p53 immunoreactivity in astrocytomas and its relationship to survival.

p53 is a putative tumour suppressor gene implicated in a wide range of human malignancies. Mutation of p53 gene results in a more stable product and increased quantities of p53 protein in the cell. Thus, unlike the normal situation, mutated p53 is detectable by immunohistochemistry. We stained frozen sections of 74 astrocytomas with two antibodies to p53, PAb 1801 and PAb 421. Overall 18/74 (24%) of astrocytomas showed p53 immunoreactivity. Fifteen of 47 (32%) grade IV were p53 immunopositive, as were 3/16 (19%) grade III, 0/7 (0%) grade II and 0/4 (0%) grade I astrocytomas. These findings are in agreement with previous studies in showing relatively greater numbers of high grade than low grade p53 immunopositive tumours. Although we found an expected difference in survival according to grade, there was no significant difference in survival (p > 0.1) between p53 immunopositive and immunonegative tumours. We conclude that, whilst p53 undoubtedly plays an important role in the molecular 'chain' leading to malignancy in some astrocytomas, within tumours of comparable grade it does not appear to influence survival.