Metallothionein isoform gene expression in four human bladder cancer cell lines

Abstract

The expression of metallothionein (MT) has been demonstrated using immunohistochemical methods in a number of human tumors, including: testicular embryonal carcinomas, thyroid tumors, transitional cell carcinomas of the bladder, in situ and invasive breast carcinomas, malignant melanomas, pancreatic carcinomas, and salivary gland tumors. In the most widely studied instance, ductal breast carcinoma, the expression of immunoreactive MT has been shown to correlate with a poor disease prognosis [1–4]. In more limited studies, the immunohistochemical expression of MT in transitional cell carcinomas of the urinary tract has been correlated with tumor resistance to chemotherapeutic regimens employing cisplatin or cisplatin alone [5, 6]. However, the direct correlation of MT expression with a poor prognosis is not universal. In colorectal adenocarcinoma, an inverse correlation of MT expression to tumor stage and lymph node involvement was demonstrated [7]. While these studies demonstrate the potential use of MT as a prognostic indicator, interpretation is limited by the fact that the MT antibody reveals expression of a family of genes, not a specific gene product. In humans, the MTs are encoded by a family of genes located at 16g13 that contains 10 functional and 7 non-functional MT isoforms [8–11]. Based on charge characteristics, the genes are divided into four classes designated 1–4. With the exception of MT-4 which has not been extensively studied, the other MT genes have been shown to exhibit inducer-, tissue-, and developmental-specific patterns of gene regulation. Questions remain as to which MT gene products are being assessed in protocols using MT immunolocalization to define tumor prognosis and if expression patterns vary within and among tumors. As an initial step in addressing whether different MT isoforms are expressed in transitional cell carcinomas of the urinary tract, the present study uses reverse transcription-polymerase chain reaction (RT-PCR) technology as described previously to determine the expression of the human MT isoforms in four bladder cancer cell lines [12].