Immunohistochemical Assessments of P53 Protein Accumulation and Tumor Growth Fraction During the Progression of Astrocytomas

P53 protein accumulation and growth fraction were assessed immunohistochemically in primary and recurrent astrocytoma with malignant progression. The tumors analyzed were diffusely infiltrating astrocytomas of the cerebral hemispheres and they were graded according to the World Health Organization (WHO) criteria into low grade astrocytoma (grade II), anaplastic astrocytoma (grade III), and glioblastoma (grade IV). The fraction of P53-positive cases, i.e., biopsies containing P53 immunoreactive cells, significantly increased during progression, in group II–III from 65% to 90%, in group II→IV from 68% to 95%, and in group III→IV from 69% to 100%. None of the initially P53-positive cases became P53 negative after progression. During progression, the P53 labeling index (LI)increased significantly in groups II→III (3.5%→9.8%) and II→ IV (3.3%→13%), suggesting that P53 immunoreactive glioma cells may have a growth advantage. The mean proliferating cell index (PI), analyzed by monoclonal antibody MIB-1, increased significantly in groups II→III (2.5%→11%), II→IV (2.9%→19%), and III→IV (8.7%→16%). Gemistocytes showed a significantly lower PI than the average of all tumor cells.