The role of aberrant promoter hypermethylation of DACT1 in bladder urothelial carcinoma

The purpose of this study was to determine the relationship between hypermethylation of DACT1 gene pro-moter and lower mRNA expression in bladder urothelial carcinoma tissue.The methylation status of 29 urothelial carcinoma samples and 29 normal tissue samples were examined by methylation-specific polymerase chain reac-tion（MSP）.The DACT1 mRNA transcript levels and DACT1 protein levels in all samples were then evaluated to define the relationship between the methylation status of the DACT1 promoter and its expression at the transcrip-tional and translational levels.Decreased expression of DACT1 was detected in 89.66% of urothelial carcinomas（26/29;P 〈 0.005）.Promoter hypermethylation was found in 58.62%（17/29） urothelial carcinomas and 25%（7/29） normal tissues,respectively（P 〈 0.05）.DACT1 expression was lower in tissues where the DACT1 gene promoter was hypermethylated than in unmethylated tissues（0.25±0.17 vs 0.69±0.30,P 〈 0.05）.DACT1 gene hyper-methylation was closely related to tumor size,grade and stage（P 〈 0.05）.Our results indicate that silencing and downregulation of DACT1 mRNA may be implicated in carcinogenesis and the progression of bladder urothelial carcinoma,and may be a potential prognostic factor.

MTHFR C677T polymorphisms are associated with aberrant methylation of the IGF-2 gene in transitional cell carcinoma of the bladder

The purpose of this study was to determine the relationship between methylation status of the insulin-like growth factor 2 （IGF-2） gene and methylenetetrahydrofolate reductase （MTHFR） C677T gene polymorphisms in bladder transitional cell carcinoma tissues in a Chinese population. The polymorphisms of the folate metabolism enzyme gene MTHFR were studied by restrictive fragment length polymorphism （RFLP）, PCR-based methods of DNA methylation analysis were used to detect the CpG island methylation status of the IGF-2 gene. The association between the methylation status of the IGF-2 gene and clinical characteristics, as well as MTHFR C677T polymorphisms, was analyzed. Aberrant hypomethylation of the IGF-2 gene was found in 68.3% bladder cancer tissues and 12.4% normal bladder tissues, respectively, while hypomethylation was not detected in almost all normal bladder tissues. The hypomethylation rate of the IGF-2 gene in cancer tissues was significantly higher in patients with lymph node metastasis than in those without lymph node metastasis （46.3% vs 17.2%, P = 0.018）. No association was found between aberrant DNA methylation and selected factors including sex, age, tobacco smoking, alcohol consumption and green tea consumption. After adjusting for potential confounding variables the variant allele of MTHFR C677T was found to be associated with hypomethylation of the IGF-2 gene. Compared with wildtype CC, the odds ratio was 4.33 （95% CI=1.06-10.59） for CT and 4,95 （95% CI=1.18-12.74） for TT. MTHFR 677 CC and CT genotypes might be one of the reasons that cause abnormal hypomethylation of the IGF-2 gene, and the aberrant CpG island hypomethylation of the IGF-2 gene may contribute to the genesis and progression of bladder transitional cell carcinoma.