[P53 protein expression and proliferative potential in non-recurrent and recurrent meningiomas]

Evaluation of the p53 gene protein expression and proliferative potential with MIB-1 monoclonal antibody (MBL Co.), a new marker of cellular proliferation that binds Ki67 in paraffin sections, by immunohistochemical studies were made in 10 cases of the non-recurrent meningiomas and the 8 cases (17 samples) of the recurrent meningiomas. Tissue samples were embedded in paraffin after fixation in 10% formalin, and 3-microns sections were activated by microwave heating before being immersed with p53 protein or MIB-1 monoclonal antibody. The positivity of immunostaining for p53 protein and MIB-1 was calculated as the % values of tumor cell nuclei stained to all tumor cell nuclei examined within several fields under a light microscope. The mean % value of the proliferating cell index (PCI) stained with MIB-1 monoclonal antibody was 2.1% in the non-recurrent meningiomas, and high values of 11.9% were obtained for the recurrent meningiomas. High values of PCI exceeding 3% were indicated in most of the cases of recurrent meningiomas. p53 protein was not found in the 10 cases of non-recurrent meningiomas. However, it was positive showing values of 0.5-8.5% (mean; 3.4%) in 5 of the 8 cases of recurrent meningiomas. 2 of 4 cases of recurrent meningiomas with a benign type of histology at both initial discovery and recurrence revealed p53 protein expression in the tumor tissues. 3 of 4 cases of recurrent meningiomas, which were of the benign type at the initial operation but transformed to the malignant (atypical) type on recurrence, demonstrated positive staining for p53 protein in the tumor tissues. Although positivity for p53 protein was observed in the recurrent meningiomas with high values of PCI with MIB-1, no significant correlation between the values of PCI with MIB-1 and those for the p53 protein expression was found. The p53 gene protein may be altered on tumor recurrence and/or malignant transformation in meningiomas. It is concluded that evaluations of the p53 protein expression and proliferative potential with MIB-1 are important as additional factors for the prediction of tumor recurrence in meningiomas.