Detection of proliferative cells in colorectal carcinomas and adenomas by monoclonal antibody to DNA polymerase alpha

DNA polymerase alpha is an endogenous DNA replication enzyme expressed in all cells in a proliferation cycle. An immunoperoxidase method and the monoclonal antibody to DNA polymerase alpha were used to identify proliferating cells in colorectal carcinomas (n = 35) and adenomas (n = 43). The labeling index (L.I.) in colorectal carcinomas was 51.6%, being significantly higher than 28.6% in adenomas. The L.I. in colorectal carcinomas correlated with clinical staging (stage I: 33.1%, stage II and III: 49.5%, stage IV and V: 66.9%). Furthermore, the L.I. had a tendency to elevate as carcinoma deeply invaded (pm: 25.8%, ss-s or a1-a2: 52.2%, si or ai: 67.5%). The L.I. in adenoma was related to the degree of atypia. The L.I. in adenomas with mild atypia, with moderate atypia, and cancer in adenoma were 18.3%, 31.5%, and 47.0%, respectively. And the L.I. of cancer in adenoma had no significant difference in advanced carcinomas (47.0% vs 51.6%). These results suggest that the L.I. is useful as a marker for evaluating the degree of biological malignancy of human colorectal carcinomas and the degree of histopathological atypia of adenomas.