Tumor cell proliferation and apoptosis associated with the Gamma Knife effect

In this study, the expression of proliferating-cell nuclear antigen (PCNA) and Bcl-2 protein was examined in neurinomas, meningiomas, pituitary adenomas, and malignant lymphomas before treatment with Gamma Knife radiosurgery. Tumor volume was rapidly reduced by radiosurgery in all malignant lymphomas and in some benign tumors. The latter had been characterized by strong positive immunohistochemical staining for PCNA and Bcl-2. Radiation-induced apoptosis is thought to contribute to the low-dose effects of Gamma Knife radiosurgery. A population with a large proportion of proliferating cells may be susceptible to the induction of apoptosis, and the presence of Bcl-2 may not suppress this Gamma Knife effect.