Growth fraction of human bladder tumors.

The growth fraction of bladder tumors was immunohistochemically assessed in situ using anti-DNA polymerase (Pol alpha) monoclonal antibody. This enzyme is known to be present in the nucleus of the cells in G1, S, and G2 phases. The percentage of labeled cells was expressed as the labeling index (LI). The average LI was 6.0% in normal epithelium and 17.8% in bladder tumors, this difference being significant. The labeled cells were distributed throughout both the basal and surface layers of bladder tumors. However, in some bladder tumors, the distribution of Pol alpha-labeled cells varied from area to area. The higher fraction of labeled cells was found in high grade or invasive tumors. Papillary and nodular bladder tumors showed a greater rate of cell proliferation than papillary tumors. These findings suggest that Pol alpha immunostaining could be a potent tool for easy and quick evaluation of proliferating cells in bladder tumors, thereby providing a supplement to conventional histological findings.