In vitro activity: Bardoxolone Methyl exhibits potent inhibitory activities against production of nitric oxide induced by interferon-Y in mouse macrophages with IC50 of 0.1 NM. Bardoxolone Methyl decreases the viability of leukemic HL-60, KG-1, and NB4 cells with IC50 of 0.4, 0.4, and 0.27 μM, respectively. CDDO-Me induces pro-apoptotic Bax protein, inhibits the activation of ERK1/2, and it blocks Bcl-2 phosphorylation, which contributes to the induction of apoptosis. Bardoxolone Methyl potently inhibits both constitutive and inducible NF-kappaB activated by TNF, interleukin (IL)-1beta, phorbol ester, okadaic acid, hydrogen peroxide, lipopolysaccharide, and cigarette smoke.

Kinase Assay: To determine the effect of CDDO-Me on TNF-induced IKK activation, IKK is analyzed. Briefly, the IKK complex from whole-cell extracts was precipitated with antibody against IKKα and IKKβ and then treated with protein A/G-Sepharose beads. After 2 hours, the beads are washed with lysis buffer and then resuspended in a kinase assay mixture containing 50 mmol/L HEPES (pH 7.4), 20 mmol/L MgCl2, 2 mmol/L DTT, 20 μCi [γ-32P]ATP, 10 μmol/L unlabeled ATP, and 2 μg of substrate glutathione S-transferase-IκBα (amino acids 1-54). After incubation at 30°C for 30 minutes, the reaction is terminated by boiling with SDS sample buffer for 5 minutes. Finally, the protein is resolved on 10% SDS-PAGE, the gel is dried, and the radioactive bands are visualized with a Storm820. To determine the total amounts of IKK-α and IKK-β in each sample, 50 μg of whole-cell proteins are resolved on 7.5% SDS-PAGE, electrotransferred to a nitrocellulose membrane, and then blotted with either anti-IKK-α or anti-IKK-β antibody.

Cell Assay: Leukemic cell lines are cultured at a density of 3.0 × 105 cells/mL, and AML mononuclear cells are cultured at 5 × 105 cells/mL in the presence or absence of indicated concentrations of CDDO-Me. Appropriate amounts of DMSO (final concentration less than 0.05%) are included as control. For cytotoxicity studies, 1 μM ara-C is added to the cultures. After 24 to 72 hours, viable cells are counted with the trypan blue dye exclusion method using a hematocytometer.

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