GLIAL FIBRILLARY ACIDIC PROTEIN EXPRESSION IN A NEW HUMAN GLIOMA CELL-LINE IN CULTURE BEFORE AND AFTER XENOGENIC TRANSPLANTATION INTO NUDE-MICE

A human glioma cell line, SA146, was initiated on precoated extracellu lar matrix from a stereotactic biopsy of a glioblastoma. We report mod ulation in the expression of glial fibrillary acidic protein (GFAP) by SA146 passed in vitro before or after xenogenic transplantation into nude mice. Immunofluorescence data show a decrease in the percentage o f GFAP-expressing cells with increasing in vitro passages but a full r eexpression (100% of GFAP-positive cells among vimentin-positive cells ) was observed in cultures just derived from the xenotransplanted tumo r. These changes are correlated with the mRNA content (Northern blot p robed with a cDNA for GFAP) and with the protein level (cytoskeletal f raction analyzed by two-dimensional gel electrophoresis and Western bl ots probed with a monoclonal antibody). At the optimal level of GFAP e xpression, a large range of microheterogeneity in GFAP isoforms is rea ched for which posttranslational events are clearly involved since mRN A translation in cell free system would provide at best three isomers. We suggest that SA146 would be an appropriate model to study the regu lation of GFAP expression in the context of human glial tumor biology.