HIF-1α and GPER are involved in the hypoxia-induced transcriptional activation of VEGF. (a) The mRNA expression of VEGF is up-regulated in CAFs and SkBr3 cells treated with 100 μM CoCl2, as evaluated by real-time PCR. Values are normalized to the 18S expression and shown as fold changes of mRNA expression induced by CoCl2 compared to cells treated with vehicle (-). Columns, mean of three independent experiments; bars, SD. (b) The VEGF promoter plasmid (pVEGF) is transactivated in CAFs and SkBr3 cells treated with 100 μM CoCl2 for 12 h (b) or exposed to low oxygen tension (2% O2) for 12 h (c). The transactivation of the VEGF promoter observed in SkBr3 cells treated for 12 h with 100 μM CoCl2 is abrogated by silencing HIF-1α (d) or GPER expression (e). The luciferase activities were normalized to the internal transfection control and values of cells receiving vehicle or cultured under normoxia were set as one-fold induction upon which the activities induced by CoCl2 treatment or hypoxia were calculated. Each data point represents the mean ± SD of three independent experiments performed in triplicate. (○), (●) P < 0.05 for cells receiving vehicle (-) or cultured under normoxia vs cells treated with CoCl2 or cells cultured under hypoxia.