Expression of cytokeratin 20 in urinary cytology of patients with bladder carcinoma

BACKGROUND Of the 20 known cytokeratins, CK‐19 is expressed in normal urothelium, whereas the recently identified CK‐20 is expressed in urothelial carcinoma cells but not in normal urothelial cells. The aim of this study was to examine whether CK‐20 expression could serve as a noninvasive test in which malignant urothelial cells in urine are detected and monitored. METHODS In the current study, the authors used reverse transcriptase‐polymerase chain reaction (RT‐PCR) methods to determine the expression of CK‐20 in cells separated from the urine of patients with bladder carcinoma. Cells were obtained from the urine of 87 patients divided into the following 2 groups: 1) 14 healthy volunteers without any known history of transitional cell carcinoma (TCC), and 2) 73 patients with hematuria suspected for TCC of the bladder. For control purposes, CK‐20 expression was examined in cells of 1) bladder carcinoma tumors of 5 patients, 2) blood of either patients with bladder carcinoma (n = 5) or healthy controls (n = 5), and 3) three different cell lines. RNA of the various cell pellets was extracted and RT‐PCR was performed with CK‐20 and CK‐19 primers (CK‐19 was used as a marker for normal epithelial cells). RESULTS CK‐20 amplification band (370 bp) was obtained with mRNA extracted from TCC cells of either bladder tumor or HT‐29 line (a CK‐20 colon carcinoma line). Sensitivity of the method was found to be 91%, whereas specificity was 67%. Among the 7 false‐positive cases, 3 showed atypia, 3 hyperplasia, and 1 metaplasia, and 2 underwent previously successful TCC tumor removals, suggesting that the CK‐20 test also responded to premalignant lesions. No false‐positive cases were found in the healthy control group. No other preparation, including blood of the patients of with TCC, showed the CK‐20 amplification band. CONCLUSIONS These results indicate that CK‐20 is a potential biomarker for noninvasive detection of bladder carcinoma by assaying uroepithelial cells from the voided urine specimen with RT‐PCR. Cancer 1998;82:320‐330. © 1998 American Cancer Society. Detection of CK‐20 gene expression by reverse transcriptase‐polymerase chain reaction in urinary cytology can serve as a noninvasive method for detecting bladder carcinoma.