Correlation between MIB-1 staining index and the immunoreactivity of p53 protein in recurrent and non-recurrent meningiomas.

Wild type p53 protein has been shown by recent investigations to be involved in the negative regulation of cell proliferation, whereas aberrant p53 protein has lost this negative regulation of cell growth. Wild type p53 protein, which has a very short half-life, has generally been considered to be undetectable using immunohistochemical methods; however, according to a recent report, wild type p53 protein may accumulate in the nuclei because of a defective ubiquitin pathway. Aberrant p53 protein has a longer half-life, and thus is visible using immunohistochemical methods. In this study, both the proliferative potential represented by the MIB-1 staining index (SI) and the immunoreactivity of p53 protein in 51 intracranial meningiomas were studied applying immunohistochemical staining methods to archival paraffin sections. The correlation among MIB-1 SI, p53 immunoreactivity, histopathologic findings and the clinical course of the meningiomas was also analyzed retrospectively. Although it is not possible with available reagents to distinguish between aberrant p53 protein and wild type p53 protein, statistical analyses show that p53 protein was immunostained both in meningiomas with high MIB-1 SI and in recurrent meningiomas. This demonstrates the close relationship among p53 immunoreactivity, MIB-1 SI, and recurrence; therefore, the presence of p53 protein by immunohistochemical examination may suggest the proliferative activity of meningioma and is capable of serving as a predictor of future recurrence.