Genetic susceptibility to ulcerative colitis in the Chinese Han ethnic population: association with TNF polymorphisms

BACKGROUND: Tumor necrosis factor alpha (TNFalpha) is an important proinflammatory cytokine that has been implicated in the pathogenesis of inflammatory bowel disease (IBD). Recent studies have evaluated the role of TNF promoter polymorphisms in IBD, whereas the data are inconsistent. Trans-racial mapping in an ethnically distinct but homogenous population may help clarify these associations. We investigate the association between TNF promoter polymorphisms and susceptibility to ulcerative colitis (UC) in the Chinese Han ethnic population. METHODS: We studied 110 unrelated UC patients and 292 healthy controls from Zhejiang Province, China. Genotyping for 6 common TNF promoter polymorphisms (TNF -1031T/C, -863C/A, -857C/T, -380G/A, -308G/A, -238G/A) was carried out by polymerase chain reaction sequence-specific primers (PCR-SSP). RESULTS: TNF -308A was associated with disease (allele frequency patients 14.6% vs controls 8.9%, P = 0.02). TNF -857T was increased in patients but without statistical significance (allele frequency 17.3% vs 12.2%, P = 0.06). Haplotype analysis revealed 6 haplotypes including two (H5 and H3), which contained TNF -308A. H5 was associated with disease (haplotype frequency patients -12.3% vs controls 7.5%, P = 0.03). Of note the rare haplotype H3 has not previously been identified in Caucasian populations. Homozygosity for the haplotype H4 comprising the common alleles at each TNF promoter single-nucleotide polymorphism (SNP) was negatively associated with disease (patients vs controls 24.5% vs 34.9%, P < 0.05). CONCLUSIONS: We report the association with TNF -308A polymorphisms in Chinese patients with ulcerative colitis. The functional study in Chinese Han ethnic population is now required.