Distribution of DT-diaphorase and reduced nicotinamide adenine dinucleotide phosphate: Cytochrome P450 oxidoreductase in bladder tissues and tumors

Purpose: We previously showed that mitomycin C activity in human bladder tu mors is inversely related to tumor stage and muscle invasive tumors are les s sensitive than superficial tumors. Because DT-diaphorase and reduced nico tinamide adenine dinucleotide phosphate: cytochrome P450 oxidoreductase (P4 50R) have a role in mitomycin C bioactivation, we investigated the distribu tion of these enzymes as a function of depth in the bladder wall and in hum an bladder tumors located at different parts of the bladder. Materials and Methods: Gene expression of DT-diaphorase and P450R relative to the expression of beta -actin was measured by reverse transcriptase-poly merase chain reaction in 4 dog and 8 human bladder tissue specimens, and in 46 human bladder tumors. DT-diaphorase activity was measured by enzymatic assay in dog and human bladders. Results: Data showed decreasing expression of DT-diaphorase and P450R from urothelium to muscle layer in the normal bladder wall with higher interindi vidual variation in humans than in dogs (greater than 40-fold versus approx imately 3-fold). The expression of DT-diaphorase and P450R in bladder tumor s correlated inversely with tumor stage (p < 0.05) and was significantly hi gher in superficial than in muscle invasive bladder disease. DT-diaphorase and P450R expression in bladder tumors was approximately 6-fold higher than in normal bladder tissue. In normal and tumor tissues DT-diaphorase expres sion correlated significantly with P450R (r(2) = 0.33, p <0.01), while DT-d iaphorase expression correlated with its enzyme activity (r(2) = 0.84, p < 0.01). Conclusions: Our results indicate a higher distribution of DT-diaphorase an d P450R in superficial bladder tumors and tissues. Preferential enzyme dist ribution in superficial tumors may be a cause of the higher efficacy of int ravesical mitomycin C therapy for superficial versus muscle invasive diseas e.