Identification of hepatocarcinogenesis-associated aldehyde dehydrogenase in normal rat urinary bladder.

An aldehyde dehydrogenase (ALDH) with properties identical to those of the NADP+-dependent, tumor-associated aldehyde dehydrogenase appearing during rat hepatocarcinogenesis has been identified in normal rat urinary bladder. Like the tumor-associated aldehyde dehydrogenase, bladder NADP+-ALDH is cytosolic and preferentially oxidizes benzaldehyde-like aromatic aldehydes. Bladder ALDH is also extremely sensitive to the aldehyde dehydrogenase inhibitor disulfiram. Additionally, the electrophoretic mobility of bladder ALDH is identical to that of the NADP+-dependent, tumor-associated aldehyde dehydrogenase. Finally, antibodies to the tumor-associated ALDH cross-react with bladder aldehyde dehydrogenase. Histochemically, bladder aldehyde dehydrogenase is localized to the very active epithelial lining and to the inner and outer smooth muscle layers. The observation that normal urinary bladder possesses an enzyme activity very similar to one expressed during hepatocarcinogenesis, but not in normal liver, is consistent with the hypothesis that derepression of a gene normally repressed in liver is responsible for expression of the tumor-associated aldehyde dehydrogenase phenotype.