Identification of true differentially expressed mRNAs in a pair of human bladder transitional cell carcinomas using an improved differential display procedure.

Differential display in combination with arbitrarily primed polymerase chain reaction (PCR) fingerprinting has become one of the most powerful techniques to identify and isolate mRNAs that are differentially expressed in pairs of biological samples. However, in many cases the cDNA band corresponding to the differentially amplified product contains several cDNA species that comigrate with the cDNA of interest due to the poor resolution of the fingerprinting gels, thus hampering further analysis and identification of the desirable cDNA. To improve the electrophoretic resolution of differentially amplified cDNAs, we have utilized Resolver Gold agarose gel electrophoresis (Ingenius) as an additional step to overcome downstream problems encountered during RNA fingerprinting experiments. To illustrate the power of the modified differential display procedure we present a detailed analysis of the cDNA products differentially displayed in tumor biopsies obtained from a noninvasive (grade II, Ta) and an invasive (grade III, T2-T4) human bladder transitional cell carcinoma (TCC). Several genes that were differentially expressed in this tumor pair were identified. These included: tropomyosin 4, the protein disulfide isomerase precursor (PDI), MRP14, signal transducer CD24, keratins 8 and 13, cytochrome oxidase subunit IV (COXIV), putative transcription factor HOX-1.3, as well as two novel genes of yet unknown function. All of the identified cDNAs were shown to be truly differentially expressed by Northern blotting, reverse transcriptase-PCR (RT-PCR), and two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) analysis of the corresponding lesions.