Vitamin D receptor gene Tru9I polymorphism and risk for incidental sporadic colorectal adenomas

AIM： Recent laboratory and epidemiological studies suggest that vitamin D is a potential agent for colorectal cancer prevention. Its function is partially mediated by the vitamin D receptor （VDR）. The aim of this study was to investigate whether a novel G （allele ‘U’g〉A （allele ‘u’ polymorphism （Tru9I） in the VDR intron 8 region is associated with risk for colorectal adenoma in a colonoscopy-based case-control study. METHODS： Genotyping for a total of 391 subjects was carried out through PCR and restriction fragment length polymorphism. RESULTS： The frequencies of ‘U’ and ‘u’ alleles were 89.3% and 10.7%, respectively. The ‘Uu’ and ‘uu’ genotypes were associated with decreased risk for adenoma （OR, 0.71; 95%CI, 0.40-1.25）. The inverse association was more pronounced for multiple adenomas and adenomas that were larger had moderate or greater dysplasia, or were sessile： the odds ratios （ORs） were, 0.51 （95%CI, 0.21-1.24）, 0.37 （95%CI, 0.11-1.28）, 0.68 （95%CI, 0.33- 1.41）, and 0.36 （95%CI, 0.13-0.97） respectively. In joint/ combined analyses, inverse associations were more obvious among those who had at least one ‘u’ allele and also were younger （OR, 0.60; 95%CI, 0.26-1.37）, women （OR, 0.38; 95%CI, 0.17-0.88）, did not smoke （OR, 0.39; 95%CI, 0.13-1.23）, or took NSAID （OR, 0.38; 95%CI, 0.12-1.25）, but no evidence existed for interactions with calcium or vitamin D intake.CONCLUSION： Our findings suggest that the VDR TrugI polymorphism may be associated with lower risk for colorectal adenoma, particularly in interaction with various risk factors, but not with calcium or vitamin D.

Novel genetic variations of the p53R2 gene in patients with colorectal adenoma and controls

AIM: p53-Inducible ribonucleotide reductase small subunit 2 (p53R2) encodes a 351-amino-acid peptide, which catalyzes conversion of ribonucleoside diphosphates to the corresponding deoxyribonucleotides required for DNA replication and repair. A recent study reported that a point mutation (G/T) in the p53 binding sequence in a colon cancer cell line completely impaired p53R2 protein activity.METHODS: We screened the p53R2 gene coding regions and a regulatory region which contains a p53 binding sequence in 100 patients with colorectal adenoma and 100 control subjects using PCR, cold SSCP, and direct DNA sequencing.RESULTS: Although we did not identify genetic variation in all nine exons, four regulatory-region variants were found,of which three were single nucleotide polymorphisms (SNPs) (nt 1 789 C/G, nt 1 928 A/G, 1 933 T/C), and one was 20 bp insertion which replaced a ATTTT between nt 1 831 and 1 835. Additionally, we determined the frequency of these p53R2 variants in a recently concluded case-control study of incident sporadic colorectal adenomas (163 cases and 210 controls).CONCLUSION: Although more detailed functional characterizations of these polymorphisms remain to be undertaken, these polymorphic sites may be useful for identifying alleles associated with mis-splicing, additional transcript factors and, more generally, in cancer-susceptibility association studies.