OSMI-1 stimulates the ER stress response. (A) HepG2 and AML12 cells were treated with or without 20 μM of OSMI-1 for 15 h, and levels of protein-kinase-R-like endoplasmic reticulum kinase (PERK) and IRE1α were detected via Western blotting. The graphs on the right show the relative amounts of protein as fold increase. *** p < 0.005 compared with the control group. (B) HepG2 cells were treated with DOX (0.4 μM) or OSMI-1 (20 and 40 μM) for 15 h. Western blot analysis was performed to detect levels of O-GlcNAcylated proteins, PERK, IRE1α, XBP, and Bcl2. (C) HepG2 cells were treated with DOX (0.4 μM) alone or in combination with OSMI-1 (20 μM) for 15 h. Cell lysates were analyzed by Western blot using antibodies against Bcl2, Bax, cleaved PARP, caspase-3, and O-GlcNAcylated proteins. β-actin was used as an internal control. (D) HepG2 cells were treated with 0.4 μM of DOX alone or in combination with various concentrations of OSMI-1 (2, 20, or 40 μM). Levels of Bcl2 and CHOP mRNA were determined by qRT-PCR and normalized to the control sample. Values represent means ± SD (n = 6). *** p < 0.005 compared with the control group, the uncropped western blot figures in Figure S5.