The purpose of this study was to characterize the effects of
sodium 4-phenylbutyrate (phenylbutyrate) on the proliferation, morphology, migration and invasiveness of
malignant glioma cells in vitro. Phenylbutyrate is a novel differentiating and cytotoxic compound used clinically with low toxicity in the treatment of
beta-thalassemia,
sickle cell anemia and
urea cycle disorders. Preliminary clinical trials testing phenylbutyrate as an anti-
cancer agent have included patients with
malignant glioma. However, little information is available regarding the effects of phenylbutyrate on
glioma cells, particularly with respect to the expression of genes important in the pathogenesis of glial
malignancy. In experiments reported here,
glioma cell lines and explant cells from a
tumor patient were exposed to 2, 4 and 8 mM phenylbutyrate and compared to untreated control cells. The effect on cellular proliferation was assessed using cell counts and
DNA flow cytometry. Changes in morphology were evaluated using
vimentin staining. Scratch and
Matrigel assays were performed to assess changes in cellular migration and invasiveness. Finally, Northern blot analysis was used to study c-myc and
urokinase expression. Phenylbutyrate was found to have dose-dependent inhibitory effects on
glioma cell proliferation, morphology, migration, invasiveness and c-myc and
urokinase expression. Mean growth-inhibitory (IC50) phenylbutyrate concentrations ranged from 0.5 mM for T98G cells to 5.0 mM for explant cells. Phenylbutyrate treatment reduced % S phase cells, increased % G0/G1 cells, and produced morphologic changes consistent with induction of differentiation. 24 hours of treatment with 4 mM phenylbutyrate resulted in a 50% reduction in migration and invasiveness. Northern blots showed a decrease in
urokinase and c-myc expression at non-cytotoxic doses. We conclude that phenylbutyrate is a promising candidate compound for treating patients with
malignant glioma.