Bladder Cancer Diagnostics and Onset of New Strategies
The diagnosis of bladder cancer is based on the information provided by cystoscopy, the gold standard, in combination with urinary cytology findings. The development of genomic markers is still a matter of research, the assays being time-consuming, expensive and difficult to standardise. Gene profiling could already be successfully applied to classify bladder tumours based on their progression and clinical outcome. Sanchez-Carbayo et al.¹ performed gene discovery in bladder cancer progression using complementary DNA microarrays by comparing the expression profiles of early-stage and advanced bladder tumours, using cDNA microarrays containing 17,842 known genes and expressed sequence tags. As a result, cytokeratins 20, neuropilin-2, p21 and p33ING1 were selected among top-ranked molecular targets differentially expressed and validated by immunohistochemistry using tissue microarrays. Their expression patterns were significantly associated with pathological stage, tumour grade and altered retinoblastoma (RB) expression. The results of such research are a basis for development of new specific genomic and proteomic bladder cancer assays. The results and applications of genomics and proteomics can be regarded as complementary and do not exclude each other. At present, proteomics-derived biomarkers can already be applied in the daily practice of the urologist. The term ‘proteome’ has been adopted to specifically describe the unique complement of proteins that reside in a cell. A new class of markers and assays has been developed within this area and some have already been successfully clinically investigated in larger studies.

Proteomic Profiling for the Detection of Cancer – General Aspects and Techniques
Proteomics is an increasingly powerful and indispensable technology in molecular cell biology. The key, but little understood, technology in mass spectrometry (MS)-based proteomics is peptide sequencing, which has recently been described and reviewed in an easily accessible format.2 Two- dimensional (2-D) gel electrophoresis is conventionally used as a first step to separate and isolate the proteins based on size (mass) and isoelectric point (pH gradient), resulting in many protein spots. Identification of proteins present or absent from tumour tissue, compared with tissue from normal or benign disease tissues, may allow the detection of tumour-specific proteins. Gel electrophoresis techniques are suited for combination with technologies such as laser capture microdissection (LCM) and highly sensitive MS. These methods are currently being used together to identify greater numbers of lower abundance proteins that are differentially expressed between defined cell populations. Additionally, surface-enhanced laser desorption/ionisation time-of-flight (SELDI-TOF) analysis enables the high-throughput characterisation of lysates from very few tumour cells or body fluids and may be best suited for the diagnosis and monitoring of disease. SELDI is an affinity-based mass spectrometric method in which proteins of interest are selectively absorbed into a chemically modified surface on a biochip. The commercial SELDI system is based on ready-made arrays of addressable binding sites on multisample strips. These ProteinChip® arrays are available with different chemically defined surfaces that permit protein binding based on hydrophilic, ionic or hydrophobic interactions or on affinity for metal chelates, so that a range of protein classes may be identified in a relatively simple screening strategy. In SELDI-TOF-MS analysis, a nitrogen laser desorbs the protein/energy-absorbing molecule mixture from the ProteinChip array surface, enabling the detection of the proteins captured by the array. Once captured on the SELDI protein chip array, proteins are detected by TOF MS.