OBJECTIVE: To investigate single nucleotide polymorphisms(SNPs) and haplotypes of interleukin-18(IL-18) gene associated with the susceptibility to colorectal cancer(CRC). METHODS: Two SNPs of IL-18 gene promoter -137G/C and -607C/A in 170 patients with CRC and 160 healthy controls matched by age and sex in a Chinese population were analyzed using polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) strategy. Frequency of haplotypes and linkage disequilibrium of IL-18 gene in different groups were analyzed by SHEsis programs. RESULTS: The distributions of IL-18 gene -607C/A polymorphism did not differ between CRC patients and healthy controls, but IL-18 gene -137G/C polymorphism was significantly different(P<0.05). The relative risk of C allele for CRC was 1.814 times of the G allele (OR=1.814,95% CI:1.246-2.642). Consistent with the results of the genotyping analyses, IL-18 -137G/C and -607C/A polymorphisms showed strong linkage disequilibrium(|D'|=0.945), frequency of the -137C/-607A haplotype in patients with CRC was significantly higher than that in healthy controls(P<0.05). The -137C/-607A haplotype was associated with a significantly increased risk of CRC(OR=1.637, 95% CI:1.100-2.437). CONCLUSIONS: IL-18 gene -137G/C polymorphism and -137C/-607A haplotype are associated with CRC. -137C allele may be an important genetic susceptibility gene for CRC.
OBJECTIVE: To investigate single nucleotide polymorphisms(SNPs) and haplotypes of interleukin-18(IL-18) gene associated with the susceptibility to colorectal cancer(CRC). METHODS: Two SNPs of IL-18 gene promoter -137G/C and -607C/A in 170 patients with CRC and 160 healthy controls matched by age and sex in a Chinese population were analyzed using polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) strategy. Frequency of haplotypes and linkage disequilibrium of IL-18 gene in different groups were analyzed by SHEsis programs. RESULTS: The distributions of IL-18 gene -607C/A polymorphism did not differ between CRC patients and healthy controls, but IL-18 gene -137G/C polymorphism was significantly different(P<0.05). The relative risk of C allele for CRC was 1.814 times of the G allele (OR=1.814,95% CI:1.246-2.642). Consistent with the results of the genotyping analyses, IL-18-137G/C and -607C/A polymorphisms showed strong linkage disequilibrium(|D'|=0.945), frequency of the -137C/-607A haplotype in patients with CRC was significantly higher than that in healthy controls(P<0.05). The -137C/-607A haplotype was associated with a significantly increased risk of CRC(OR=1.637, 95% CI:1.100-2.437). CONCLUSIONS:IL-18 gene -137G/C polymorphism and -137C/-607A haplotype are associated with CRC. -137C allele may be an important genetic susceptibility gene for CRC.