Role of apoptosis in the prognosis of oligodendrogliomas

Prognostic factors in oligodendrogliomas are not well defined, even considering the labeling index of proliferation markers. As in other neuroepithelial tumors, the difficulty in calculating cell loss may contribute to this uncertainty. Proliferation markers Ki-67/MIB.1 and PCNA, mitoses, apoptotic nuclei, p53 and bcl-2 expression were investigated in 98 oligodendrogliomas. Apoptosis was assessed by the aspect of nuclei, by in situ end-labeling (ISEL) technique and by c-Jun immunohistochemical demonstration. The Bcl-2 also was immunohistochemically studied for its anti-apoptotic role. Mitotic index (MI), labeling index (LI) for MIB.1 and PCNA and apoptotic index (AI) were calculated and compared among themselves and with histology and survival. It was found that AI correlated with MI (p = 0.001) and was significantly higher in anaplastic than in classic oligodendrogliomas (p = 0.001). Apoptosis occurred only slightly more frequently in cases with high LIs for proliferation markers (MIB.1 and PCNA) (p = non-significant) and it was definitely higher in p53-positive cases (p = 0.008). It did not correlate with bcl-2 which was poorly expressed in oligodendrogliomas, with the exception of cells with astrocytic features. Apoptotic index correlated very weakly with survival (p = 0.05); therefore, it cannot be considered a highly reliable prognostic factor in oligodendrogliomas.