Products of cells cultured from gliomas. VII. Extracellular matrix proteins of gliomas which contain glial fibrillary acidic protein

Abstract

Extracellular matrix (ECM) components of two glial fibrillary acidic protein positive (GFAP+) glioma lines U251 and UM6 were studied by silver stain, morphometry, immunofluorescence, enzyme-linked immunosorbent assay, and biosynthetic labeling. Both GFAP+ lines expressed the following qualitative features in common with previously studied GFAP-negative gliomas: (a) laminin, (b) type IV collagen, (c) extracellular fibrils of silver-reducing collagen (d) pattern of reactivity with lectins. Quantitative differences in GFAP+ glioma proteins included less collagen and more laminin than GFAP-negative gliomas. Sparse collagen of GFAP+ gliomas aggregated as extracellular masses. Individual cells of UM6 simultaneously expressed GFAP and mesenchymal ECM components. Results show qualitative similarities of ECM expression among GFAP+ and negative gliomas suggesting a common lineage of these two glioma cell types and universal expression of two epithelial components of ECM, laminin and type IV collagen, among cultured gliomas. Moreover, there is a diversity of quantity and type of ECM proteins of GFAP+ gliomas with the U251 line most restricted in its expression of ECM components and with UM6 manifesting markers of epithelial and mesenchymal lineage. This diversity suggests a capacity for regulation of phenotypic expression of ECM beyond that explained simply by the presence of two cell types of different lineage.