BCL2 and CASP8 regulation by NF-kappaB differentially affect mitochondrial function and cell fate in antiestrogen-sensitive and -resistant breast cancer cells.
Resistance to endocrine therapies remains a major problem in the management of estrogen receptor-alpha (ER)-positive breast cancer. We show that inhibition of NF-kappaB (p65/RELA), either by overexpression of a mutant IkappaB (IkappaBSR) or a small-molecule inhibitor of NF-kappaB (parthenolide; IC(50)=500 nM in tamoxifen-resistant cells), synergistically restores sensitivity to 4-hydroxytamoxifen (4HT) in resistant MCF7/RR and MCF7/LCC9 cells and further sensitizes MCF-7 and MCF7/LCC1 control cells to 4HT. These effects are independent of changes in either cell cycle distribution or in the level of autophagy measured by inhibition of p62/SQSTM1 expression and cleavage of LC3. NF-kappaB inhibition restores the ability of 4HT to decrease BCL2 expression, increase mitochondrial membrane permeability, and induce a caspase-dependent apoptotic cell death in resistant cells. Each of these effects is reversed by a caspase 8 (CASP8)-specific inhibitor that blocks enzyme-substrate binding. Thus, increased activation of NF-kappaB can alter sensitivity to tamoxifen by modulating CASP8 activity, with consequent effects on BCL2 expression, mitochondrial function, and apoptosis. These data provide significant new insights into how molecular signaling affects antiestrogen responsiveness and strongly suggest that a combination of parthenolide and tamoxifen may offer a novel therapeutic approach to the management of some ER-positive breast cancers.
Nehra
Ruchi
R
Department of Oncology, Georgetown University School of Medicine, Washington, DC 20057, USA.
Riggins
Rebecca B
RB
Shajahan
Ayesha N
AN
Zwart
Alan
A
Crawford
Anatasha C
AC
Clarke
Robert
R
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002463:Cell Membrane Permeability / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D004965:Estrogen Antagonists / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D047468:Immunoprecipitation; D008156:Luciferases / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000378:metabolism*; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071456:Sequestosome-1 Protein; D015398:Signal Transduction; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology
D048868:Adaptor Proteins, Signal Transducing; C506487:ESR1 protein, human; D004965:Estrogen Antagonists; D047628:Estrogen Receptor alpha; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D013629:Tamoxifen; C016601:afimoxifene; D008156:Luciferases; D053181:Caspase 8