CHARACTERIZATION OF GLIAL FILAMENT CYTOSKELETAL INTERACTIONS IN HUMANASTROCYTOMAS - AN IMMUNO-ULTRASTRUCTURAL ANALYSIS

The role that glial filaments play in cells and tumors of glial origin is not well understood. We therefore undertook the present study to d etermine the relationships between glial and vimentin intermediate fil aments (IFs), actin microfilaments, and CD44, a cell surface glycoprot ein important in cell migration and invasion, in human astrocytoma cel ls. Three astrocytoma cell lines, U343 MG-A (U343), U251 MG (U251), an d antisense GFAP-transfected U251 (asU251) were studied using immunofl uorescence confocal and immunoelectron microscopy. Furthermore, we stu died the phenotypic behaviour of these astrocytoma cell lines by analy zing their migration through Matrigel in vitro. U343 astrocytoma cells had the highest expression levels of glial fibrillary acidic protein (GFAP), whereas asU251 had virtually no expression of GFAP. Parental U 251 cells had intermediate expression levels of GFAP. The elimination of GFAP expression in as U251 cells was accompanied by a marked increa se in vimentin, actin microfilaments and CD44 levels. Gold labeling de nsity counts of cytoskeletal and cell surface elements demonstrated th at the differences between GFAP, actin, CD44 and vimentin levels in th e different astrocytoma cell lines were statistically significant (p < 0.05). Results from the in vitro invasion assay revealed that U343 ce lls demonstrated the least invasive potential, whereas asU251 astrocyt oma cells demonstrated the most. Our results show that elimination of GFAP expression by antisense leads to marked alterations in cell morph ology and phenotypic behaviour. These data imply that GFAP may be link ed spatially and functionally to cytoskeletal elements which may be al tered when this IF is deleted in astrocytomas.