Proliferation and cell death in oligodendrogliomas

The rates of cell proliferation and of cell loss influence the growth rate of a tumour and reflect genetic changes. We studied proliferation and apoptosis in oligodendrogliomas and their relationship to progression of the tumours. Thirty-two cases of oligodendroglioma were retrieved spanning a 10-year period. The diagnosis and grade were reviewed and follow-up data obtained. Mitotic index (MI) and apoptotic index (AI) were determined from haematoxylin and eosin (H & E) stained sections. A labelling index (LI) of proliferating cells was obtained using the MIB1 antibody to the Ki-67 antigen. A further index of apoptosis was obtained using in situ end-labelling of DNA strand breaks (TUNEL index, TI). Fourteen cases were graded as II, 18 as III (1993 WHO). LI was significantly higher in grade III than in grade II tumours (P < 0.01) but the difference in apoptotic indices between grades was not significant. There was a significant (P = 0.036) positive correlation between the logarithms of TI and LI. Construction of survival curves demonstrated a significance difference in survival according to histological grade (P < 0.05). Stratification of cases by LI alone did not predict significantly different survival outcomes, and apoptotic indices did not demonstrate a relationship to survival. A positive relationship was demonstrated between proliferation and apoptosis in oligodendrogliomas. The levels of apoptosis observed indicate that this phenomenon may have an important influence on the overall rate of tumour growth.