Apoptosis detected with monoclonal antibody to single-stranded DNA is a predictor of recurrence in intracranial meningiomas

Precise quantitation of apoptotic cells in meningiomas is necessary to determine the role of apoptosis in tumor growth and recurrence. In this study, we investigated the incidence of baseline apoptosis in relation to p53 and bcl-2 protein expression, proliferation status as expressed by Ki-67, PCNA and mitotic counts, standard clinicopathological parameters and patients' outcome, in a series of 59 patients with primary intracranial benign and atypical meningiomas. Seven tumors recurred (11.9%) following complete surgical resection, within a follow-up period ranging from 21 to 108 months. Apoptotic fractions were quantified immunohistochemically by means of a novel monoclonal antibody recognizing exposed single-stranded (ss) regions in the DNA of apoptotic cells during heating. Tissues consisted of archival formalin-fixed paraffin-embedded meningioma specimens. The apoptotic index (AI) ranged from 0% to 2.90% (mean: 0.50%), increased with proliferative activity (p = 0.014), had lower values in transitional meningiomas (p = 0.001) and was unrelated to grade and p53 expression. Increased AI predominated among bcl-2 negative tumors (p = 0.041) and tended to be accompanied by a shortened recurrence-free survival, in univariate (p = 0.0407) as well as in multivariate analysis (p = 0.0405). These results implicate apoptotic rate in meningioma growth and recurrence and denote that assessment of apoptotic potential by means of anti-ssDNA monoclonal antibody provides valid prognostic information irrespective of other parameters.