Identification of differentially expressed genes in normal and malignant prostate by electronic profiling of expressed sequence tags

Differentially expressed genes between corresponding normal and cancer tissue can advance our understanding of the molecular basis of malignancy and potentially serve as biomarkers or prognostic markers of malignancy. To identify differentially expressed genes in prostate cancer, we used a procedure combining electronic expression profiling of the prostate expressed sequence tag (EST) database and molecular biology techniques. A novel electronic expression-profiling algorithm was developed to search publicly available EST sequences for genes that show significant differential expression in prostate cancer compared with normal prostate tissue. Approximately 600 genes expressed in prostate were identified through adequate EST counts of ESTs for electronic profiling. Of these 600 genes, 9 showed statistically significant differences in their EST counts between cancer and normal prostate and were further analyzed. The predictions associated with electronic profiling were experimentally verified for two genes, cysteine-rich secretory protein 3 (CRISP-3) and deadenylating nuclease (DAN), using real-time reverse transcription-PCR with total RNA extracted from cells isolated by laser capture microdissection. In five of five Gleason score 6 cancer cases, CRISP-3 expression was increased >50 fold, whereas the expression of RAN was reduced by >80%.