Objective: To investigate the polymorphisms of interleukin-1B (IL-1B) promotor region 31 C/T and interleukin-1 receptor antagonist (IL-1RN) gene and the relationship between the genotype of IL-1 and IL-1RN and susceptibility to gastric cancer in Chinese population.
Methods: Genomic DNA was extracted from the juxta-cancerous normal mucosal biopsies of 50 patients with gastric cancer taken by endoscopy and from the peripheral lymphocytes of 50 normal controls and then was subjected to PCR amplification. The PCR product was digested by restriction endonuclease Alu I. The product of digestion was subjected to 2% agarose gel electrophoresis and ethidium bromide staining.
Results: The IL-1B -31C allele was detected in 75% of normal controls and 53% of patients, while the IL-1B -31T allele was detected in 25% of normal controls and 47% of patients. The frequency of -31C/-31C was 56% (28/56) and 30% (15/50) in normal controls and patients respectively. The frequency of -31C/-31T was 38% (19/56) and 46% (23/50) in normal controls and patients respectively. The frequency of -31T/-31T was 6% (3/56) and 24% (12/50) in normal controls and patients respectively. IL-1B -31T carriers were at increased risk of gastric cancer with an odds ratio of 7.5 for -31T/-31T homozygotes (95% CI, 2.0 approximately 27.6) and of 2.3 for -31C/-31T (95% CI, 0.9 approximately 5.4) respectively. Only three of the five kinds of polymorphism of IL-1RN (1/1, 1/2 and 2/2) were found in this study. The frequency of 1/1 was 54% (27/50) and 24% (12/50) in normal controls and patients respectively. The frequency of 1/2 was 38% (19/50) and 50% (25/50) in normal controls and patients respectively. The frequency of 2/2 was 8% (4/50) and 26% (13/50) in normal controls and patients respectively. The IL-1RN * 1 allele was detected in 73% of normal controls and 49% of patients; while the IL-1RN * 2 allele was detected in 27% of normal controls and 51% of patients. IL-RN * 2 carriers were at increased risk of gastric cancer with an odds ratio of 7.31 for 2/2 homozygotes (95% CI 2.13 approximately 25.09) and of 2.96for 1/2 heterozygotes (95% CI 1.22 approximately 7.21), respectively.
Conclusion: The polymorphism of promotor region -31C/T of IL-1B gene and the polymorphism of IL-1RN genes 1/2 and 2/2 are associated with the susceptibility of gastric cancer in Chinese. Carrying -31T allele increases the risk of gastric cancer. Polymorphism of IL-1RN and IL-1B gene may be used as indicators of susceptibility of gastric carcinogenesis.