S1, a novel pan-BH3 mimetic, induces apoptosis in Mcl-1-overexpressing cells through Bak.
Mcl-1, an anti-apoptotic Bcl-2 homolog that has a structurally divergent BH3-binding pocket, non-redundant action model, and unique characteristic of short life confers complete resistance to the BH3 mimetic ABT-737. Herein, we used S1, previously identified as a Mcl-1/Bcl-2 dual inhibitor and a pure BH3 mimetic, to explore the mechanism of Mcl-1's action and supply a strategy to challenge Mcl-1's protection. Apoptosis assay in SMMC-7721, HCT116, and K562 cells demonstrated that S1 can effectively challenge Mcl-1's anti-apoptotic effect. Notably, we discovered an unexpected dynamic change of Mcl-1 that directly correlates with resistance or commitment to apoptosis induced by both ABT-737 and S1. Co-immunoprecipitation assays demonstrated that Mcl-1 increase results from Bim trafficking from Bcl-2 to Mcl-1, while subsequent Bak released by S1 determines Mcl-1 decrease and full-blown apoptosis. Further experiments using Bak shRNA testified that Bak accounts for S1-induced apoptosis and Mcl-1 decrease. Consistently, Bax-deficient DU145 cells are sensitive to S1, whereas Bak-mutant MKN-28 cells are significantly more resistant. The in vitro model could be extended to an in vivo mouse xenograft model in which Mcl-1 confers resistance by increased protein level, and the release of Bak could serve as a biomarker of apoptosis.
State Key Laboratory of Fine Chemicals, School of Chemistry, Dalian University of Technology, People's Republic of China.
Ting
T
Song
Xilong
X
Chang
Zhichao
Z
Zhang
Yubo
Y
Liu
Xiaoyun
X
Shen
D000073:Acenaphthenes / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D001713:Biphenyl Compounds / Q000494:pharmacology; D045744:Cell Line, Tumor; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009369:Neoplasms / Q000188:drug therapy / Q000473:pathology; D009596:Nitrophenols / Q000494:pharmacology; D010446:Peptide Fragments; D010879:Piperazines / Q000494:pharmacology; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D011758:Pyrroles / Q000494:pharmacology* / Q000627:therapeutic use; D013449:Sulfonamides / Q000494:pharmacology; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism*
C557101:8-oxo-3-thiomorpholin-4-yl-8H-acenaphtho(1,2-b)pyrrole-9-carbonitrile; C501332:ABT-737; D000073:Acenaphthenes; D000970:Antineoplastic Agents; C494772:BAK1 protein, human; C474007:Bax protein (53-86); D001713:Biphenyl Compounds; C579094:Mcl1 protein, mouse; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009596:Nitrophenols; D010446:Peptide Fragments; D010879:Piperazines; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011758:Pyrroles; D013449:Sulfonamides; D050998:bcl-2 Homologous Antagonist-Killer Protein