[Identification of prognostic parameters for renal cell carcinoma by cDNA arrays and cell chips]

We report here an example of how the combined application of cDNA and tumor array can lead to the identification of a novel prognostic marker within a very short time. A cDNA array analysis was performed on 5184 cDNA clones on a filter to screen for genes with differential expression between the renal cancer cell line CRL-1933 and normal kidney tissue to identify genes with relevance in RCC. There were 89 differentially expressed genes in the cancer cell line, one of them coding for vimentin, a cytoplasmic intermediate filament. To determine the in vivo prevalence and prognostic significance of vimentin expression, a renal cancer tissue micro array containing 532 RCC specimen was constructed and vimentin expression was determined by immunohistochemistry. Vimentin expression was frequently seen in clear-cell (51%) and papillary RCC (61%), but rarely in chromophobe RCC (4%) and oncocytomas (12%). These results obtained from minute arrayed tumor samples match with previous findings on vimentin expression in renal tumors. Furthermore, vimentin expression was significantly associated with poor patient prognosis (p < 0.007) independently of grade and stage. These results suggest that tissue microarray analysis provides a rapid and powerful method to determine the prevalence and prognostic significance of novel candidate genes discovered to be involved in cancer development with large-scale cDNA expression arrays. The tissue array can be adapted as a routine tool in research laboratories for analyses of large tumor series at the DNA, RNA or protein level. With such a tool, cancer researchers can study vast numbers of tumor samples in a short time and can generate a wealth of data on the application of tumor markers.