A comparative study of apoptosis and proliferation in germinoma and glioblastoma

Intracranial germinoma has a relatively good prognosis when treated with radiotherapy and chemotherapy, whereas glioblastoma has a poor prognosis irrespective of these treatments. Cell proliferation and cell death are opposing processes in tumor growth, with tumor progression reflecting the balance between proliferating and apoptotic cells. We investigated cell proliferation and cell death using MIB-1 staining and nick-end labeling in 13 germinomas in comparison with 11 glioblastomas. Expression of BAX and Bcl-2, which regulate apoptosis, were studied by immunohistochemistry. Although germinomas showed strong MIB-1 immunostaining similar to that seen in glioblastomas, germinomas included significantly more apoptotic cells. The ratio of apoptotic ratio to MIB-1 labeling index for germinomas was 72.9 +/- 36.9 (mean +/- SD), a higher, statistically significant ratio as compared with glioblastomas (14.5 +/- 11.2; P < 0.01). Furthermore, germinomas showed greater expression of BAX than did glioblastomas, while the expression of Bcl-2 was weak in both tumor types. A comparison of these apoptotic-related proteins showed that immunoreactivity for BAX was relatively higher in germinomas than in glioblastomas (P < 0.01), corresponding well to numerous apoptotic cells identified in germinoma tissues. These findings may account for the prognostic difference between germinoma and glioblastoma in the face of a similar proliferation potential according to MIB-1 immunostaining. The balance between cell proliferation and death should be considered when predicting outcomes in patients with intracranial tumors.