Overexpression of p27kip1 in urinary bladder urothelial carcinoma

Objectives: Cyclins and cyclin-dependent kinase (CDK) complexes have important regulatory roles during cell cycle progression and can be used as prognostic markers in various kinds of malignant tumors. This study investigated the expression of proliferative cell nuclear antigen (PCNA), p53, Rb, p27(kip1), and cyclin D1 by immunostains in bladder tumors, especially urothelial papilloma, papillary urothelial neoplasm of low malignant potential, and low and high grade urothelial carcinoma, to see if their expression is associated with classification or grading of the urinary bladder urothelial carcinoma. Method: Nuclear expression of PCNA, p53, Rb, p27(kip1), and cyclin D1 was determined immunohistochemically in a series of 89 urinary bladder tumor specimens, including 13 papilloma, 15 urothelial neoplasm of low malignant potential, 17 low grade urothelial carcinoma, and 44 high grade urothelial carcinoma. The results of immunoreactivity were analyzed with respect to the associations with tumor grade. Results: Eighty- two percent (38/45) of the p27(kip1) positive tumors were urothelial carcinoma, and the percentage of the p27(kip1) positivity was higher with increasing grade of the urothelial carcinoma ( P = 0.011). A tendency of higher percentage of positive p53 immunoreactivity was noted in the urothelial carcinoma ( P = 0.053). There was no significant difference in cyclinD1, Rb and PCNA expression between benign, low malignant potential and urothelial carcinoma. Conclusion: We first noted an overexpression of p27(kip1) in urinary bladder urothelial carcinoma. The result indicates that some urothelial carcinomas may tolerate this inhibitor of cell cycle progression.