequencies of the IL1B−31 T/C , IL1B+3954 C/T , and IL1RN polymorphisms among our population controls were in Hardy-Weinberg equilibrium . In multivariate analyses , no increase in gastric cancer risk was observed for the IL1B−31*C− and IL1B+3954*T− carriers ; a significant 50 % increase emerged for IL1RN*2 allele carriers ( OR = 1.49 ; 95 % CI : 1.01–2.21).Analyses based on combined genotypes showed also that the association with IL1RN*2 allele was limited to two-variant allele carriers who were also homozygous for the IL1B−31*T allele ( OR = 2.23 ; 95 % CI : 1.18–4.23 ) with a statistically significant interaction between these two genotypes ( p= 0.043 ) . Haplotype analysis showed an increased risk for the haplotype IL1RN*2/IL1B−31*T. CONCLUSIONS : Our results suggest that host genetic factors ( such as the IL1RN and the IL1B−31 polymorphisms ) interact in the complex process of gastric carcinogenesis in this high-risk Italian population . Overall , this effect appears more modest than previously reported in other population s , supporting the hypothesis that other still-to-be-defined factors are important in gastric carcinogenesis . These findings might be due to a haplotype effect Chronic inflammation is thought to contribute to the development of cancer ( [1][1 ] ) . Progressive inflammation leads to activation of inflammatory cytokines , recruitment of inflammatory cells , generation of free radical species , and subsequent malignant transformation . Individual responses to The proinflammatory cytokine interleukin-1 has been implicated in host susceptibility to Helicobacter pylori-associated disease . Recent studies suggest that this susceptibility may be under genetic control . It remains to be determined whether the relationship between IL-1 gene polymorphism and gastrointestinal disease in patients with H. pylori infection is due to the role of IL-1 in determining susceptibility to H. pylori infection per se or to the development of distinct pathological lesions . The aim of this study was to prospect ively investigate the relationship between selected polymorphisms in three of the major IL-1 gene family members , seeking associations with H. pylori infection and /or gastric cancer . A total of 559 individuals were studied : 191 patients attending for gastroscopy , 98 with current or previous H. pylori , an additional 79 patients with gastric cancer , and 289 healthy controls . The major novel finding of the study was a marked difference in the genotype frequencies for the IL1R1 HinfI SNP  in those with current or previous evidence of H. pylori compared to those without . ( GG , 53 vs 75 % ; GA , 40 vs 19 % ; AA , 7 vs 6 % ; P = 0.0079 ) . The association indicates an increased risk of H. pylori infection or persistence in those with the IL1R1 Hinf1 A allele ( 0.27 vs 0.156 ; P = 0.009 ; OR = 2.01 ) . Our results suggest that the relationship among IL-1 gene polymorphism , H. pylori , and disease is more complex than initially proposed . More detailed studies of the IL-1 gene cluster are needed 
    Output:
    
Results consistently supported increased cancer risk for IL1RN2 carriers ; the increased risk was specific to non-Asian population s and was seen for intestinal and diffuse cancers , distal cancers , and , to a lesser extent , cardia cancers .
Analyses restricted to high- quality studies or H. pylori-positive cases and controls also showed significant associations with both carrier status and homozygosity status .
In Asian population s , reduced risk was observed in association with IL1B-31C carrier status .
This effect was also observed in analyses restricted to high- quality studies .
These results indicate the importance of stratification by anatomic site , histologic type , H. pylori infection , and country of origin .