Immunohistochemical study of glial fibrillary acidic protein in avian sarcoma virus-induced gliomas in dogs.

Anaplastic astrocytomas, gliosarcomas and sarcomas were induced in 33 neonatal dogs by intracerebral injection of purified Schmidt-Ruppin strain of avian sarcoma virus (ASV). A total of 11 anaplastic gliomas, 7 gliosarcomas and 18 sarcomas were induced. Ten of the 11 anaplastic astrocytomas and all 7 gliosarcomas were positive for GFAP using the peroxidase-antiperoxidase method on formalin-fixed, paraffin embedded tissue. None of the sarcomas were positive for GFAP. One anaplastic astrocytoma was analyzed by gel electrophoresis and immunoblot and the amount of GFAP in the tumor was compared with comparable samples from normal white and gray matter. Densitometric analysis of the GFAP stained gels showed that 12-13% of tumor protein was GFAP compared with 2-3% for the non-neoplastic white and gray matter. The results of this study add further evidence to the astrocytic origin of many of the induced anaplastic primary brain tumors by ASV.