Downregulation of Dicer, a component of the microRNA machinery, in bladder cancer.

Dysregulation of microRNA metabolism has been observed in a variety of human cancers. In this study, we evaluated the expression of the enzymes of the machinery Dicer, Drosha and DGCR8, in transitional cell carcinomas (TCCs) of the urinary bladder. The expression of Dicer, Drosha and DGCR8 was analyzed using semi-quantitative RT-PCR in clinical specimens from normal bladder mucosa, TCCs and their normal adjacent tissues (NATs). Immunohistochemistry was performed to compare the expression of Dicer in normal, TCCs and NATs. Our study demonstrated that Dicer mRNA levels in TCCs were significantly lower compared to normal samples and NAT samples. The immunohistochemistry results revealed that Dicer protein levels in TCCs were significantly downregulated compared to normal bladder mucosa and NATs. Our data demonstrated that Dicer is significantly downregulated in TCCs compared to paired NAT samples and normal samples, suggesting that reduced expression of Dicer may play an important role in bladder cancer.