Apoptosis in cerebral astrocytic tumours and its relationship to expression of the bcl-2 and p53 proteins.
Apoptosis is an important determinant of tumour growth which can be regulated by the bcl-2 and p53 genes. This study examines the relationship between apoptosis, growth fraction (Ki-67 immunolabelling index), and accumulation of the bcl-2 and p53 proteins in a spectrum of cerebral astrocytic tumours (n = 81), including fibrillary astrocytomas (n = 16), anaplastic astrocytomas (n = 19), and glioblastomas (n = 46). Median apoptosis indices (AIs) increased across this spectrum of tumours, and a significant (P < 0.0001) correlation was demonstrated between AI and Ki-67 labelling index (LI). Immunolabelling with the bcl-2 antibody was found in 44% of fibrillary astrocytomas, 42% of anaplastic astrocytomas, and 28% of glioblastomas. It was also found in the vascular endothelial proliferation typically seen in glioblastomas, and in the giant, multinucleated cells of some glioblastomas. No clear relationship between AI and bcl-2 accumulation was evident. Immunolabelling with the p53 antibody was found in 56% of fibrillary astrocytomas, 79% of anaplastic astrocytomas, and 50% of glioblastomas. No clear relationship between AI and patterns of p53 immunolabelling was evident. Equal proportions of p53-positive tumours were bcl-2 positive and bcl-2 negative, but a small proportion of p53-negative tumours was bcl-2 positive. The correlation between AI and Ki-67 LI is in line with findings in other malignant tumours. We suggest that the regulation of apoptosis in astrocytic tumours is too complex for a clear association between AI and bcl-2 and p53 protein expression to be demonstrated.
D000911:Antibodies, Monoclonal; D017209:Apoptosis / Q000502:physiology*; D001254:Astrocytoma / Q000378:metabolism / Q000473:pathology*; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology*; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D016158:Genes, p53 / Q000235:genetics; D005909:Glioblastoma / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2
D000911:Antibodies, Monoclonal; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2