Effects of mycophenolic acid on detection of glial filaments in human and rat astrocytoma cultures.

Expression of glial fibrillary acidic protein (GFAP) was assayed in 11 glioma-derived cell cultures. Treatment of cells with an inhibitor of guanine nucleotide biosynthesis, mycophenolic acid, enhanced detection of GFAP by indirect immunofluorescence microscopy. Quantitation of GFAP and vimentin demonstrated that enhanced fluorescence occurs without an increase in the level of intermediate filament proteins. Immunoblots provided the most sensitive method for monitoring GFAP expression and showed the limitations of using immunofluorescence detection methods. GFAP was detectable in cultures derived from malignant Grade IV astrocytomas and its expression was stable during the course of the study. While mycophenolic acid has been reported to induce differentiation in leukemia cells at low concentration (D.L. Lucas et al., J. Clin. Invest., 72: 1889-1990, 1983), its effect on glioma cultures at concentrations of 100 microM was consistent with a role as an inhibitor of DNA synthesis, and as an effector of altered intermediate filament organization.