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Global response to chemotherapy-induced apoptosis

ABSTRACT: Here we use an integrated systems-level examination of transcription, translation, and proteolysis to explore how cancer cells struggle with a chemotherapeutic drug prior to succumbing to apoptosis. As a model system we study myeloma cells exposed to the proteasome inhibitor bortezomib, a first-line clinical treatment. Despite robust transcriptional changes, unbiased quantitative proteomics detects production of only a few critical anti-apoptotic proteins against a background of general translation inhibition. Ribosome profiling further reveals potential translational regulation of stress response genes following bortezomib treatment. Once the apoptotic machinery is engaged, degradation by caspases is largely independent of changes at the transcriptional level. Moreover, previously uncharacterized non-caspase proteolytic events also participate in cellular deconstruction. As suggested by these data, we find that inhibition of the anti-apoptotic response regulator HSF1 promotes cell death by bortezomib. Thus, monitoring global cellular dynamics after chemotherapy offers in-depth insight into apoptosis and can also guide potential therapeutic combinations.

ORGANISM(S): Homo sapiens

PROVIDER: GSE48785 | GEO | 2013/10/17

SECONDARY ACCESSION(S): PRJNA211752

REPOSITORIES: GEO

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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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Global response to chemotherapy-induced apoptosis

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