Association of interleukin 1B gene polymorphism and gastric cancers in high and low prevalence regions in China.
AIM
Our aim was to study the relationship between interleukin 1B (IL-1B) polymorphism, Helicobacter pylori infection, and gastric cancer in high prevalent (Shanxi) and low prevalent (Guangdong) regions in China.


METHOD
Genomic DNA was extracted from peripheral blood of 192 healthy volunteers, 84 gastric cancer patients from Guangdong and 169 healthy volunteers, and 86 gastric cancer patients from Shanxi. Polymorphisms in IL-1B that encodes IL-1beta and IL-1RN that encodes IL-1 receptor antagonist were analysed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). These polymorphic sites include promoter regions of IL-1B at positions +3954, -511 (C-T transition), and -31 (T-C transition), and IL-1RN variable tandem repeats.


RESULTS
In the low prevalence region, the frequencies of the IL-1B +3954 T/T and IL-1RN *2/*2 genotypes were similar. IL-1B -511T/T genotype frequency was significantly higher among patients with gastric cancer (25.0%) than control subjects (12.5%) (chi2=6.7, p=0.01). In the high prevalence region, the frequencies of the IL-1B +3954T/T and -511T/T genotypes and the IL-1RN *2/*2 genotype in the cancer and control groups were similar. IL-1B -31C/C genotype frequency was significantly higher among patients with gastric cancer (90.0%) than controls (78.0%) (chi2=5.0, p=0.025). Compared with the low prevalence region, control subjects from the high prevalence region had a higher frequency of the IL-1B -511T/T genotype (23.0% v 12.5%; chi2=7.0, p<0.008). While H pylori infection alone had only a modest effect on the risk of gastric cancer development (odds ratio (OR) 5.0 (95% confidence interval (CI) 1.5-16.3)), combined with the IL-1B -511T/T genotype the risk was markedly elevated (OR 17.1, 95% CI 3.8-76.4).


CONCLUSION
IL-1B -511T/T genotypes are associated with gastric cancer in China. The effect of IL-1B polymorphism is less obvious in areas of high prevalence for gastric cancer.