HISTOPATHOLOGICAL STUDY OF METALLOTHIONEIN IN BLADDER CANCER AND RENAL CELL CARCINOMA

Metallothionein (MT) is a low molecularmetal binding protein with multiple biological functions. Recently, MT has been implicated as a factor involved in resistance to anticancer drugs, which presumably inactivates anticancer drugs, including cisplatin, and doxorubicin. In this report, we investigated the relationship of MT expression with the clinical features in bladder cancer and renal cell carcinoma. In 35 cases of bladder cancer, 10 cases of renal cell carcinoma and 3 cases of normal mucosa of bladder, the expression of MT was immunohistologically examined by avidinebiotin-peroxidase (ABC) staining of paraffin-embedded tissue specimens with anti-MT antibody. Intense MT expression was noted in all cases of normal mucosa of bladder. MT was detected in 10 of 35 cases of bladder cancer, with the incidence of MT expression being significantly higher increases with lower pathological tumor grade. MT was detected in 8 of 10 cases of renal cell carcinoma, and all of the their normal renal tubules showed more intense staining. A number of hypotheses can be proposed from these observations. First, our observation of decreased MT expression in poorly differentiated carcinomas, which are the more proliferating tumors, this suggests correlation of MT expression with proliferative status of cancer. Second, the higher incidence of MT expression in renal cell carcinoma than in bladder cancer may suggest that it is a factorresponsible for the lower efficacy of chemo-therapy in renal cell carcinoma than in bladder cancer.