Tris DBA showed additive effect with proteasome inhibitors and overcomes hypoxia-induced effects. (A) Cell viability assay of Tris DBA (0, 2 μM) under normoxic or hypoxic conditions, with or without combination of bortezomib (0, 5 nM) (i) or carfilzomib (0, 2.5 nM) (ii) for 24 h. (B) Cell cycle signaling (pRb) and apoptosis signaling (cleaved caspase 3) in MM.1S cells by Western blotting (i), of the effect of the combination of Tris DBA (0, 2 μM), with or without Bortezomib (0, 5 nM) and Carfilzomib (0, 2.5 nM), and quantification of protein expression as ratio to tubulin by densitometry (ii). (C) HIF1 expression measured as fold of MFI of AlexaFluor488-anti-HIF1 to normoxia untreated of Tris DBA (0, 2 μM) in MM.1S cells for 24 h under normoxic or hypoxic conditions (i), and flow cytometry representative histogram of HIF1α expression (AlexaFluor488) (ii). (D) Migration assay of Tris DBA (0, 2 μM) in MM.1S cells for 24 h under normoxic or hypoxic conditions.