Tissue microarray studies in bladder cancer.

The introduction of tissue microarray (TMA) methodology 10 years ago has provided a valuable tool for high-throughput genomic and proteomic analyses. Using this method hundreds of minute tissue samples can be investigated on one microscopic glass slide. Several studies demonstrated that these small tissue areas are representative for the entire tumour block and can provide reliable information on the relation of molecular markers and clinical outcome of the patient. Types of TMA used in bladder cancer research include defined clinical case series, stage-specific series (e.g. pT1), stage progression series, TMAs containing all specimens from clinical trials for specific therapies, flat (pre)neoplastic lesions, cell culture pellets and mouse model TMAs. The TMA technique has frequently been used in bladder cancer research to evaluate immunohistochemical candidate markers for prognosis and to reveal the amplification frequency of candidate oncogenes in regions with copy number alterations detected by comparative genomic hybridization and array-based methods. In addition, multimarker expression studies of several specific biological functions (e.g. apoptosis or cell-cycle proteins) or signal transduction pathways have been performed. TMAs are also used for validation of array-based gene expression studies on the protein level. TMA technology represents a crucial technique for translating new information on molecular changes in bladder cancer into clinical practice.