High frequency of promoter methylation of the 14-3-3 sigma and CAGE-1 genes, but lack of hypermethylation of the caveolin-1 gene, in primary adenocarcinomas and signet ring cell carcinomas of the urinary bladder.

The molecular mechanisms underlying the histogenesis of nonurothelial carcinomas of the urinary bladder are not yet clearly understood. There is a growing body of evidence that, generally, epigenetic regulation mediated by methylation of normally unmethylated CpG islands at the 5' promoter regions of genes is involved in the modification of tumorigenesis. This prompted the current study to explore the methylation status of a broad panel of various genes implicated in cell differentiation and tumor suppression in 10 adenocarcinomas and 6 signet ring cell carcinomas of the bladder. Using methylation-specific PCR, we were able to detect a high frequency of promoter methylation of the 14-3-3 sigma (100%) and CAGE-1 (80%) genes in adenocarcinomas, and in nearly all signet ring cell carcinomas. The SYK and hDAB2IP genes proved to be hypermethylated in only single cases, whereas the caveolin-1 gene failed to be hypermethylated in all cases. The present data suggest that promoter methylation of the 14-3-3 sigma and CAGE-1 genes plays a crucial role during the phenotypical morphogenesis of vesical adenocarcinomas including signet ring cell carcinomas by an epigenetic mechanism.