The identification of human
brain tumor-associated markers could facilitate 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 studied in human
glioma tissue extracts, in sera from
glioma patients and in low passage
glioma cell lines prepared from primary cultures of freshly dissected
tumors. Radioimmunoassay (RIA) studies, using anti-GFAP, anti-
desmin and anti-
vimentin mAbs, showed high levels of these
proteins in
glioma extracts. Binding studies with authentic IFPs indicated the absence of circulating
antibodies against these
proteins in the sera of
glioma patients. On the other hand, these sera showed high levels of
vimentin. Binding studies with these
antibodies using RIAs and western immunoblotting, showed that while anti-GFAF mAbs were specific to GFAP, anti-
desmin mAb cross-reacted completely with GFAP, anti-
vimentin mAb cross-reacted substantially with
desmin and GFAP. Immunofluorescence staining of frozen sections revealed high levels of neurofilaments in
gliomas and strikingly low levels in normal brain tissue. Double immunofluorescence staining showed co-occurrence of all three IFPs in the same filaments. This suggests either co-expression or cross-reactivity of these
proteins due to their high degree of homology. Thus, caution should be exercised in the use and interpretation of immunohistochemical data using
antibodies to IFs.