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Role of Apollon in human melanoma resistance to anti-tumor agents that activate the intrinsic or the extrinsic apoptosis pathways

ABSTRACT: PURPOSE: To assess the role of Apollon in melanoma resistance to intrinsic and extrinsic pathways of apoptosis and to identify strategies to reduce its expression. EXPERIMENTAL DESIGN: Expression of Apollon was assessed in melanoma cell lines and in surgical specimens.Gene expression profiling, mitochondrial depolarization, caspases activation and apoptosis assays were used to test the effect of Apollon silencing, by siRNA, on melanoma response to different anti-tumor agents. Levels of expression of Apollon and melanoma apoptosis were assessed after tumor treatment with the combination of MEK- and mTOR- inhibitors, or of anti-HLA class II mAbs and anti-tumor agents. RESULTS: Melanoma cells constitutively expressed Apollon, in-vitro and in-vivo. Extent of melanoma apoptosis correlated significantly with Apollon downmodulation upon treatment with a MEK inhibitor, a BRAFV600E-specific inhibitor or the nitrosourea fotemustine. Apollon silencing enhanced melanoma apoptosis in response to the cytotoxic drugs camptothecin, celecoxib, fotemustine and temozolomide, to MEK- and BRAFV600E-specific inhibitors, and to soluble or membrane-bound TRAIL. Mechanistically, Apollon silencing in melanoma cells promoted mitochondrial depolarization, caspase-2, -8, -9 and -3 activation and alteration in the expression of genes related to different cellular functions in response to different anti-tumor agents. Treatment of melanoma cells with combination of MEK and of mTOR inhibitors, or of HLA class II antigen-specific mAb and anti-tumor agents, promoted Apollon downmodulation, associated with enhanced apoptotic responses. CONCLUSIONS: The results suggest that Apollon is a relevant molecule in melanoma resistance to apoptosis, and that strategies aimed at downmodulating Apollon protein may improve melanoma cell death in response to anti-tumor agents that trigger the intrinsic or the extrinsic apoptosis pathways.

ORGANISM(S): Homo sapiens

PROVIDER: GSE34686 | GEO | 2012/07/11

SECONDARY ACCESSION(S): PRJNA150305

REPOSITORIES: GEO

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Project description:PURPOSE: To assess the role of Apollon in melanoma resistance to intrinsic and extrinsic pathways of apoptosis and to identify strategies to reduce its expression. EXPERIMENTAL DESIGN: Expression of Apollon was assessed in melanoma cell lines and in surgical specimens.Gene expression profiling, mitochondrial depolarization, caspases activation and apoptosis assays were used to test the effect of Apollon silencing, by siRNA, on melanoma response to different anti-tumor agents. Levels of expression of Apollon and melanoma apoptosis were assessed after tumor treatment with the combination of MEK- and mTOR- inhibitors, or of anti-HLA class II mAbs and anti-tumor agents. RESULTS: Melanoma cells constitutively expressed Apollon, in-vitro and in-vivo. Extent of melanoma apoptosis correlated significantly with Apollon downmodulation upon treatment with a MEK inhibitor, a BRAFV600E-specific inhibitor or the nitrosourea fotemustine. Apollon silencing enhanced melanoma apoptosis in response to the cytotoxic drugs camptothecin, celecoxib, fotemustine and temozolomide, to MEK- and BRAFV600E-specific inhibitors, and to soluble or membrane-bound TRAIL. Mechanistically, Apollon silencing in melanoma cells promoted mitochondrial depolarization, caspase-2, -8, -9 and -3 activation and alteration in the expression of genes related to different cellular functions in response to different anti-tumor agents. Treatment of melanoma cells with combination of MEK and of mTOR inhibitors, or of HLA class II antigen-specific mAb and anti-tumor agents, promoted Apollon downmodulation, associated with enhanced apoptotic responses. CONCLUSIONS: The results suggest that Apollon is a relevant molecule in melanoma resistance to apoptosis, and that strategies aimed at downmodulating Apollon protein may improve melanoma cell death in response to anti-tumor agents that trigger the intrinsic or the extrinsic apoptosis pathways. The human melanoma cell line Me23682 was established in our laboratory from a surgical specimen. Cells were routinely maintained in RPMI medium 1640 (Lonza, Basel, Switzerland) supplemented with 10% FBS (Lonza) and 2 mM glutamine (Lonza). Cells were maintained at 37°C in a water-saturated atmosphere of 5% CO2 in air. 3x106 cells were seeded in 10 cm dishes; after 24 hours, cells were transfected with Apollon-specific siRNA or its unrelated control (Stealth RNAi siRNA, Invitrogen Life Technologies, Camarillo, CA) at a final concentration of 75 nmol/L and then left untreated or treated with fotemustine (Muphoran, Italfarmaco, Milan, Italy) at 150 umol/L for 6 hours, or with the BRAFV600E-specific inhibitor PLX4720 (Selleck Chemicals, Houston, TX) at 500 nmol/L for 8 hours, or with the MEK inhibitor PD0325901 (Cayman Chemicals, Ann Arbor, MI) at 5 nmol/L for 8 hours. Each treatment or combination was performed in triplicate. At the end of treatment, cells were collected and RNA extracted.

Project description:Combining direct anti-tumor effects with targeting of tumor microenvironment is an attractive strategy that may lead to more effective therapies for advanced melanoma. Here, we tested whether association of TRAIL with co-targeting of MEK and PI3K/mTOR, or with MEK blockade, could have synergistic anti-melanoma activity mediated not only by induction of tumor cell death, but also by effects on the tumor microenvironment. Drug interaction analysis by the Chou-Talalay approach in a panel of 21 melanoma cell lines indicated that strong synergism could be achieved by association of the MEK1/2 inhibitor AZD6244, the PI3K/mTOR inhibitor NPV-BEZ235 and TRAIL, as well as by the AZD6244/TRAIL combination. Synergism was observed on most tumors including TRAIL- or inhibitor-resistant melanomas, irrespective of the BRAF, NRAS, p53 and PTEN status, and was explained by enhanced induction of caspase-dependent melanoma apoptosis. The AZD/BEZ/TRAIL and AZD/TRAIL combinatorial treatments induced strong modulation of key apoptosis regulators along the extrinsic and intrinsic cell death pathways, including c-FLIP down-regulation, caspase-8 cleavage, BIMs and BAXa upregulation, clusterin and Mcl-1 inhibition, enhanced mitochondrial depolarization, suppression of inhibitors of apoptosis c-IAP1, c-IAP2, XIAP and Apollon, and caspase 3/7 activation. In an in vivo model, the AZD6244/TRAIL combinatorial treatment induced highly significant growth inhibition of a TRAIL-resistant tumor associated not only with melanoma cell death, but even with suppression of pro-angiogenic molecules HIF1a, VEGFa, IL-8 and TGFb1, and with inhibition of tumor angiogenesis. These results provide a proof of principle supporting the rationale for combinatorial treatments with synergistic anti-melanoma activity based on direct and indirect anti-tumor effects. The human melanoma cell line Me13 was established in our laboratory from a surgical specimen. Cells were routinely maintained in RPMI medium 1640 (Lonza, Basel, Switzerland) supplemented with 10% FBS (Lonza) and 2 mM glutamine (Lonza). Cells were maintained at 37°C in a water-saturated atmosphere of 5% CO2 in air. 3x10^6 cells were seeded in 75 cm2 flasks; after 24 hours, cells were left untreated or treated with Selumetinib (Selleck Chemicals, Houston, TX) at 0.1 micromol/L, NVP-BEZ-235 (Selleck Chemicals, Houston, TX) at 0.1 micromol/L and sTRAIL (AdipoGen) at 25ng/ml as single drugs or in combination for 8 hours. Each treatment or combination was performed in triplicate. At the end of treatment, cells were collected and RNA extracted.

Project description:The first clinical trial testing the combination of targeted therapy with a BRAF inhibitor vemurafenib and immunotherapy with a CTLA-4 antibody ipilimumab was terminated early due to significant liver toxicities, possibly due to paradoxical activation of the MAPK pathway by BRAF inhibitors in tumors with wild type BRAF. MEK inhibitors can potentiate the MAPK inhibition in tumor, while potentially alleviating the unwanted paradoxical MAPK activation. With a mouse model of syngeneic BRAFV600E driven melanoma (SM1), we tested whether the addition of the MEK inhibitor trametinib would enhance the immunosensitization effects of the BRAF inhibitor dabrafenib. Combination of dabrafenib and trametinib with pmel-1 adoptive cell transfer (ACT) showed complete tumor regression. Bioluminescent imaging and tumor infiltrating lymphocyte (TIL) phenotyping showed increased effector infiltration to tumors with dabrafenib, trametinib or dabrafenib plus trametinib with pmel-1 ACT combination. Intracellular IFN gamma staining of the TILs and in vivo cytotoxicity studies showed trametinib was not detrimental to the effector functions in vivo. Dabrafenib increased tumor associated macrophages and T regulatory cells (Tregs) in the tumors, which can be overcome by addition of trametinib. Microarray analysis revealed increased melanoma antigen, MHC expression, and global immune-related gene upregulation with the triple combination therapy. Given the up-regulation of PD-L1 seen with dabrafenib and/or trametinib combined with antigen specific ACT, we tested the triple combination of dabrafenib, trametinib with anti-PD1 therapy, and observed superior anti-tumor effect to SM1 tumors. Our findings support the testing of these combinations in patients with BRAFV600E mutant metastatic melanoma. SM1 tumors were implanted into C57BL/6 mice. Mice were treated by ACT of pmel-1 splenocytes or C57BL/6 splenocytes as control. Pmel-1 treated mice were additionally treated with either vehicle, dabrafenib, trametinib, or combination of both drugs and control mice were treated with vehicle or combination of both drugs.

Project description:Metastatic malignant melanoma is the deadliest skin cancer type, and it is characterized by its high resistance to apoptosis. The main driving mutations in melanoma cause hyperactivation of genes within the ERK pathway, with BRAF mutations being the most frequent ones, followed by NRAS, NF1 and MEK mutations. Increasing evidence shows that the MST2/Hippo pathway is also deregulated in this cancer type. While mutations are rare, MST2/Hippo pathway core proteins expression levels are often dysregulated in melanoma. The expression of the tumour suppressor RASSF1A, a bona fide activator of the pro-apoptotic MST2 pathway, is silenced by promoter methylation in over half of melanomas and correlates with poor prognosis. Here, using mass spectrometry-based interaction proteomics we identified Second Mitochondria-derived Activator of Caspases (SMAC) as a novel LATS1 interactor. We show that RASSF1A-dependent activation of the pro-apoptotic MST2 pathway promotes LATS1-SMAC interaction and negatively regulates the anti-apoptotic signal mediated by the members of the IAP family. Moreover, proteomic experiments identified a common cluster of the apoptotic regulator that bind to SMAC and LATS1. Mechanistic analysis show that the LATS1-SMAC complex promotes XIAP ubiquitination and its subsequent degradation which ultimately results apoptosis. Importantly, we show that the oncogenic BRAFV600E mutant prevents the pro-apoptotic signal mediated by the LAST1-SMAC complex while treatment of melanoma cell lines with BRAF inhibitors promotes this complex, indicating that inhibition of the LATS1-SMAC might be necessary for BRAFV600E-driven melanoma. Finally, we show that LATS1-SMAC interaction is regulated by the SMAC mimetic Birinapant which requires the inhibition of C-IAP1 and the degradation of XIAP, indicating that the MST2/Hippo pathway is part of the mechanism of action of Birinapant. Overall, the current work shows SMAC-dependent apoptosis is regulated by the LATS1 tumour suppressor and supports the idea that LATS1 is a signalling hub that regulates the crosstalk between the MST2 pathway, the apoptotic network and the RAF/ERK pathway.

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Role of Apollon in human melanoma resistance to anti-tumor agents that activate the intrinsic or the extrinsic apoptosis pathways

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