MOLECULAR CHARACTERIZATION OF GLIOBLASTOMA CELL-DIFFERENTIATION

OBJECTIVE: Induction of cellular differentiation continues to be an at tractive therapeutic strategy for malignant glioma. The purpose of thi s study was to develop a convenient in vitro model system for glioblas toma differentiation and to then characterize it using conventional te chniques and flow cytometry. METHODS: A subline of U138 MG cells (''U1 38B'') was treated with 0 to 4 mmol/L sodium butyrate (or serum depriv ation) for up to 96 hours. Cells were initially studied for effects on proliferation, morphology, and glial fibrillary acidic protein (GFAP) staining. Northern blot and immunoblot analyses of c-myc expression w ere performed. Multiparameter flow cytometry was then used to analyze GFAP, c-myc protein, and total cellular protein fluorescence and to re late them to changes in cell cycle distribution. RESULTS: Butyrate tre atment produced a dose-dependent inhibition of cellular proliferation and changes in morphology, GFAP staining, and c-myc expression consist ent with a differentiation response. Detailed flow cytometric studies, including subpopulation analysis, showed that during 72 hours of trea tment with 2 mmol/L butyrate, mean GFAP fluorescence increased to 420% , whereas c-myc protein decreased to 45 +/- 13% and total cellular pro tein increased to 181 +/- 17%. The effects of butyrate were distinct f rom those of serum deprivation and were not simply the result of cells shifting into G(0)/G(1). CONCLUSION: The butyrate-induced responses o f the U138B cell line provide a convenient model system for studying t he molecular events accompanying the differentiation of glioblastoma c ells. Multiparameter flaw cytometry is a useful technique for characte rizing such differentiation.