title: Synergistic induction of apoptosis in multiple myeloma cells by bortezomib and hypoxia-activated prodrug TH-302, in vivo and in vitro.
abstract: Recently, we showed that hypoxia is a critical microenvironmental factor in multiple myeloma, and that the hypoxia-activated prodrug TH-302 selectively targets hypoxic multiple myeloma cells and improves multiple disease parameters in vivo. To explore approaches for sensitizing multiple myeloma cells to TH-302, we evaluated in this study the antitumor effect of TH-302 in combination with the clinically used proteasome inhibitor bortezomib. First, we show that TH-302 and bortezomib synergistically induce apoptosis in multiple myeloma cell lines in vitro. Second, we confirm that this synergism is related to the activation of caspase cascades and is mediated by changes of Bcl-2 family proteins. The combination treatment induces enhanced cleavage of caspase-3/8/9 and PARP, and therefore triggers apoptosis and enhances the cleavage of proapoptotic BH3-only protein BAD and BID as well as the antiapoptotic protein Mcl-1. In particular, TH-302 can abrogate the accumulation of antiapoptotic Mcl-1 induced by bortezomib, and decreases the expression of the prosurvival proteins Bcl-2 and Bcl-xL. Furthermore, we found that the induction of the proapoptotic BH3-only proteins PUMA (p53-upregulated modulator of apoptosis) and NOXA is associated with this synergism. In response to the genotoxic and endoplasmic reticulum stresses by TH-302 and bortezomib, the expression of PUMA and NOXA were upregulated in p53-dependent and -independent manners. Finally, in the murine 5T33MMvv model, we showed that the combination of TH-302 and bortezomib can improve multiple disease parameters and significantly prolong the survival of diseased mice. In conclusion, our studies provide a rationale for clinical evaluation of the combination of TH-302 and bortezomib in patients with multiple myeloma.
authors.affiliation: Corresponding Author: Karin Vanderkerken, Department of Hematology and Immunology, Myeloma Center Brussels, Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium. karin.vanderkerken@vub.ac.be.
authors.forename: Jinsong
authors.initials: J
authors.lastname: Hu
authors.forename: Els
authors.initials: E
authors.lastname: Van Valckenborgh
authors.forename: Dehui
authors.initials: D
authors.lastname: Xu
authors.forename: Eline
authors.initials: E
authors.lastname: Menu
authors.forename: Hendrik
authors.initials: H
authors.lastname: De Raeve
authors.forename: Elke
authors.initials: E
authors.lastname: De Bruyne
authors.forename: Elke
authors.initials: E
authors.lastname: De Bryune
authors.forename: Song
authors.initials: S
authors.lastname: Xu
authors.forename: Ben
authors.initials: B
authors.lastname: Van Camp
authors.forename: Damian
authors.initials: D
authors.lastname: Handisides
authors.forename: Charles P
authors.initials: CP
authors.lastname: Hart
authors.forename: Karin
authors.initials: K
authors.lastname: Vanderkerken
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004195:Disease Models, Animal; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology*; D009593:Nitroimidazoles / Q000494:pharmacology*; D010752:Phosphoramide Mustards / Q000494:pharmacology*; D011719:Pyrazines / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D001897:Boronic Acids; D009593:Nitroimidazoles; D010752:Phosphoramide Mustards; D011719:Pyrazines; C552526:TH 302; D000069286:Bortezomib