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The mechanism underlying abnormally high transcription of the glial cell line-derived neurotrophic factor (GDNF) gene in glioma cells is not clear. In this study, to assess histone H3K9 acetylation levels in promoters I and II of the gdnf gene in normal human brain tissue, low- and high-grade glioma tissues, normal rat astrocytes, and rat C6 glioblastoma cells, we employed chromatin immunoprecipitation-polymerase chain reaction (ChIP-PCR), real-time PCR, and a pGL3 dual fluorescence reporter system. We also investigated the influence of treatment with curcumin, a histone acetyltransferase inhibitor, and trichostatin A (TSA), a deacetylase inhibitor, on promoter acetylation and activity and messenger RNA (mRNA) expression level of the gdnf gene in C6 cells. Compared to normal brain tissue, H3K9 acetylation in promoters I and II of the gdnf gene increased significantly in high-grade glioma tissues but not in low-grade glioma tissues. Moreover, H3K9 promoter acetylation level of the gdnf gene in C6 cells was also remarkably higher than in normal astrocytes. In C6 cells, curcumin markedly decreased promoter II acetylation and activity and GDNF mRNA expression. Conversely, all three measurements were significantly increased following TSA treatment. Our results suggest that histone H3K9 hyperacetylation in promoter II of the gdnf gene might be one of the reasons for its abnormal high transcription in glioma cells. [ABSTRACT FROM AUTHOR]

Glial cell line-derived neurotrophic factor (GDNF), which belongs to transforming growth factor β superfamily, plays important roles in glioma pathogenesis. Gdnf mRNA is aberrantly increased in glioma cells, but the underlying transcription mechanism is unclear. Here, we found that although the base sequence in the promoter region of the gdnf gene was unchanged in glioma cells, there were significant changes in the methylation level of promoter region I ( P < 0.05) in both high- and low-grade glioma tissues. However, the methylation degree in promoter region II was notably decreased in low-grade glioma tissue compared to normal brain tissue ( P < 0.05), and the demethylation sites were mainly located in the enhancer region. Conversely, methylation was markedly increased in high-grade glioma tissue ( P < 0.05), and the sites with decreased methylation level were mainly located in the silencer region. The binding capacities of several transcriptional factors, such as activating protein 2, specificity protein 1, ETS-related gene 2, and cAMP response element binding protein, which specifically bind to regions with altered methylation status decreased along with the pathological grade of glioma, and the differences between high-grade glioma and normal brain tissue were significant ( P < 0.05). The results suggest that changes in transcriptional factor binding capacity are due to changes in promoter region methylation and might be the underlying mechanism for aberrantly high gdnf expression in glioma. [ABSTRACT FROM AUTHOR]