GFAP GENE EXPRESSION IN HUMAN GLIOMA CELL

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We have analyzed GFAP expression through successive passages of GFAP-positive human glioma cell line by using the immunohistochemistry and Northern blot hybridization. In one cell line (Case 1), the cultured cells showed stable expression of GFAP protein and mRNA from early to later passage levels. In the other cell line (Case 2), GFAP expression was shown to be less stable. At early passage, nearly 100% of the cultured cells displayed intense GFAP immunoreactivity. After passage 30, however, weakly to negatively stained cells increased gradually in number, and by passage 100, almost all cells had become negative for GFAP. A similar change in GFAP immunoreactivity during successive passages was also observed in each of 7 GFAP-positive clones isolated from this cell line at passage 30 and 50, suggesting that each cell had a tendency to reduce and finally stop its GFAP expression. Northern blot studies revealed that GFAP mRNA also change concomitantly in the parental and clonal cell lines, suggesting a regulatory change at the transcriptional level.GFAP mRNA have been analyzed in materials of one astrocytoma case, and of one anaplastic glioma case using in situ hybridization technique. Anti-sense oligomer specific for GFAP cDNA was selected from 3' non-coding region. The use of this probe with low stringency showed 3.4-kb band in human glioma cell lines by Northern blot hybridization. The positive grains specific for GFAP mRNA were distributed in Bergmann's glia in normal cerebellum, and in astrocytoma tissues, but not in anaplastic glioma tissues.