Correlation between the expression of P-glycoprotein and multidrug-resistant phenotype in transitional cell carcinoma of the urinary tract.

The expression of a multidrug-resistant (MDR) gene product, P-glycoprotein, was examined immunohistochemically in 41 transitional cell carcinomas (TCCs) of the urinary tract. In 23 of these, chemosensitivity to adriamycin (ADM) and vinblastine (VBL) was also assessed by a microtiter succinate dehydrogenase inhibition test and the correlation between the expression of P-glycoprotein and MDR phenotype was investigated. P-glycoprotein was detected in 13 (72.2%) of the 18 untreated TCCs of the upper urinary tract (UUT), 6 (31.6%) of the 19 untreated TCCs of the bladder, and all of the 4 TCCs treated with M-VAC chemotherapy, respectively. Fourteen (87.5%) of the 16 TCCs with a positive expression of P-glycoprotein were resistant to ADM and VBL, whereas all of the 4 TCCs sensitive to both drugs were negative in the expression of P-glycoprotein. The succinate dehydrogenase activity of TCCs with a positive expression of P-glycoprotein was significantly higher than that of TCCs with a negative expression of P-glycoprotein (P < 0.05). Thus, there was a good correlation between the expression of P-glycoprotein and MDR phenotype in the chemosensitivity test. These results suggest that intrinsic MDR exists in some TCCs of the urinary tract, particularly UUT, and that the immunohistochemical investigation of P-glycoprotein may be useful for predicting the MDR phenotype in TCCs of the urinary tract.