Figure 3

ER stress and apoptosis induction by proteasome inhibitors in combination with nelfinavir in NSCLC cells. (A) Induction of the proteins involved in the UPR upon treatment with bortezomib and carfilzomib alone or in combination with nelfinavir. Western blot analysis was performed with A549 cells at the indicated time points after 2 h of pulse treatment with proteasome inhibitors with or without nelfinavir. Representative images of three independent experiments are shown. (B) Cytotoxicity of bortezomib, carfilzomib and nelfinavir in the presence or absence of 1 µg/ml cycloheximide (CHX) pretreatment for 3 h. Cell viability was assessed 48 h after 2 h of pulse treatment with proteasome inhibitors, followed by incubation in drug-free media or nelfinavir. Data represent the mean ± SD of at least three replicates. (C) Accumulation of polyubiquitinated proteins upon treatment with bortezomib and carfilzomib alone or in combination with nelfinavir. Western blot analysis was performed with A549 cells at the indicated time points after 2 h of pulse treatment with proteasome inhibitors alone or in combination with nelfinavir. Representative images of three independent experiments are shown. (D) Induction of apoptosis upon treatment with bortezomib and carfilzomib alone or in combination with nelfinavir. Western blot analysis was performed with A549 cells at the indicated time points after 2 h of pulse treatment with proteasome inhibitors alone or in combination with nelfinavir. Representative images of three independent experiments are shown. * represents p < 0.05; *** represents p < 0.001.