FIGURE 3.

Oxidatively modified LDLs suppress the anti-MM effects of bortezomib via associated lipid hydroperoxides. A, mmLDL was pretreated with or without ebselen (EBS) plus glutathione (GSH) to reduce lipid hydroperoxides (LOOHs), as described in Section 2. LOOHs associated with the mmLDL or mmLDL pretreated with EBS + GSH (ie, LOOH-depleted mmLDL) used for the experiments in (B and C) were measured as described in Section 2. Data are expressed as the mean ± SE of the LOOH levels (nmol/mg mmLDL) from four independent pretreatments. B, Representative western blot of Ub accumulation and PARP (full length/cleaved) following exposure of U266 cells for 24 hours to 6 nM bortezomib (BTZ) and 50 μg/mL mmLDL or LOOH-depleted mmLDL. (C) Proliferation of U266 cells exposed for 48 hours to 6 nM BTZ and 50 μg/mL mmLDL or LOOH-depleted mmLDL. Proliferation of MM1R (D) and U266 (E) cells simultaneously exposed for 48 hours to 25 μM EBS and/or 6 nM BTZ and/or 50 μg/mL mmLDL. Proliferation in (C-E) was assessed by MTS assay. Data are expressed as the mean ± SE of four independent experiments performed in quadruplicate. F, Representative western blot of Ub accumulation and PARP (full length/cleaved) following exposure of U266 cells for 24 hours to 25 μM EBS and/or 6 nM BTZ and/or 50 μg/mL mmLDL. (G) Representative western blot of p-MARCKS (Ser152/156), MARCKS, BCL-2, BCL-XL, HO-1, POMP and PSMB5 following exposure of U266 cells to 50 μg/mL mmLDL for 1 to 6 hours. (H) Representative western blot of p-MARCKS (Ser152/156), MARCKS, HO-1, POMP and PSMB5 following exposure of MM1S cells to 50 μg/mL mmLDL for 1 to 24 hours