Targeting the Unfolded Protein Response in Glioblastoma Cells with the Fusion Protein EGF-SubA
Figure 5
Acidic pH activates the UPR pathway and enhances EGF-SubA cytotoxicity.
U251 cells grown in RPMI media whose pH was adjusted to 6.7 and 7.0 with 1N HCl for 3 passages prior to performing experiments demonstrated UPR activation, as determined by PERK phosphorylation (A; pPERK), Xbp1 splicing and increased GRP78 transcription (B). (C) To determine if cells grown in acidic conditions influenced EGF-SubA cytotoxicity, a clonogenic assay was performed with U251 cells grown in normal (pH 7.4) or acidic (pH 6.7) conditions at the stated concentrations. Cell survival was significantly different between cells grown in normal and acidic pH at higher doses of EGF SubA (p<0.0001 at 2.5 pM). Each figure is a representative of three independent experiments.