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1.
Mol Cancer Ther ; 13(6): 1625-35, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24672057

RESUMO

MLN4924 is an investigational small-molecule inhibitor of the Nedd8-activating enzyme currently in phase I clinical trials. MLN4924 induces DNA damage via rereplication in most cell lines. This distinct mechanism of DNA damage may affect its ability to combine with standard-of-care agents and may affect the clinical development of MLN4924. As such, we studied its interaction with other DNA-damaging agents. Mitomycin C, cisplatin, cytarabine, UV radiation, SN-38, and gemcitabine demonstrated synergy in combination with MLN4924 in vitro. The combination of mitomycin C and MLN4924 was shown to be synergistic in a mouse xenograft model. Importantly, depletion of genes within the ataxia telangiectasia and Rad3 related (ATR) and BRCA1/BRCA2 pathways, chromatin modification, and transcription-coupled repair reduced the synergy between mitomycin C and MLN4924. In addition, comet assay demonstrated increased DNA strand breaks with the combination of MLN4924 and mitomycin C. Our data suggest that mitomycin C causes stalled replication forks, which when combined with rereplication induced by MLN4924 results in frequent replication fork collisions, leading to cell death. This study provides a straightforward approach to understand the mechanism of synergy, which may provide useful information for the clinical development of these combinations.


Assuntos
Proteína BRCA1/genética , Proteína BRCA2/genética , Ciclopentanos/administração & dosagem , Sinergismo Farmacológico , Mitomicina/administração & dosagem , Pirimidinas/administração & dosagem , Enzimas Ativadoras de Ubiquitina/antagonistas & inibidores , Animais , Apoptose/efeitos dos fármacos , Proteínas Mutadas de Ataxia Telangiectasia/genética , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Proteína BRCA1/metabolismo , Proteína BRCA2/metabolismo , Linhagem Celular Tumoral , Cromatina/efeitos dos fármacos , Cromatina/genética , Dano ao DNA/efeitos dos fármacos , Humanos , Camundongos , Enzimas Ativadoras de Ubiquitina/genética , Raios Ultravioleta , Ensaios Antitumorais Modelo de Xenoenxerto
2.
Cancer Res ; 73(1): 225-34, 2013 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-23100467

RESUMO

MLN4924 is an investigational small-molecule inhibitor of the NEDD8-activating enzyme (NAE) in phase I clinical trials. NAE inhibition prevents the ubiquitination and proteasomal degradation of substrates for cullin-RING ubiquitin E3 ligases that support cancer pathophysiology, but the genetic determinants conferring sensitivity to NAE inhibition are unknown. To address this gap in knowledge, we conducted a genome-wide siRNA screen to identify genes and pathways that affect the lethality of MLN4924 in melanoma cells. Of the 154 genes identified, approximately one-half interfered with components of the cell cycle, apoptotic machinery, ubiquitin system, and DNA damage response pathways. In particular, genes involved in DNA replication, p53, BRCA1/BRCA2, transcription-coupled repair, and base excision repair seemed to be important for MLN4924 lethality. In contrast, genes within the G(2)-M checkpoint affected sensitivity to MLN4924 in colon cancer cells. Cell-cycle analysis in melanoma cells by flow cytometry following RNAi-mediated silencing showed that MLN4924 prevented the transition of cells from S-G(2) phase after induction of rereplication stress. Our analysis suggested an important role for the p21-dependent intra-S-phase checkpoint and extensive rereplication, whereas the ATR-dependent intra-S-phase checkpoint seemed to play a less dominant role. Unexpectedly, induction of the p21-dependent intra-S-phase checkpoint seemed to be independent of both Cdt1 stabilization and ATR signaling. Collectively, these data enhance our understanding of the mechanisms by which inhibition of NEDD8-dependent ubiquitination causes cell death, informing clinical development of MLN4924.


Assuntos
Antineoplásicos/farmacologia , Ciclopentanos/farmacologia , Dano ao DNA/efeitos dos fármacos , Melanoma/metabolismo , Pirimidinas/farmacologia , Ubiquitinas/metabolismo , Western Blotting , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Citometria de Fluxo , Humanos , Proteína NEDD8 , Reação em Cadeia da Polimerase
3.
Mol Cell Proteomics ; 10(11): M111.009183, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21873567

RESUMO

Cullin-RING ubiquitin ligases (CRLs) are responsible for the ubiquitination of many cellular proteins, thereby targeting them for proteasomal degradation. In most cases the substrates of the CRLs have not been identified, although many of those that are known have cancer relevance. MLN4924, an investigational small molecule that is a potent and selective inhibitor of the Nedd8-activating enzyme (NAE), is currently being explored in Phase I clinical trials. Inhibition of Nedd8-activating enzyme by MLN4924 prevents the conjugation of cullin proteins with NEDD8, resulting in inactivation of the entire family of CRLs. We have performed stable isotope labeling with amino acids in cell culture analysis of A375 melanoma cells treated with MLN4924 to identify new CRL substrates, confidently identifying and quantitating 5122-6012 proteins per time point. Proteins such as MLX, EID1, KLF5, ORC6L, MAGEA6, MORF4L2, MRFAP1, MORF4L1, and TAX1BP1 are rapidly stabilized by MLN4924, suggesting that they are novel CRL substrates. Proteins up-regulated at later times were also identified and siRNA against their corresponding genes were used to evaluate their influence on MLN4924-induced cell death. Thirty-eight proteins were identified as being particularly important for the cytotoxicity of MLN4924. Strikingly, these proteins had roles in cell cycle, DNA damage repair, and ubiquitin transfer. Therefore, the combination of RNAi with stable isotope labeling with amino acids in cell culture provides a paradigm for understanding the mechanism of action of novel agents affecting the ubiquitin proteasome system and a path to identifying mechanistic biomarkers.


Assuntos
Ciclopentanos/farmacologia , Proteoma/metabolismo , Pirimidinas/farmacologia , Enzimas Ativadoras de Ubiquitina/antagonistas & inibidores , Linhagem Celular Tumoral , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Técnicas de Silenciamento de Genes , Humanos , Cinética , Fenótipo , Complexo de Endopeptidases do Proteassoma/metabolismo , Estabilidade Proteica , Proteólise , Proteoma/genética , Proteômica , Interferência de RNA , Enzimas Ativadoras de Ubiquitina/metabolismo , Ubiquitinação
4.
Cancer Res ; 70(11): 4318-26, 2010 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-20460535

RESUMO

Multiple pathways have been proposed to explain how proteasome inhibition induces cell death, but mechanisms remain unclear. To approach this issue, we performed a genome-wide siRNA screen to evaluate the genetic determinants that confer sensitivity to bortezomib (Velcade (R); PS-341). This screen identified 100 genes whose knockdown affected lethality to bortezomib and to a structurally diverse set of other proteasome inhibitors. A comparison of three cell lines revealed that 39 of 100 genes were commonly linked to cell death. We causally linked bortezomib-induced cell death to the accumulation of ASF1B, Myc, ODC1, Noxa, BNIP3, Gadd45alpha, p-SMC1A, SREBF1, and p53. Our results suggest that proteasome inhibition promotes cell death primarily by dysregulating Myc and polyamines, interfering with protein translation, and disrupting essential DNA damage repair pathways, leading to programmed cell death.


Assuntos
Antineoplásicos/farmacologia , Ácidos Borônicos/farmacologia , Morte Celular/efeitos dos fármacos , Inibidores de Proteases/farmacologia , Inibidores de Proteassoma , Pirazinas/farmacologia , RNA Interferente Pequeno/genética , Bortezomib , Morte Celular/genética , Neoplasias do Colo/tratamento farmacológico , Neoplasias do Colo/genética , Neoplasias do Colo/metabolismo , Neoplasias do Colo/patologia , Dano ao DNA , Técnicas de Silenciamento de Genes , Células HCT116 , Células HeLa , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Melanoma/tratamento farmacológico , Melanoma/genética , Melanoma/metabolismo , Melanoma/patologia , Proteínas Serina-Treonina Quinases/biossíntese , Proteínas Serina-Treonina Quinases/genética , Proteínas Proto-Oncogênicas c-myc/biossíntese , Proteínas Proto-Oncogênicas c-myc/genética , Ribossomos/efeitos dos fármacos , Serina-Treonina Quinases TOR , Transfecção
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