Correlation of DNA ploidy levels with altered cytokeratin patterns in rat bladder tumors

Flow cytometry analysis of primary bladder carcinoma cells is appropriate for demonstrating the association between the presence of aneuploid cells and increased malignant potential for transitional cell carcinoma (TCC). Our laboratory previously has reported a specific alteration in the cytokeratin (CK) pattern of experimentally induced bladder carcinomas in rats. Unique immunohistochemically detectable changes in CK expression were the loss of CK 13 expression in invasive TCC cells and the loss of CK 19 expression in induced TCC. We now report the correlation of these changes in CK expression with cellular aneuploidy of the induced bladder carcinomas. Bladder carcinomas were induced in rats by direct instillation of N-methyl-N-nitrosourea. Immunohistochemistry was performed on the induced tumors using four commercially available monoclonal antibodies specific for CK 18 (TR1031), CK 13 (K8.12), CK 19 (K4.62), and the CKs 5, 7, and 8 (K8.13). Flow cytometry data from the induced bladder carcinomas was analyzed and the DNA index, proliferative index, and percent aneuploid cells were calculated for each time point. The percent aneuploid cells and CK 19 staining were tested statistically and were shown to be negatively correlated. We therefore hypothesize that the combination of the loss of CK 19 as detected by the antibody K4.62 coupled with the presence of aneuploid cells in histopathologically diagnosed invasive TCC is a significant factor in predicting the prognosis for any given diagnosis.