Investigation of intermediate filaments in astrocytomas

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The aim of this project was to evaluate the role of phosphorylation-dephosphorylation regulating assembly of intermediate filament proteins in astrocytic tumors, and to clarify the biological characteristics of gliomas. GFAP (glial fibrillary acidic protein) and vimentin are two major intermediate filament proteins of astroglia. Pertinent findings are described as below, 1) We conducted immunohistochemical studies of specimen removed from 20 patients with low-grade astrocytomas (Grade II) and 21 patients with malignant gliomas including 10 anaplastic astrocytomas (Grade III) and 11 glioblastomas. Anti-phosphorylated GFAP antibody (pG2) did not stain the tissues of astrocytoma Grade II nor Rosenthal fibers. Both were strongly GFAP-positive. 2) In 5 among 21 specimens obtained from patients with malignant gliomas including anaplastic astrocytomas and glioblastomas, pG2 positively stained the tumor cells. Two were glioblastomas and 3 anaplastic astrocytomas. While pG2 stained only mitotic cells which gained phosphorylated GFAP in experiments performed elsewhere using U251 monolayr cells, our results showed the stained cells were mainly in interphase. 3) We found no difference between patients with pG2-positive tumors and those with negative tumors in evaluating time-intervals after treatment to recurrence and survival time. 4) We obtained non-specific findings in experiments studying astrocytic tumors using anti-vimentin antibodies. Experiments using anti-phosphorylated vimentin antibodies which are newly developed in our laboratory, adding the experiments of stored frozen specimen, are in progress.