To date, molecular evidence studies for bladder cancer, using the microarray technology, are focusing on the transitional cell carcinoma, however, similar fingerprinting studies have rarely been performed on the other molecular phenotypes of bladder cancer, squamous cell carcinoma (SCC). This study was conducted to monitor the gene expression profiles for bilharzial-related SCC of the bladder to be able to compare its data with transitional cell carcinoma microarray data. A total of 17 paired bilharzial urinary bladder SCC specimens and their corresponding normal urothelium were analyzed using the complementary deoxyribonucleic acid microarray hybridization approach to study the molecular basis of the development of SCC of the urinary bladder. Validation of the microarray results was performed using the Northern blotting technique. After supervised analysis of the microarray data, there was at least a 3-fold difference in the expression between SCC of the bladder and normal urothelium in 82 genes. A total of 38 genes were up-regulated in SCC of the bladder, including matrix degradation-related genes, growth factors, different oncogenes, and immunology related genes. Conversely, 44 genes were down-regulated in SCC of the bladder, including integrins, laminins, cadherins, nonmetastatic cell 1 (NM23) and apoptosis-related genes. Our findings can explain the aggressive behavior of SCC of the bladder. Such gene profiling studies will add to our understanding of the mechanisms of carcinogenesis, and may also improve our ability to diagnose and treat bladder cancer. (c) 2007 Elsevier Inc. All rights reserved.