HUMAN GLIOMA ASSOCIATED INTERMEDIATE FILAMENT PROTEINS - OVER-EXPRESSION, COLOCALIZATION AND CROSS-REACTIVITY

The identification of human brain tumor-associated markers could facil itate the development of new diagnostic and therapeutic strategies for these malignancies. The type III intermediate filament proteins (IFPs ): vimentin, desmin and glial fibrillary acidic protein (GFAP) were st udied in human glioma tissue extracts, in sera from glioma patients an d in low passage glioma cell lines prepared from primary cultures of f reshly dissected tumors. Radioimmunoassay (RIA) studies, using anti-GF AP, anti-desmin and anti-vimentin mAbs, showed high levels of these pr oteins in glioma extracts. Binding studies with authentic IFPs indicat ed the absence of circulating antibodies against these proteins in the sera of glioma patients. On the other hand, these sera showed high le vels of vimentin. Binding studies with these antibodies using RIAs and western immunoblotting, showed that while anti-GFAF mAbs were specifi c to GFAP, anti-desmin mAb cross-reacted completely with GFAP, anti-vi mentin mAb cross-reacted substantially with desmin and GFAP. Immunoflu orescence staining of frozen sections revealed high levels of neurofil aments in gliomas and strikingly low levels in normal brain tissue. Do uble immuno-fluorescence staining showed co-occurrence of all three IF Ps in the same filaments. This suggests either co-expression or cross- reactivity of these proteins due to their high degree of homology. Thu s, caution should be exercised in the use and interpretation of immuno histochemical data using antibodies to IFs.