The expression of cell cycle regulatory proteins in oligodendroglial tumors

Oligodendroglial tumors are mainly classified histologically into 2 types of tumors--oligodendrogliomas and oligoastrocytomas--whether the tumor includes astrocytic component or not, and these are, respectively, divided histologically into 2 different malignant groups, low-grade (WHO grade II) and high-grade or anaplastic (WHO grade III). In this study, we investigated the expression of the cell cycle-related proteins and analyzed the relationship between the labeling index (LI: the percentage of positive nuclei) of these proteins and 2 histopathological phenotypes, grade and prognosis. Forty-four specimens were examined, including 11 oligodendorogliomas (0), 5 oligoastrocytomas (OA), 18 anaplastic oligodendrogliomas (aO) and 10 anaplastic oligoastrocytomas (aOA), according to the WHO classification. Of these, 19 specimens were obtained from recurrent tumors of 8 cases. The mean LI of all the investigated proteins between O and OA, and aO and aOA showed no significant differences. The mean MIB-1 LI, pRb LI, p53 LI and p14 LI of GIII were significantly higher than GII, while the mean p27 LI of GIII was significantly lower than GII. In the recurrent cases, we noted correlations between the disease-free period and MIB-1 LI (inverse), p27 LI and p14 (inverse). Significant correlations were noted between MIB-1 LI and pRb LI, MIB-1 LI and cycD1 LI, MIB-1 LI and p27 LI (inverse), pRb LI and cycD1 LI, cycD1 LI and cdk4 LI and pRb LI and p27 LI (inverse) in the pRb/cycD1-cdk4/p27 pathway, and between MIB-1 LI and p53 LI, MIB-1 LI and p14 LI, p53 LI and p14 LI, p53 LI and MDM2 LI and MDM2 LI and p14 LI in the p53/MDM2/p14 pathway. In conclusion, both pRb/cycD1-cdk4/p27 and p53/N4DM2/p14 pathways correlate with malignant progression, and MIB-1 LI, pRb LI, p27 LI, p53 LI and p14 LI reflect the histopathological malignancy of oligodendroglial tumors. MIB-1 LI, pRb LI and p27 LI are especially useful as indicators of malignancy of oligodendroglial tumors.