Classic bladder exstrophy and adenocarcinoma of the bladder: Methylome analysis provide no evidence for underlying disease-mechanisms of this association

Abstract

The bladder exstrophy-epispadias complex (BEEC) represents the severe end of uro-rectal malformation spectrum involving aberrant embryonic morphogenesis of the cloacal membrane and the urorectal septum. The most common form of BEEC is isolated classic bladder exstrophy (CBE). Long-term complications in CBE are malignancies of the bladder with 95% of them being adenocarcinomas. Since CBE and adenocarcinoma of the bladder are rare entities, their frequent co-occurrence suggests a common etiology. Recent studies suggest that promoter methylation of various genes play a crucial role during the phenotypical morphogenesis of adenocarcinomas of urinary bladder. To examine, whether epigenetic processes such as DNA methylation patterns are potentially associated with CBE, we performed Illumina 450 K methylation arrays in blood (n = 10) and tissue samples (n = 2) of CBE patients and healthy matched controls (n = 12). In our analysis, we found total lack of methylation in the blood and methylation differences were restricted to 10 CpG sites in the tissue samples. In comparison to other bladder anomalies, CBE tissue methylation profiles differ from those of adenocarcinoma, adenocarcinoma with CBE, urothelial carcinoma and urachal carcinoma. In this preliminary study, we did not provide any strong evidence of major DNA methylation alterations which would be suggestive for strong underlying epigenetic mechanism. However, larger studies are required to provide more robust statistical evidence to exclude smaller effects in the tissues.

Keywords: Adenocarcinoma of the urinary bladder; Classic bladder exstrophy; DNA methylation.