Expression of vimentin, glial filament, and neurofilament proteins in primitive childhood brain tumors. A comparative immunoblot and immunoperoxidase study.

Two methods of determining intermediate filament protein (IFP) expression by primitive brain tumors of childhood were compared using a panel of monoclonal antibodies to three classes of IFP. In addition to a controlled immunohistochemical study, a group of these tumors was subjected to direct immunologic assay of tumor-extracted IFP using the western blot method. Western blots of IFP extracted from ten prospectively microdissected brain tumors revealed no NF200 or NF150 in any tumor. Traces of NF68, VFP, and GFP were detected by this sensitive method in four, three, and six cases, respectively. Immunohistochemistry, using the same monoclonal antibodies on adjacent tumor sections, yielded results significantly different from the immunoblotting method: no NF proteins or VFP were detected, but immunoreactive GFP could be seen in a small percentage of cells in each case. A retrospective study of 46 primitive tumors, using only immunohistochemistry, showed GFP to be the most common source of immunopositivity (38 cases), followed by VFP (15 cases), but most positive cells were judged to be reactive astrocytes. NF protein was not detected except in three cases in which extremely rare cells had morphological features of neurons. Cells which were clearly malignant, and which constituted the majority of cells in a microscopic field, were devoid of any IFP immunoreactivity. The advantages and limitations of each method of IFP detection in this group of primitive tumors and the implications of the apparent paucity of mature neural IFP in these tumors are discussed.