METALLOTHIONEIN EXPRESSION IS CORRELATED WITH CISPLATIN RESISTANCE IN TRANSITIONAL-CELL CARCINOMA OF THE URINARY-TRACT

Metallothioneins (MTs) are small cysteine-rich, metal-binding proteins involved in resistance to heavy-metal toxicity, and are known to bind cisplatin. Several experiments suggest possible involvement of MT in cellular resistance to cisplatin. To investigate the relationship between MT expression and cisplatin resistance in urinary tract transitional cell carcinoma (TCC), immunohistochemical staining for MT was performed in 31 untreated TCCs of the urinary tract. The results were compared with the sensitivity of the tumors to cisplatin as assessed by the microtiter succinate dehydrogenase inhibition (mSDI) test. Variable MT expression was observed in all 31 TCCs, but there was no specific correlation between histopathological parameters and MT expression. Fourteen (87.5%) of the 16 TCCs with less than 10% of their tumor cells positive for MT were sensitive to cisplatin. On the other hand, 6 (75.0%) of the 8 TCCs with MT expression by more than 30% of their tumor cells were resistant to cisplatin, and there was a significant correlation between MT expression and cisplatin resistance (p < 0.01). These results suggest the possible involvement of MT in the intrinsic cisplatin resistance of urinary tract TCC and that immunohistochemical investigation of MT may be useful for predicting the response of these tumors to cisplatin therapy.