Co-expression of GFAP, vimentin and cytokeratins in GL-15 glioblastoma cell line

Glial fibrillary acidic protein (GFAP), vimentin (Vi) and cytokeratin (CK) intermediate filament (IF) proteins were studied in glioblastoma cell line GL-15. The immunofluorescence staining revealed strong positive staining fo r vimentin in all cultured cells. Approximately 20% of analyzed cells showe d strong and 50% moderate intensity of staining for GFAP. About 3% of all c ells were positively stained with a mixture of anti-CK monoclonal antibodie s. The expression of all IF was not in relation to the cell density or days in vitro after passage. The double immunofluoresce revealed that all CK-po sitive cells express GFAP and vimentin. This study demonstrates the heterog eneity of the clonal GL-15 glioma cell line which consists in three immunoc ytochemically distinct cell types: Vi+/GFAP-/CK-, Vi+/GFAP+/CK-, and Vi+/GF AP+/CK+. These findings give further evidence about the expression of non-g lial IF in cultured glioma cells.