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.