Bladder cancer is one of the few malignancies in which occupational and environmental exposures to chemicals have been documented as major risk factors. The metallothioneins (MTs) are a family of low molecular weight proteins that are widely recognized as a major weapon in the cell's armamentarium for protection against and recovery from physical and chemical insult, environmental or otherwise. Thus, it is only logical that MT might have a role in human bladder cancer. In recent studies, the applicant has shown that the third isoform of MT (MT-3) is overexpressed in all human bladder cancers and in most precursor lesions. Similarly, the MT-I and MT-2 proteins have been shown to be overexpressed in some of these bladder cancers and overexpression of the protein correlates to overexpression of the MT-1X gene. The applicant hypothesizes that the early overexpression of MT-3 (and possibly other MT isoforms) sequesters Zn+2 from important regulatory molecules, including p53, through the generation of apoMT and that this in turn renders the early bladder cancer cell as a slow growing, chemotherapeutic resistant, genetically unstable cell destined to progress. The long-term goal of this application is to elucidate the mechanism/s underlying the alterations of MT gene regulation that occur in the development and progression of human bladder cancer.
Four specific aims are proposed. The first is to demonstrate that the up-regulation of MT gene expression occurs during bladder cancer progression using a cell culture based model system.
The second aim i s to show that MT-3 overexpression alters cell growth, drug resistance and genetic stability of bladder urothelial cells consistent with a role in tumor progression and to define the mechanism underlying these alterations. The third specific aim is to correlate MT gene expression to patient outcome by a retrospective analysis of paraffin-embedded tissue (PET) from patients with bladder cancer. A major goal being to identify premalignant and established lesions that are likely to progress and follow an aggressive clinical course. The final specific aim is to demonstrate that the presence of MT-3 positive urothelial cells in the urine can predict bladder cancer reoccurrence and adverse workplace exposure. The completion of these studies would provide a strong link between a protein family known to mediate the cell's response to environmental exposure and a cancer strongly associated with exposure to environmental agents.
