Fig. 1
High CREB expression significantly promotes GDNF transcription in U251 GBM cells. a Putative CRE sites within the human GDNF promoter II. Arrows indicate the major TSS corresponding to the GDNF promoter II. The TSS was considered + 1. The letter E indicates enhancer II, while the letter S indicates silencer II. b Comparison of mRNA levels (log2 median-centered ratio) of human CREB in NB samples (n = 10) and glioblastoma brain samples (n = 542) from TCGA brain dataset analyzed on the Oncomine® Platform. cCREB mRNA. d Protein expression in NB tissue and low- and high-grade GBM tissues as determined by real-time PCR and western blot (n = 3). eCREB mRNA. f Protein expression in NHA cells and GBM cell lines (U251 and U343) (n = 3). gCREB mRNA. h Protein expression after 72 h infection with CREB-KDs lentivirus in U251 cells (n = 3). iGDNF mRNA. j Protein expression after 72 h infection with CREB-KD1 in U251 cells (n = 3). k U251 cells were transfected with the pGDNF-Luc(− 1300/+ 149)-CRE-WT and pRL-TK plasmids after 24 h of CREB-KD1 infection; and the effect of CREB expression on the GDNF promoter II activity was assessed by dual-luciferase assay after another 48 h of incubation (n = 3). lGDNF mRNA expression after 72 h infection with CREB-OE and KCREB-OE in U251 cells (n = 3). m Binding of CREB to CRE in enhaner II (CRE-E) of GDNF promoter II after 72 h infection with CREB-OE lentivirus in U251 cells as determined by ChIP-PCR (n = 3). GAPDH was used as an internal control. All data except in (b) are mean ± SD. **P < 0.01