Tunicamycin treatment induced cell death and unfolded protein response in PEF cells. (A) Tunicamycin treatment for 24 h in PEF cells induced cell death compared to the control PEF cells and (B) the cell death was dose-dependent. Data are presented as means ± SEM. *P < 0.05, **P < 0.001. (C) Tunicamycin treatment increased expression of an ER stress marker BiP in the RT-PCR analysis. (D) Three major ER stress sensors IRE1, PERK, and ATF6 were activated after TM treatment. (E) Quantification of the Western blot analysis in (D). Data were presented as means ± SD from three independent experiments.