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Blocking NF-?B and Akt by Hsp90 inhibition sensitizes Smac mimetic compound 3-induced extrinsic apoptosis pathway and results in synergistic cancer cell death.

ABSTRACT: NF-?B and Akt are two main cell survival pathways that attenuate the anticancer efficacy of therapeutics. Our previous studies demonstrated that the Smac mimetic compound 3 (SMC3) specifically suppresses c-IAP1 and induces TNF-? autocrine to kill cancer cells. However, SMC3 also induces a cell survival signal through NF-?B activation. In this report, we further found that SMC3 potently activates Akt, which inhibits SMC3-induced cancer cell death. Strikingly, concurrent blocking NF-?B and Akt resulted in a significantly potentiated cytotoxicity. Because heat shock protein 90 (Hsp90) plays an important role in maintaining the integrity of both the NF-?B and Akt pathways in cancer cells, we examined if suppression of Hsp90 is able to potentiate SMC3-induced cancer cell death. The results show that targeting Hsp90 does not interfere with SMC3-induced c-IAP1 degradation and TNF-? autocrine, the key processes for SMC3-induced cancer cell apoptosis. However, Hsp90 inhibitors effectively blocked SMC3-induced NF-?B activation through degradation of RIP1 and IKK?, two key components of the NF-?B activation pathway, and reduced both the constitutive and SMC3-induced Akt activity through degradation of the Akt protein. Consistently, with the co-treatment of SMC3 and Hsp90 inhibitors, apoptosis was markedly sensitized and a synergistic cytotoxicity was observed. The results suggest that concurrent targeting c-IAP1 and Hsp90 by combination of SMC3 and Hsp90 inhibitors is an effective approach for improving the anticancer value of SMC3.

SUBMITTER: Bai L

PROVIDER: S-EPMC3079540 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Blocking NF-κB and Akt by Hsp90 inhibition sensitizes Smac mimetic compound 3-induced extrinsic apoptosis pathway and results in synergistic cancer cell death.

Bai Lang L Xu Shanling S Chen Wenshu W Li Zi Z Wang Xia X Tang Hong H Lin Yong Y

Apoptosis : an international journal on programmed cell death 20110101 1

NF-κB and Akt are two main cell survival pathways that attenuate the anticancer efficacy of therapeutics. Our previous studies demonstrated that the Smac mimetic compound 3 (SMC3) specifically suppresses c-IAP1 and induces TNF-α autocrine to kill cancer cells. However, SMC3 also induces a cell survival signal through NF-κB activation. In this report, we further found that SMC3 potently activates Akt, which inhibits SMC3-induced cancer cell death. Strikingly, concurrent blocking NF-κB and Akt res ...[more]

PMID: 20862547

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Project description:BACKGROUND:Chemotherapy is the standard treatment for breast cancer; however, the response to chemotherapy is disappointingly low. Here, we investigated the alternative therapeutic efficacy of novel combination treatment with necroptosis-inducing small molecules to overcome chemotherapeutic resistance in tyrosine aminoacyl-tRNA synthetase (YARS)-positive breast cancer. METHODS:Pre-chemotherapeutic needle biopsy of 143 invasive ductal carcinomas undergoing the same chemotherapeutic regimen was subjected to proteomic analysis. Four different machine learning algorithms were employed to determine signature protein combinations. Immunoreactive markers were selected using three common candidate proteins from the machine-learning algorithms and verified by immunohistochemistry using 123 cases of independent needle biopsy FFPE samples. The regulation of chemotherapeutic response and necroptotic cell death was assessed using lentiviral YARS overexpression and depletion 3D spheroid formation assay, viability assays, LDH release assay, flow cytometry analysis, and transmission electron microscopy. The ROS-induced metabolic dysregulation and phosphorylation of necrosome complex by YARS were assessed using oxygen consumption rate analysis, flow cytometry analysis, and 3D cell viability assay. The therapeutic roles of SMAC mimetics (LCL161) and a pan-BCL2 inhibitor (ABT-263) were determined by 3D cell viability assay and flow cytometry analysis. Additional biologic process and protein-protein interaction pathway analysis were performed using Gene Ontology annotation and Cytoscape databases. RESULTS:YARS was selected as a potential biomarker by proteomics-based machine-learning algorithms and was exclusively associated with good response to chemotherapy by subsequent immunohistochemical validation. In 3D spheroid models of breast cancer cell lines, YARS overexpression significantly improved chemotherapy response via phosphorylation of the necrosome complex. YARS-induced necroptosis sequentially mediated mitochondrial dysfunction through the overproduction of ROS in breast cancer cell lines. Combination treatment with necroptosis-inducing small molecules, including a SMAC mimetic (LCL161) and a pan-BCL2 inhibitor (ABT-263), showed therapeutic efficacy in YARS-overexpressing breast cancer cells. CONCLUSIONS:Our results indicate that, before chemotherapy, an initial screening of YARS protein expression should be performed, and YARS-positive breast cancer patients might consider the combined treatment with LCL161 and ABT-263; this could be a novel stepwise clinical approach to apply new targeted therapy in breast cancer patients in the future.

Project description:As inhibitor of apoptosis (IAP) proteins can regulate additional signaling pathways beyond apoptosis, we investigated the effect of the second mitochondrial activator of caspases (Smac) mimetic BV6, which antagonizes IAP proteins, on non-apoptotic functions in glioblastoma (GBM). Here, we identify non-canonical nuclear factor-?B (NF-?B) signaling and a tumor necrosis factor-? (TNF?)/TNF receptor 1 (TNFR1) autocrine/paracrine loop as critical mediators of BV6-stimulated migration and invasion of GBM cells. In addition to GBM cell lines, BV6 triggers cell elongation, migration and invasion in primary, patient-derived GBM cells at non-toxic concentrations, which do not affect cell viability or proliferation, and also increases infiltrative tumor growth in vivo underscoring the relevance of these findings. Molecular studies reveal that BV6 causes rapid degradation of cellular IAP proteins, accumulation of NIK, processing of p100 to p52, translocation of p52 into the nucleus, increased NF-?B DNA binding and enhanced NF-?B transcriptional activity. Electrophoretic mobility shift assay supershift shows that the NF-?B DNA-binding subunits consist of p50, p52 and RelB further confirming the activation of the non-canonical NF-?B pathway. BV6-stimulated NF-?B activation leads to elevated mRNA levels of TNF? and additional NF-?B target genes involved in migration (i.e., interleukin 8, monocyte chemoattractant protein 1, CXC chemokine receptor 4) and invasion (i.e., matrix metalloproteinase-9). Importantly, inhibition of NF-?B by overexpression of dominant-negative I?B? superrepressor prevents the BV6-stimulated cell elongation, migration and invasion. Similarly, specific inhibition of non-canonical NF-?B signaling by RNA interference-mediated silencing of NIK suppresses the BV6-induced cell elongation, migration and invasion as well as upregulation of NF-?B target genes. Intriguingly, pharmacological or genetic inhibition of the BV6-stimulated TNF? autocrine/paracrine loop by the TNF?-blocking antibody Enbrel or by knockdown of TNFR1 abrogates BV6-induced cell elongation, migration and invasion. By demonstrating that the Smac mimetic BV6 at non-toxic concentrations promotes migration and invasion of GBM cells via non-canonical NF-?B signaling, our findings have important implications for the use of Smac mimetics as cancer therapeutics.

Dataset Information

Blocking NF-?B and Akt by Hsp90 inhibition sensitizes Smac mimetic compound 3-induced extrinsic apoptosis pathway and results in synergistic cancer cell death.

Publications

Blocking NF-κB and Akt by Hsp90 inhibition sensitizes Smac mimetic compound 3-induced extrinsic apoptosis pathway and results in synergistic cancer cell death.

Similar Datasets

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