title: 2-Methoxy antimycin reveals a unique mechanism for Bcl-x(L) inhibition.
abstract: Overexpression of Bcl-x(L) in multiple cancers correlates with resistance to chemotherapy and radiation therapy, and provides a rationale for development of small-molecule Bcl-x(L) inhibitors. Based on knockout studies, nonneoplastic cells also require Bcl-x(L) survival functions, particularly when challenged with cytotoxic agents. We analyze the selective cytotoxicity of one Bcl-x(L) inhibitor, 2-methoxy antimycin A, toward cells with excess exogenous Bcl-x(L) in isogenic cell line pairs. This selectivity, characteristic of a gain-of-function mechanism, is not shared by other known Bcl-x(L) inhibitors, including BH3I-2, HA14-1, ABT-737, gossypol, or the stapled BH3 helical peptide SAHB-BID. We show that Bcl-x(L) overexpression induces a shift in energy metabolism from oxidative phosphorylation to glycolysis. Treatment with 2-methoxy antimycin A acutely reverses the metabolic effects of Bcl-x(L), causing mitochondrial hyperpolarization and a progressive increase in mitochondrial NAD(P)H. We identify an additional small-molecule Bcl-x(L) inhibitor, NSC 310343, establishing a class of Bcl-x(L) inhibitors with gain-of-function activity. In contrast to other Bcl-x(L) inhibitors, combining gain-of-function Bcl-x(L) inhibitors with a standard inducer of apoptosis, staurosporine, enhances selective cytotoxicity toward Bcl-x(L)-overexpressing cells. These results provide an example of the intersection of bioenergetic metabolism and Bcl-x(L) functions and suggest a metabolic basis for the gain-of-function mechanism of Bcl-x(L) inhibitors.
authors.affiliation: Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue D2-190, Seattle, WA 98109, USA.
authors.forename: Pamela S
authors.initials: PS
authors.lastname: Schwartz
authors.forename: Michael K
authors.initials: MK
authors.lastname: Manion
authors.forename: Christine B
authors.initials: CB
authors.lastname: Emerson
authors.forename: John S
authors.initials: JS
authors.lastname: Fry
authors.forename: Craig M
authors.initials: CM
authors.lastname: Schulz
authors.forename: Ian R
authors.initials: IR
authors.lastname: Sweet
authors.forename: David M
authors.initials: DM
authors.lastname: Hockenbery
mesh_terms: D000818:Animals; D000968:Antimycin A / Q000031:analogs & derivatives* / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004357:Drug Synergism; D004734:Energy Metabolism / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D005947:Glucose / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010641:Phenotype; D051381:Rats; D019311:Staurosporine / Q000494:pharmacology; D051020:bcl-X Protein / Q000037:antagonists & inhibitors*
chemical_list: C522799:2-methoxyantimycin; D051020:bcl-X Protein; C032456:antimycin; D019344:Lactic Acid; D009249:NADP; D000968:Antimycin A; D019311:Staurosporine; D005947:Glucose