TGF-alpha differentially regulates GFAP, vimentin, and nestin gene expression in U-373 MG glioblastoma cells: Correlation with cell shape and motility

To begin understanding the regulation and biological significance of change s in the expression of intermediate filament proteins in astrocytic tumors, we have recently shown that TGF-alpha alters the protein level of glial fi brillary acidic protein (GFAP), nestin, and vimentin in U-373 MG glioblasto ma cells, Here, we have determined the molecular mechanisms regulating thes e changes. In addition, to evaluate the significance of these changes we ha ve examined whether TGF-alpha affects various cellular properties related t o differentiation. Our results show that, in U-373 MG cells treated with TG F-alpha, GFAP gene transcription, mRNA level, and specific protein synthesi s decrease by similar to 50%. This suggests that, in U-373 MG cells, TGF-al pha down-regulates the expression of this marker of astrocytic differentiat ion at the transcriptional level, resulting in decreased GFAP mRNA level an d specific protein synthesis. In contrast, TGF-alpha does not change viment in gene transcription, but increases by about 50% the transcription of the gene for nestin, a marker for undifferentiated astrocytic precursors. This differential regulation of GFAP, nestin, and vimentin gene expression indic ates that TGF-alpha induces further dedifferentiation of U-373 MG cells. Th is notion is also supported by our findings that TGF-alpha increases the mo tility of U-373 MG cells and induces a less stellate morphology. (C) 2000 A cademic Press.