RESUMO
Oncogenic mutations in KRAS are among the most common in cancer. Classical models suggest that loss of epithelial characteristics and the acquisition of mesenchymal traits are associated with cancer aggressiveness and therapy resistance. However, the mechanistic link between these phenotypes and mutant KRAS biology remains to be established. Here, we identify STAT3 as a genetic modifier of TGF-beta-induced epithelial to mesenchymal transition. Gene expression profiling of pancreatic cancer cells identifies more than 200 genes commonly regulated by STAT3 and oncogenic KRAS. Functional classification of the STAT3-responsive program reveals its major role in tumor maintenance and epithelial homeostasis. The signatures of STAT3-activated cell states can be projected onto human KRAS mutant tumors, suggesting that they faithfully reflect characteristics of human disease. These observations have implications for therapeutic intervention and tumor aggressiveness.
Assuntos
Neoplasias Pancreáticas , Fator de Crescimento Transformador beta , Humanos , Linhagem Celular Tumoral , Transição Epitelial-Mesenquimal/genética , Pâncreas/metabolismo , Neoplasias Pancreáticas/patologia , Proteínas Proto-Oncogênicas p21(ras)/genética , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Fator de Transcrição STAT3/genética , Fator de Transcrição STAT3/metabolismo , Fator de Crescimento Transformador beta/metabolismoRESUMO
Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest human malignancies. Advanced PDAC is considered incurable. Nearly 90% of pancreatic cancers are caused by oncogenic KRAS mutations. The mechanisms of primary or acquired resistance to KRAS inhibition are currently unknown. Here, we propose that oncogenic dependency, rather than KRAS mutation per se, plays a dominant role in the immune response to cancer, including late-stage PDAC. Classifying tumor samples according to KRAS activity scores allows accurate prediction of tumor immune composition and therapy response. Dual RAS/MAPK pathway blockade combining KRAS and MEK inhibitors is more effective than the selective KRAS inhibitor alone in attenuating MAPK activation and unblocking the influx of T cells into the tumor. Lowering KRAS activity in established tumors promotes immune infiltration, but with a limited antitumor effect, whereas combining KRAS/MEK inhibition with immune checkpoint blockade achieves durable regression in preclinical models. The results are directly applicable to stratifying human PDAC based on KRAS dependency values and immune cell composition to improve therapeutic design.
Assuntos
Carcinoma Ductal Pancreático , Neoplasias Pancreáticas , Humanos , Proteínas Proto-Oncogênicas p21(ras)/genética , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Neoplasias Pancreáticas/tratamento farmacológico , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/metabolismo , Carcinoma Ductal Pancreático/tratamento farmacológico , Carcinoma Ductal Pancreático/genética , Carcinoma Ductal Pancreático/metabolismo , Mutação , Quinases de Proteína Quinase Ativadas por Mitógeno/metabolismo , ImunidadeRESUMO
Oncogenic mutations in KRAS are among the most common in cancer. Classical models suggest that loss of epithelial characteristics and the acquisition of mesenchymal traits are associated with cancer aggressiveness and therapy resistance. However, the mechanistic link between these phenotypes and mutant KRAS biology remains to be established. Here we identify STAT3 as a genetic modifier of TGF-beta-induced epithelial to mesenchymal transition. Gene expression profiling of pancreatic cancer cells identifies more than 200 genes commonly regulated by STAT3 and oncogenic KRAS. Functional classification of STAT3 responsive program reveals its major role in tumor maintenance and epithelial homeostasis. The signatures of STAT3-activated cell states can be projected onto human KRAS mutant tumors, suggesting that they faithfully reflect characteristics of human disease. These observations have implications for therapeutic intervention and tumor aggressiveness.
RESUMO
Immune evasion is a hallmark of KRAS-driven cancers, but the underlying causes remain unresolved. Here, we use a mouse model of pancreatic ductal adenocarcinoma to inactivate KRAS by CRISPR-mediated genome editing. We demonstrate that at an advanced tumor stage, dependence on KRAS for tumor growth is reduced and is manifested in the suppression of antitumor immunity. KRAS-deficient cells retain the ability to form tumors in immunodeficient mice. However, they fail to evade the host immune system in syngeneic wild-type mice, triggering strong antitumor response. We uncover changes both in tumor cells and host immune cells attributable to oncogenic KRAS expression. We identify BRAF and MYC as key mediators of KRAS-driven tumor immune suppression and show that loss of BRAF effectively blocks tumor growth in mice. Applying our results to human PDAC we show that lowering KRAS activity is likewise associated with a more vigorous immune environment.
Assuntos
Evasão da Resposta Imune/fisiologia , Modelos Genéticos , Neoplasias Pancreáticas/imunologia , Proteínas Proto-Oncogênicas p21(ras)/genética , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Animais , Carcinoma Ductal Pancreático/genética , Carcinoma Ductal Pancreático/patologia , Citocinas/metabolismo , Modelos Animais de Doenças , Feminino , Edição de Genes , Perfilação da Expressão Gênica , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Nus , Ductos Pancreáticos/patologia , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/patologia , Proteínas Proto-Oncogênicas p21(ras)/imunologia , Transcriptoma , Neoplasias PancreáticasRESUMO
The inflammatory cytokine IL-6 is known to play a causal role in the promotion of cancer, although the underlying mechanisms remain to be completely understood. Interplay between endogenous and environmental cues determines the fate of cancer development. The Eµ-myc transgenic mouse expresses elevated levels of c-Myc in the B cell lineage and develops B cell lymphomas with associated mutations in p53 or other genes linked to apoptosis. We generated Eµ-myc mice that either lacked the IL-6 gene, or lacked the STAT3 gene specifically in B cells to determine the role of the IL-6/JAK/STAT3 pathway in tumor development. Using the Eµ-myc lymphoma mouse model, we demonstrate that IL-6 is a critical tumor promoter during early stages of B cell lymphomagenesis. IL-6 is shown to inhibit the expression of tumor suppressors, notably BIM and PTEN, and this may contribute to advancing MYC-driven B cell tumorigenesis. Several miRNAs known to target BIM and PTEN are upregulated by IL-6 and likely lead to the stable suppression of pro-apoptotic pathways early during the tumorigenic process. STAT3, a classical downstream effector of IL-6, appears dispensable for Eµ-myc driven lymphomagenesis. We conclude that the growth-promoting and anti-apoptotic mechanisms activated by IL-6 are critically involved in Eµ-myc driven tumor initiation and progression, but the B cell intrinsic expression of STAT3 is not required.
Assuntos
Interleucina-6/metabolismo , Linfoma de Células B/metabolismo , Fator de Transcrição STAT3/metabolismo , Animais , Apoptose/genética , Linfócitos B/metabolismo , Morte Celular/genética , Genes myc , Interleucina-6/imunologia , Janus Quinases/metabolismo , Linfoma/patologia , Linfoma de Células B/genética , Linfoma de Células B/patologia , Camundongos , Camundongos da Linhagem 129 , Camundongos Transgênicos , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Proteínas Proto-Oncogênicas c-myc/metabolismo , Fator de Transcrição STAT3/fisiologia , Proteína Supressora de Tumor p53/metabolismoRESUMO
The presence of tumor-infiltrating T cells is associated with favorable patient outcomes, yet most pancreatic cancers are immunologically silent and resistant to currently available immunotherapies. Here we show using a syngeneic orthotopic implantation model of pancreatic cancer that Pik3ca regulates tumor immunogenicity. Genetic silencing of Pik3ca in KrasG12D/Trp53R172H-driven pancreatic tumors resulted in infiltration of T cells, complete tumor regression, and 100% survival of immunocompetent host mice. By contrast, Pik3ca-null tumors implanted in T cell-deficient mice progressed and killed all of the animals. Adoptive transfer of tumor antigen-experienced T cells eliminated Pik3ca-null tumors in immunodeficient mice. Loss of PIK3CA or inhibition of its effector, AKT, increased the expression of MHC Class I and CD80 on tumor cells. These changes contributed to the increased susceptibility of Pik3ca-null tumors to T cell surveillance. Our results indicate that tumor cell PIK3CA-AKT signaling limits T cell recognition and clearance of pancreatic cancer cells. Strategies that target this pathway may yield an effective immunotherapy for this cancer.
Assuntos
Classe I de Fosfatidilinositol 3-Quinases/imunologia , Linfócitos do Interstício Tumoral/imunologia , Neoplasias Experimentais/imunologia , Neoplasias Pancreáticas/imunologia , Transdução de Sinais/imunologia , Linfócitos T/imunologia , Transferência Adotiva , Animais , Antígeno B7-1/genética , Antígeno B7-1/imunologia , Linhagem Celular Tumoral , Classe I de Fosfatidilinositol 3-Quinases/genética , Antígenos de Histocompatibilidade Classe I/genética , Antígenos de Histocompatibilidade Classe I/imunologia , Humanos , Linfócitos do Interstício Tumoral/patologia , Camundongos , Camundongos Knockout , Camundongos SCID , Neoplasias Experimentais/genética , Neoplasias Experimentais/patologia , Neoplasias Experimentais/terapia , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/patologia , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas Proto-Oncogênicas c-akt/imunologia , Transdução de Sinais/genética , Linfócitos T/patologia , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
A dichotomy exists regarding the role of signal transducer and activator of transcription 3 (STAT3) in cancer. Functional and genetic studies demonstrate either an intrinsic requirement for STAT3 or a suppressive effect on common types of cancer. These contrasting actions of STAT3 imply context dependency. To examine mechanisms that underlie STAT3 function in cancer, we evaluated the impact of STAT3 activity in KRAS-driven lung and pancreatic cancer. Our study defines a fundamental and previously unrecognized function of STAT3 in the maintenance of epithelial cell identity and differentiation. Loss of STAT3 preferentially associates with the acquisition of mesenchymal-like phenotypes and more aggressive tumor behavior. In contrast, persistent STAT3 activation through Tyr705 phosphorylation confers a differentiated epithelial morphology that impacts tumorigenic potential. Our results imply a mechanism in which quantitative differences of STAT3 Tyr705 phosphorylation, as compared with other activation modes, direct discrete outcomes in tumor progression.
Assuntos
Neoplasias Pulmonares/genética , Neoplasias Pancreáticas/genética , Proteínas Proto-Oncogênicas p21(ras)/genética , Fator de Transcrição STAT3/metabolismo , Adenocarcinoma/genética , Animais , Carcinogênese , Diferenciação Celular , Células Epiteliais/metabolismo , Transição Epitelial-Mesenquimal , Regulação Neoplásica da Expressão Gênica , Humanos , Pulmão/citologia , Neoplasias Pulmonares/metabolismo , Camundongos , Camundongos Nus , Neoplasias Pancreáticas/metabolismo , Fosfoproteínas/fisiologia , Fator de Transcrição STAT3/química , Transativadores/fisiologia , Peixe-ZebraRESUMO
KRAS is the most commonly mutated oncogene, frequently associated with some of the deadliest forms of cancer. However, the need for potent and specific KRAS inhibitors remains unmet. Here, we evaluated the effects of selected cytotoxic agents on oncogenic KRAS signaling and drug response. The data provided new insights into the functional interaction between the KRAS and MYC pathways and revealed key differences between WT and mutant KRAS expressing cells. Systematic investigation of non-small cell lung cancer cell lines revealed that KRAS mutation can paradoxically increase the sensitivity of cells to cytotoxic agents. We identify MYC as a key regulator of the cellular stress responses and tumor cell viability as MYC expression was suppressed in drug-sensitive but not resistant cells. Furthermore, this suppression was driven by hyperactive KRAS/MAPK signaling. Our findings support a direct link between MYC and cancer cell viability, and raise the possibility that inactivation of MYC may be an effective therapeutic strategy for KRAS mutant tumors across various cancer types.
Assuntos
Carcinoma Pulmonar de Células não Pequenas/genética , Resistencia a Medicamentos Antineoplásicos/genética , Neoplasias Pulmonares/genética , Proteínas Proto-Oncogênicas c-myc/genética , Proteínas Proto-Oncogênicas p21(ras)/genética , Antineoplásicos/farmacologia , Western Blotting , Carcinoma Pulmonar de Células não Pequenas/metabolismo , Linhagem Celular Tumoral , Citotoxinas/farmacologia , Regulação Neoplásica da Expressão Gênica/genética , Humanos , Neoplasias Pulmonares/metabolismo , Análise de Sequência com Séries de Oligonucleotídeos , Proteínas Proto-Oncogênicas c-myc/metabolismo , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Transdução de Sinais/efeitos dos fármacosRESUMO
Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive, metastatic disease with limited treatment options. Factors contributing to the metastatic predisposition and therapy resistance in pancreatic cancer are not well understood. Here, we used a mouse model of KRAS-driven pancreatic carcinogenesis to define distinct subtypes of PDAC metastasis: epithelial, mesenchymal and quasi-mesenchymal. We examined pro-survival signals in these cells and the therapeutic response differences between them. Our data indicate that the initiation and maintenance of the transformed state are separable, and that KRAS dependency is not a fundamental constant of KRAS-initiated tumors. Moreover, some cancer cells can shuttle between the KRAS dependent (drug-sensitive) and independent (drug-tolerant) states and thus escape extinction. We further demonstrate that inhibition of KRAS signaling alone via co-targeting the MAPK and PI3K pathways fails to induce extensive tumor cell death and, therefore, has limited efficacy against PDAC. However, the addition of histone deacetylase (HDAC) inhibitors greatly improves outcomes, reduces the self-renewal of cancer cells, and blocks cancer metastasis in vivo. Our results suggest that targeting HDACs in combination with KRAS or its effector pathways provides an effective strategy for the treatment of PDAC.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Carcinoma Ductal Pancreático/tratamento farmacológico , Inibidores de Histona Desacetilases/farmacologia , MAP Quinase Quinase Quinases/antagonistas & inibidores , Neoplasias Pancreáticas/tratamento farmacológico , Inibidores de Fosfoinositídeo-3 Quinase , Inibidores de Proteínas Quinases/farmacologia , Animais , Carcinoma Ductal Pancreático/enzimologia , Carcinoma Ductal Pancreático/genética , Linhagem Celular Tumoral , Resistencia a Medicamentos Antineoplásicos , Genes ras , Inibidores de Histona Desacetilases/administração & dosagem , Humanos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Camundongos , Camundongos Nus , Mutação , Neoplasias Pancreáticas/enzimologia , Neoplasias Pancreáticas/genética , Inibidores de Proteínas Quinases/administração & dosagem , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Pancreatic cancer is one of the deadliest human malignancies. A striking feature of pancreatic cancer is that activating Kras mutations are found in â¼90% of cases. However, apart from a restricted population of cells expressing pancreatic and duodenal homeobox 1 (PDX1), most pancreatic cells are refractory to Kras-driven transformation. In the present study, we sought to determine which subsets of PDX1+ cells may be responsible for tumor growth. Using the Lox-Stop-Lox-KrasG12D genetic mouse model of pancreatic carcinogenesis, we isolated a population of KrasG12D-expressing PDX1+ cells with an inherent capacity to metastasize. This population of cells bears the surface phenotype of EpCAM+CD24+CD44+CD133-SCA1- and is closer in its properties to stem-like cells than to more mature cell types. We further demonstrate that the tumorigenic capacity of PDX1+ cells is limited, becoming progressively lost as the cells acquire a mature phenotype. These data are consistent with the hypothesis that the adult pancreas harbors a dormant progenitor cell population that is capable of initiating tumor growth under conditions of oncogenic stimulation. We present evidence that constitutive activation of the mitogen-activated protein kinase (MAPK/ERK) signaling and stabilization of the MYC protein are the two main driving forces behind the development of pancreatic cancer cells with stem-cell-like properties and high metastatic potential. Our results suggest that pancreatic cells bearing Kras mutation can be induced to differentiate into quasi-normal cells with suppressed tumorigenicity by selective inhibition of the MAPK/ERK/MYC signaling cascade.
Assuntos
Proteínas de Homeodomínio/metabolismo , Neoplasias Pulmonares/secundário , Sistema de Sinalização das MAP Quinases/fisiologia , Metástase Neoplásica/fisiopatologia , Neoplasias Pancreáticas/fisiopatologia , Proteínas Proto-Oncogênicas c-myc/metabolismo , Proteínas Proto-Oncogênicas p21(ras)/genética , Transativadores/metabolismo , Animais , Western Blotting , Citometria de Fluxo , Neoplasias Pulmonares/patologia , Camundongos , Camundongos Knockout , Camundongos Nus , Mutação de Sentido Incorreto/genética , Neoplasias Pancreáticas/metabolismo , Reação em Cadeia da Polimerase , Proteína Supressora de Tumor p53/genéticaRESUMO
Genetically or epigenetically defined reprogramming is a hallmark of cancer cells. However, a causal association between genome reprogramming and cancer has not yet been conclusively established. In particular, little is known about the mechanisms that underlie metastasis of cancer, and even less is known about the identity of metastasizing cancer cells. In this study, we used a model of conditional expression of oncogenic KrasG12D allele in primary mouse cells to show that reprogramming and dedifferentiation is a fundamental early step in malignant transformation and cancer initiation. Our data indicate that stable expression of activated KrasG12D confers on cells a large degree of phenotypic plasticity that predisposes them to neoplastic transformation and acquisition of stem cell characteristics. We have developed a genetically tractable model system to investigate the origins and evolution of metastatic pancreatic cancer cells. We show that metastatic conversion of KrasG12D-expressing cells that exhibit different degrees of differentiation and malignancy can be reconstructed in cell culture, and that the proto-oncogene c-Myc controls the generation of self-renewing metastatic cancer cells. Collectively, our results support a model wherein non-stem cancer cells have the potential to dedifferentiate and acquire stem cell properties as a direct consequence of oncogene-induced plasticity. Moreover, the disturbance in the normally existing dynamic equilibrium between cancer stem cells and non-stem cancer cells allows the formation of cancer stem cells with high metastatic capacity at any time during cancer progression.
Assuntos
Transdiferenciação Celular/genética , Transformação Celular Neoplásica/genética , Genes myc , Genes ras , Animais , Transformação Celular Neoplásica/patologia , Fibroblastos/metabolismo , Fibroblastos/patologia , Genes p53 , Camundongos , Camundongos Knockout , Modelos Genéticos , Metástase Neoplásica/genética , Metástase Neoplásica/patologia , Células-Tronco Neoplásicas/metabolismo , Células-Tronco Neoplásicas/patologia , Neoplasias Pancreáticas/etiologia , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/patologia , Fenótipo , Mutação PuntualRESUMO
Mice engineered to express c-Myc in B cells (Emu-myc mice) develop lethal lymphomas in which the gene encoding the p53 tumor suppressor is frequently mutated. Whether the p53 homolog p73 also functions as a tumor suppressor in vivo remains controversial. Here we have shown that p73 loss does not substantially affect disease onset and mortality in Emu-myc mice. However, it does alter the phenotype of the disease. Specifically, p73 loss decreased nodal disease and increased widespread extranodal dissemination. We further found that p53 acted as the dominant tumor suppressor during the onset of Emu-myc-driven B cell lymphomagenesis, while p73 modulated tumor dissemination and extranodal growth. Immunophenotyping and expression profiling suggested that p73 loss allowed increased maturation of malignant B cells and deregulated genes involved in lymphocyte homing and dissemination of human lymphomas. Consistent with this, p73 expression was frequently downregulated in a large cohort of human mature aggressive B cell lymphomas, and both the incidence and degree of p73 downregulation in these tumors correlated with their extranodal dissemination status. These data indicate that p73 is a modifier of Myc-driven lymphomas in mice, favoring tumor dissemination, and suggest that p73 could be a biomarker for human B cell lymphoma dissemination, a notion that can now be tested in clinicopathologic correlation studies.
Assuntos
Linfócitos B/patologia , Genes Supressores de Tumor , Linfoma de Células B/patologia , Linfoma/patologia , Proteína Supressora de Tumor p53/genética , Animais , Linfócitos B/metabolismo , Humanos , Linfoma/genética , Linfoma/metabolismo , Linfoma de Células B/genética , Linfoma de Células B/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Mutação , Proteína Supressora de Tumor p53/metabolismoRESUMO
Transcriptional silencing of the p73 gene through methylation has been demonstrated in human leukemias and lymphomas. However, the role of p73 in the malignant process remains to be explored. We show here that p73 acts as a T cell-specific tumor suppressor in a genetically defined mouse model, and that concomitant ablation of p53 and p73 predisposes mice to an increased incidence of thymic lymphomas compared to the loss of p53 alone. Our results demonstrate a causal role for loss of p73 in progression of T cell lymphomas to the stage of aggressive, disseminated disease. We provide evidence that tumorigenesis in mice lacking p53 and p73 proceeds through mechanisms involving altered patterns of gene expression, defects in early T cell development, impaired apoptosis, and the ensuing accumulation of chromosomal aberrations. Collectively, our data imply that tumor suppressive properties of p73 are highly dependent on cellular context, wherein p73 plays a major role in T cell development and neoplasia.
Assuntos
Proteínas de Ligação a DNA/genética , Deleção de Genes , Linfoma/metabolismo , Proteínas Nucleares/genética , Linfócitos T/citologia , Proteínas Supressoras de Tumor/genética , Animais , Apoptose , Aberrações Cromossômicas , Metilação de DNA , Inativação Gênica , Genes Supressores de Tumor , Predisposição Genética para Doença , Camundongos , Camundongos Knockout , Hibridização de Ácido Nucleico , Linfócitos T/metabolismo , Proteína Tumoral p73 , Proteína Supressora de Tumor p53/genéticaRESUMO
To better understand the role of E2F1 in tumor formation, we analyzed spontaneous tumorigenesis in p53(-/-)E2F1(+/+) and p53(-/-)E2F1(-/-) mice. We show that the combined loss of p53 and E2F1 leads to an increased incidence of sarcomas and carcinomas compared to the loss of p53 alone. E2F1-deficient tumors show wide chromosomal variation, indicative of genomic instability. Consistent with this, p53(-/-)E2F1(-/-) primary fibroblasts have a reduced capacity to maintain genomic stability when exposed to S-phase inhibitors or genotoxic drugs. A major mechanism of E2F1's contribution to genomic integrity lies in mediating stabilization and engagement of the Rb protein.
Assuntos
Fator de Transcrição E2F1/fisiologia , Neoplasias Experimentais/genética , Proteína do Retinoblastoma/metabolismo , Proteínas Supressoras de Tumor/fisiologia , Animais , Células Cultivadas , Dano ao DNA , Fator de Transcrição E2F1/genética , Camundongos , Camundongos Knockout , Neoplasias Experimentais/epidemiologia , Fenótipo , Proteína Supressora de Tumor p53/genética , Proteínas Supressoras de Tumor/genéticaRESUMO
Previous studies showed that p53 plays a central role in G1 and DNA damage checkpoints, thus contributing to genomic stability. We show here that p73 also plays a role in genomic integrity but this mechanism is manifest only when p53 is lost. Isolated p73 loss in primary cells does not induce genomic instability. Instead, it results in impaired proliferation and premature senescence due to compensatory activation of p53. Combined loss of p73 and p53 rescues these defects, but at the expense of exacerbated genomic instability. This leads to rapid increase in polyploidy and aneuploidy, markedly exceeding that of p53 loss alone. Constitutive deregulation of cyclin-Cdk activities and excess failure of the G2/M DNA damage checkpoint appear to fuel increased ploidy abnormalities upon p53/p73 loss, while primary mitotic defects do not play a causal role. These data indicate that p73 is essential for suppressing polyploidy and aneuploidy when p53 is inactivated.
Assuntos
Aneuploidia , Proteínas de Ligação a DNA/metabolismo , Proteínas Nucleares/metabolismo , Poliploidia , Proteína Supressora de Tumor p53/deficiência , Proteínas Supressoras de Tumor/metabolismo , Animais , Proteína Quinase CDC2/metabolismo , Transformação Celular Neoplásica , Senescência Celular , Quinase 2 Dependente de Ciclina/metabolismo , Dano ao DNA , Fase G2 , Instabilidade Genômica/genética , Camundongos , Mitose , Proteína Tumoral p73RESUMO
Macrophage migration inhibitory factor (MIF) is a ubiquitously expressed pro-inflammatory mediator that has also been implicated in the process of oncogenic transformation and tumor progression. We used a genetic approach to show that deletion of the MIF gene in mice has several major consequences for the proliferative and transforming properties of cells. MIF-deficient cells exhibit increased resistance to oncogenic transformation. The transformation defects associated with MIF deficiency can be overcome through concomitant inactivation of the p53 and Rb/E2F tumor suppressor pathways. We have produced compelling evidence that the effects of MIF on cell survival and tumorigenesis are mediated through overlapping pathways, wherein MIF and p53 functionally antagonize each other in the cell. However, the involvement of MIF in p53 function is secondary to p53-independent mechanisms controlling protein stability, DNA damage checkpoints, and the integrity of the genome. Given the broad spectrum of cell types that normally express MIF and its elevated levels at sites of chronic inflammation, this pathway may be generic for many early stage tumors.
RESUMO
Proper repair of DNA damage is critical for protecting genomic stability, cellular viability and suppression of tumorigenesis. Both p53-dependent and p53-independent pathways have evolved to coordinate the cellular response following DNA damage. In this review, we highlight the importance of the ubiquitously expressed protein macrophage migration inhibitory factor (MIF) for an appropriate response to DNA damage. We discuss the mechanisms by which MIF affects the activity of the ubiquitin-proteasome system, and how this impacts on the integrity of the genome and on cancer.
Assuntos
Ciclo Celular , Dano ao DNA/fisiologia , Fatores Inibidores da Migração de Macrófagos/fisiologia , Complexo de Endopeptidases do Proteassoma/metabolismo , Animais , Ciclo Celular/genética , Ciclo Celular/fisiologia , Fase G2 , Genes cdc , Humanos , Hibridização in Situ Fluorescente , Fatores Inibidores da Migração de Macrófagos/genética , Modelos Biológicos , Neoplasias/genética , Neoplasias/metabolismo , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismo , Ubiquitina/metabolismoRESUMO
Recent studies demonstrated that proinflammatory migration inhibitory factor(MIF) blocks p53-dependent apoptosis and interferes with the tumor suppressor activity of p53. To explore the mechanism underlying this MIF-p53 relationship, we studied spontaneous tumorigenesis in genetically matched p53-/- and MIF-/-p53-/- mice. We show that the loss of MIF expression aggravates the tumor-prone phenotype of p53-/- mice and predisposes them to a broader tumor spectrum, including B-cell lymphomas and carcinomas. Impaired DNA damage response is at the root of tumor predisposition of MIF-/-p53-/- mice. We provide evidence that MIF plays a role in regulating the activity of Cul1-containing SCF ubiquitin ligases. The loss of MIF expression uncouples Chk1/Chk2-responsive DNA damage checkpoints from SCF-dependent degradation of key cell-cycle regulators such as Cdc25A, E2F1 and DP1, creating conditions for the genetic instability of cells. These MIF effects depend on its association with the Jab1/CSN5 subunit of the COP9/CSN signalosome. Given that CSN plays a central role in the assembly of SCF complexes in vivo, regulation of Jab1/CSN5 by MIF is required to sustain optimal composition and function of the SCF complex.
Assuntos
Ciclo Celular/genética , Dano ao DNA , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Oxirredutases Intramoleculares/metabolismo , Fatores Inibidores da Migração de Macrófagos/metabolismo , Neoplasias/metabolismo , Peptídeo Hidrolases/metabolismo , Proteínas Ligases SKP Culina F-Box/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Animais , Complexo do Signalossomo COP9 , Células Cultivadas , Quinase 1 do Ponto de Checagem , Instabilidade Genômica/genética , Immunoblotting , Hibridização in Situ Fluorescente , Oxirredutases Intramoleculares/genética , Fatores Inibidores da Migração de Macrófagos/genética , Camundongos , Camundongos Knockout , Neoplasias/genética , Proteínas Quinases/metabolismoRESUMO
Complex proapoptotic functions are essential for the tumor suppressor activity of p53. We recently described a novel transcription-independent mechanism that involves a rapid proapoptotic action of p53 at the mitochondria and executes the shortest known circuitry of p53 death signaling. Here, we examine if this p53-dependent mitochondrial program could be exploited for tumor suppression in vivo. To test this, we engage Emu-Myc transgenic mice, a well-established model of p53-dependent lymphomagenesis. We show that exclusive delivery of p53 to the outer mitochondrial membrane confers a significant growth disadvantage on Emu-Myc-transformed B-cells of p53-deficient or alternate reading frame-deficient genotypes, resulting in efficient induction of apoptosis and impinged proliferation. Conversely, normal cells from thymus, spleen, and bone marrow showed poor infectivity with these viruses. This proof-of-principle experiment shows that exclusive reliance on the direct mitochondrial program exerts a significant tumor suppressor activity in vivo. Our in vivo data on the direct mitochondrial apoptotic p53 program lays the groundwork to further investigate its efficacy and safety and to address its possible therapeutic value in the future.