Comparative Gene Expression Profiling Analysis of Urothelial Carcinoma of Renal Pelvis and Bladder

Expression profiling by arrays Urothelial carcinoma (UC) can arise at any location along the urothelial tract, including the urethra, bladder, ureter or renal pelvis. Although tumors arising in these various locations demonstrate similar morphology, it is unclear whether the gene expression profiles are similar in the upper tract (ureter and renal pelvis) or in the lower tract (bladder and urethra) carcinomas, especially given their different embryologic origins. As differences may facilitate potentially different screening and treatment modalities, we sought to examine the relationship between urothelial carcinoma of the renal pelvis (rUC) and urothelial carcinoma of the bladder (bUC). Fresh tumor tissue was collected from patients with bUC (n=10) and benign mucosa from the bladder (n=7) was collected from individuals undergoing resection for non-UC conditions for comparison. Gene expression profiles from these samples were determined using high-throughput Affymetrix gene expression microarray chips. Bioinformatic approaches were used to compare gene expression profiles of these samples and those of rUC (n= 14) and normal kidney (n=14) that were mostly used in our previous publication. Using unsupervised analytic approaches, rUC and bUC were indistinguishable. When supervised analytic approach was used, a very small number of potentially differentially expressed genes was identified; these differences were most likely to be limited to a single pathway - the chloride ion binding activity pathway -which was more frequently activated in rUC than in bUC. We found that the gene expression profiles of UCs from the upper and lower tract were extremely similar, suggesting that similar pathogenic mechanisms likely function in the development of these tumors. The differential expression of genes in the identified pathway may represent a potential new avenue for detection of upper tract tumors. Tissue samples with urothelial cell carcinoma from lower tract (bladder) as well as normal references were collected and the gene expression profiles were compared with gene expression profiles of samples in our previously published data set . No technical replicates.