title: BH3 mimetic ABT-737 and a proteasome inhibitor synergistically kill melanomas through Noxa-dependent apoptosis.
abstract: The Bcl-2 family is important in modulating sensitivity to anticancer drugs in many cancers, including melanomas. The BH3 mimetic ABT-737 is a potent small molecule inhibitor of the anti-apoptotic proteins Bcl-2/Bcl-X(L)/Bcl-w. In this report, we examined whether ABT-737 is effective in killing melanoma cells in combination with the proteasome inhibitor MG-132, and further evaluated the mechanisms of action. Viability, morphological, and Annexin V apoptosis assays showed that ABT-737 alone exhibited little cytotoxicity, yet it displayed strong synergistic lethality when combined with MG-132. In addition, the detection of Bax/Bak activation indicated that the combination treatment synergistically induced mitochondria-mediated apoptosis. Furthermore, mechanistic analysis revealed that this combination treatment induced expression of the pro-apoptotic protein Noxa- and caspase-dependent degradation of the anti-apoptotic protein, Mcl-1. Finally, siRNA-mediated inhibition of Mcl-1 expression significantly increased sensitivity to ABT-737 in these cells, and knocking down Noxa expression protected the cells from cytotoxicity induced by the combination treatment. These findings demonstrate that ABT-737 combined with MG-132 synergistically induced Noxa-dependent mitochondrial-mediated apoptosis. In summary, this study indicates promising therapeutic potential of targeting anti-apoptotic Bcl-2 family members in treating melanoma, and it validates rational molecular approaches that target anti-apoptotic defenses when developing cancer treatments.
authors.affiliation: Department of Dermatology, School of Medicine, University of Colorado Denver, Aurora, Colorado 80010, USA.
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Miller
authors.forename: Nathaniel B
authors.initials: NB
authors.lastname: Goldstein
authors.forename: Widya U
authors.initials: WU
authors.lastname: Johannes
authors.forename: Christine H
authors.initials: CH
authors.lastname: Walton
authors.forename: Mayumi
authors.initials: M
authors.lastname: Fujita
authors.forename: David A
authors.initials: DA
authors.lastname: Norris
authors.forename: Yiqun G
authors.initials: YG
authors.lastname: Shellman
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001713:Biphenyl Compounds / Q000494:pharmacology*; D020169:Caspases / Q000502:physiology; D045744:Cell Line, Tumor; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D004357:Drug Synergism; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology*; D008545:Melanoma / Q000188:drug therapy* / Q000473:pathology; D008928:Mitochondria / Q000502:physiology; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009596:Nitrophenols / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology; D061988:Proteasome Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology*
chemical_list: C501332:ABT-737; D000970:Antineoplastic Agents; D001713:Biphenyl Compounds; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009596:Nitrophenols; C498702:PMAIP1 protein, human; D010879:Piperazines; D061988:Proteasome Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D013449:Sulfonamides; D020169:Caspases; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde