Immunohistochemical Demonstration of Protein Kinase C Isozymes in Human Brain Tumors

Immunohistochemical studies of the expression of protein kinase C isozymes were done in 38 human brain tumors using monoclonal antibodies to three major isozymes: Type I, Type II, and Type III. The brain tumors, with the exception of 3 medulloblastomas and 2 of 6 pituitary adenomas, showed strong immunoreactivity for the Type III isozyme. Astrocytomas, anaplastic astrocytomas, and glioblastomas also showed weak immunostaining for Type II, whereas other tumors lacked this staining. Immunoreactivity for Type I was present, although weak, in some astrocytic gliomas. There was no correlation between the presence of immunoreactivity for protein kinase C isozymes or the intensity of staining for the Type III isozyme and the pathological grade of malignancy. In normal human brain tissue, Type I is localized mainly in neuronal cells, Type II in the neuropil of the cerebral cortex and the molecular and granular layers of the cerebellum, and Type III almost exclusively in astrocytes. The presence of immunoreactivity for the Type III isozyme in varying tumor cells, including those of non-astrocytic tumors and the presence of the Type II and/or Type I isozymes in astrocytic gliomas demonstrate that the expression of protein kinase C isozymes differs between normal and transformed cells.