Expression of non-glial intermediate filament proteins in gliomas

Non-glial intermediate filament (IMF) proteins, as well as glial fibrillary acidic protein (GFAP) and vimentin, were studied by immunohistochemistry in 24 gliomas including low grade astrocytoma, pleomorphic xanthoastrocytoma, anaplastic astrocytoma, glioblastoma, oligodendroglioma, ependymoma and ependymoblastoma, which were fixed in ethanol and embedded in paraffin. Cytoskeletal elements isolated from two glioblastomas were examined with immunoblot analysis. All tumors had GFAP-positive neoplastic cells and vimentin was also found in all the tumors except one oligodendroglioma. Twenty-three gliomas were immunostained with anti-desmin polyclonal antibody (DM-P), but anti-desmin monoclonal antibody reacted to only one glioblastoma. DM-P might crossreact with GFAP and vimentin. Cytokeratin expression was investigated with six antibodies. Twenty gliomas (83%) were positive for the antibody against epidermal keratin (CK-SE), however positive immunoreactivity varied from 58 to 8% with other cytokeratin antibodies. With the Western blot method, CK-SE had protein bands at 53 and 60-66 kDa. Neurofilament was expressed in one pleomorphic xanthoastrocytoma, one anaplastic astrocytoma, one glioblastoma and one ependymoblastoma. Expression of nonglial IMF proteins were observed in 21 tumors (88%), and coexpression of 4 or 5 classes of IMF proteins in 3 tumors (13%). We conclude that, in addition to GFAP and vimentin, gliomas express several types of non-glial IMF proteins.