Molecular cytogenetic analysis of bladder cancer by array-based comparative genomic hybridization and FISH

B18

Introduction: Genetic alterations are frequently found in bladder cancer. Here we investigate the DNA copy number alterations in Taiwanese bladder cancer subpopulation using a high resolution array-based comparative genomic hybridization (CGH) technique. We also tested the diagnostic value of fluorescence in situ hybridization (FISH) in these patients using UroVysion kit.
 Materials and Methods: Whole-genome analyses were performed in fifteen bladder tumors using NimbleGen microarray system. The main feature of the microarray contains 385,000 probes on a single glass slide, which tiled through genic and intergenic regions at a median probe spacing of 6,000 bp. We also examined the polyploidy of chromosome 3, 7, 17 and aneuploidy of chromosome 21 in voided or instrumental urine from these patients.
 Results: We have identified several recurrent genetic changes in these bladder tumors. The most frequent changes of DNA alterations were deletion of chromosome 1q (70%), 8p (50%), 9q21 (50%), and 10q21.1-23.3 (50%). Other frequent gain were of chromosome 18q11.2-22.3 (50%) and 3. Several of these alterations were found in previous results from conventional CGH and loss of heterozygosity analyses on bladder tumors. However, the FISH detection rate for bladder tumor using UroVysion was 84%.
 Conclusion: Array-CGH revealed several DNA copy number alterations that were unique in bladder cancer. These alterations will help us to identify oncogenes or tumor suppressor genes that are important in the pathophysiology of bladder cancer. UroVysion, an non-invasive cytogenetic analysis tool, is a valuable method in the diagnosis of Taiwanese patient with bladder cancer.