ESTABLISHMENT OF HUMAN GLIOMA CELL-LINES WITH STABLE AND UNSTABLE GFAP EXPRESSION

We have established two glial fibrillary acidic protein (GFAP)-positive human glioma cell lines and have analyzed their stability of GFAP expression through successive passages 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. Stability of GFAP expression was also shown in all of 8 clones isolated from this cell line. 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 passages 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 changed concomitantly in the parental and clonal cell lines, suggesting a regulatory change at the transcriptional level. These two cell lines with different features of GFAP expression might be useful for studies on the regulatory mechanism of GFAP expression.