GDNF and glioma: To determine whether histone hyperacetylation in the Egr-1 binding sites of GDNF promoter II is necessary for Egr-1 to regulate enhanced GDNF transcription in glioma cells, a C6 glioma cell model with histone hypoacetylation in the Egr-1 binding sites of GDNF promoter II was established by treatment with curcumin (Figure 6A).