Metallothionein gene expression in bladder cancer exposed to cisplatin

Some 68% of bladder tumors will respond to cisplatin-based chemotherapy but only 30% will have a durable response. Recent studies have suggested that the metallothionein (MT) gene may produce cisplatin drug resistance in cell lines. To determine the role of MT gene overexpression in human tumors resistant to cisplatin, we evaluated 19 bladder tumors, seven of which had been exposed to cisplatin, for MT mRNA expression. By Northern analysis, four of the seven tumors exposed to cisplatin overexpressed the MT gene compared to untreated tumors. Of the three treated tumors without MT overexpression, one was a relapse 4 yr after the last dose of cisplatin and the other two received only one dose of chemotherapy. MT gene overexpression was found in some tumors that had failed cisplatin chemotherapy and may be a mechanism for drug resistance in bladder cancer.