Figure 7. The downregulation of CREB3 inhibited growth of U251MG cells via activating ERS pathway. (A) PERK levels were detected by qRT-PCR in U251MG cells transfected with the NC, PERK-siRNA1 or PERK-siRNA2. (B) The levels of the ERS-related proteins p-PERK, p-eIF2α and ATF4 were detected in U251MG cells transfected with the CREB3-shRNA2, PERK-siRNA2 or co-transfected with CREB3-shRNA2 and PERK-siRNA2. (C–E) The relative levels of p-PERK (C), p-eIF2α (D) and ATF4 (E) were quantified and normalized to PERK, eIF2α and β-actin levels respectively. (F) The viability of U251MG cells was detected with a CCK-8 assay. (G, H) Apoptosis was detected with Annexin V and PI double staining, and the percentage of apoptotic cells was calculated. **P<0.01 compared with the NC group, ##P<0.01 compared with the CREB3-shRNA2 group.