p53 protein and epidermal growth factor receptor expression in human astrocytomas

Abstract

p53 mutations are the most frequently detected genetic alterations of gliomas, appearing in a similar proportion of low and high grade astrocytomas, while the amplification of epidermal growth factor receptor (EGFR) gene appears mainly in glioblastomas. Thus, these changes seem to delineate two subgroups of high grade astrocytomas: those originating from preexistent low grade astrocytomas and those originating de novo. Paraffin-embedded surgical specimens from 56 human astrocytomas (8 pilocytic (I.) astrocytomas, 9 low grade (II.) fibrillary astrocytomas, 9 high grade (III.) anaplastic astrocytomas and 30 glioblastomas) were analyzed immunohistochemically for the presence of p53 protein and EGFR. Approximately 41% of all cases were p53-protein-positive while 23% were EGFR-positive. Five cases (8.9%) were double-positive for p53 protein and EGFR. The p53-immunopositive nuclei were revealed in 16 cases (53.3%) of glioblastomas, 3 cases (33.3%) of high grade and 4 cases (44.4%) of low grade astrocytomas. None of pilocytic tumors was p53-positive. EGFR immunopositivity increased with the grade of malignancy (11.1%, 22.2% and 33.3%). Double EGFR-p53-positive cases occuried in similar proportions in all grades (approximately 10%) and did not show different survival rate. There were no differences between average age of patients with only-p53-positive, p53-negative (pilocytic tumors excluded) and only-EGFR-positive tumors.