RESUMO
The chromatin remodeler SMARCA4/BRG1 is a key epigenetic regulator with diverse roles in coordinating the molecular programs that underlie brain tumour development. BRG1 function in brain cancer is largely specific to the tumour type and varies further between tumour subtypes, highlighting its complexity. Altered SMARCA4 expression has been linked to medulloblastoma, low-grade gliomas such as oligodendroglioma, high-grade gliomas such as glioblastoma and atypical/teratoid rhabdoid tumours. SMARCA4 mutations in brain cancer predominantly occur in the crucial catalytic ATPase domain, which is associated with tumour suppressor activity. However, SMARCA4 is opposingly seen to promote tumourigenesis in the absence of mutation and through overexpression in other brain tumours. This review explores the multifaceted interaction between SMARCA4 and various brain cancer types, highlighting its roles in tumour pathogenesis, the pathways it regulates, and the advances that have been made in understanding the functional relevance of mutations. We discuss developments made in targeting SMARCA4 and the potential to translate these to adjuvant therapies able to enhance current methods of brain cancer treatment.
Assuntos
Neoplasias Encefálicas , Neoplasias Cerebelares , DNA Helicases , Meduloblastoma , Proteínas Nucleares , Humanos , Adenosina Trifosfatases/metabolismo , Neoplasias Encefálicas/genética , Cromatina/genética , DNA Helicases/genética , Meduloblastoma/genética , Proteínas Nucleares/genética , Fatores de Transcrição/genéticaRESUMO
Many cancer therapies operate by inducing double-strand breaks (DSBs) in cancer cells, however treatment-resistant cells rapidly initiate mechanisms to repair damage enabling survival. While the DNA repair mechanisms responsible for cancer cell survival following DNA damaging treatments are becoming better understood, less is known about the role of the epigenome in this process. Using prostate cancer cell lines with differing sensitivities to radiation treatment, we analysed the DNA methylation profiles prior to and following a single dose of radiotherapy (RT) using the Illumina Infinium HumanMethylation450 BeadChip platform. DSB formation and repair, in the absence and presence of the DNA hypomethylating agent, 5-azacytidine (5-AzaC), were also investigated using γH2A.X immunofluorescence staining. Here we demonstrate that DNA methylation is generally stable following a single dose of RT; however, a small number of CpG sites are stably altered up to 14 d following exposure. While the radioresistant and radiosensitive cells displayed distinct basal DNA methylation profiles, their susceptibility to DNA damage appeared similar demonstrating that basal DNA methylation has a limited influence on DSB induction at the regions examined. Recovery from DSB induction was also similar between these cells. Treatment with 5-AzaC did not sensitize resistant cells to DNA damage, but rather delayed recruitment of phosphorylated BRCA1 (S1423) and repair of DSBs. These results highlight that stable epigenetic changes are possible following a single dose of RT and may have significant clinical implications for cancer treatment involving recurrent or fractionated dosing regimens.
Assuntos
Azacitidina/farmacologia , Dano ao DNA , Metilação de DNA , Neoplasias da Próstata/genética , Proteína BRCA1/metabolismo , Linhagem Celular Tumoral , Ilhas de CpG/efeitos dos fármacos , Ilhas de CpG/efeitos da radiação , Metilação de DNA/efeitos dos fármacos , Metilação de DNA/efeitos da radiação , Epigênese Genética/efeitos dos fármacos , Epigênese Genética/efeitos da radiação , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Masculino , Células PC-3 , Fosforilação , Neoplasias da Próstata/tratamento farmacológico , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/radioterapia , Tolerância a Radiação , Análise de Sequência de DNARESUMO
Integrins are transmembrane adhesion receptors that play an important role in hematopoiesis by facilitating interactions between hematopoietic cells and extracellular matrix components of the bone marrow and hematopoietic tissues. These interactions are important in regulating the function, proliferation, and differentiation of hematopoietic cells, as well as their homing and mobilization in the bone marrow. Not surprisingly altered expression and function of integrins plays a key role in the development and progression of cancer including leukemias. However, the regulation of integrin gene expression is not well characterized and the mechanisms by which integrin genes are disrupted in cancer remain unclear. Here we demonstrate for the first time that a key regulator of hematopoiesis, RUNX1, binds to and regulates the promoters of both the ITGA6 and ITGB4 genes in myeloid cells. The ITGA6 and ITGB4 integrin genes form the α6ß4 integrin receptor. However, our data indicate that RUNX1 functions differently at these two promoters. RUNX1 regulates ITGA6 through a consensus RUNX1 binding motif in its promoter. In contrast, although the ITGB4 promoter is also activated by RUNX1, it does so in the absence of a recognized consensus RUNX1 binding motif. Furthermore, our data suggest that regulation of ITGB4 may involve interactions between the promoter and upstream regulatory elements.
Assuntos
Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/genética , Integrina alfa6/metabolismo , Integrina beta4/metabolismo , Células Mieloides/metabolismo , Diferenciação Celular/genética , Embrião de Mamíferos/metabolismo , Hematopoese/genética , Células-Tronco Hematopoéticas/metabolismo , Humanos , Mutação/genética , Regiões Promotoras Genéticas/genéticaRESUMO
Activation of cytokine signaling via the leukemia inhibitory factor receptor (LIFR) plays an integral role in hematopoiesis, osteogenesis, and placental development, along with mediating neurotrophic mechanisms. However, the regulatory control of the LIFR gene has remained largely unexplored. Here, we characterize the LIFR gene as a novel target of the RUNX1 transcription factor. The RUNX1 transcription factor is an essential regulator of hematopoiesis and is a frequent target of point mutations and chromosomal alterations in leukemia. RUNX1 regulates hematopoiesis through its control of genes important for hematopoietic cell growth, proliferation, and differentiation, including a number of cytokines and cytokine receptors. LIFR is regulated by two alternate promoters: a placental-specific and a ubiquitously active general promoter. We show that both of these promoters are regulated by RUNX1. However, in myeloid cells LIFR expression is driven solely by the general LIFR promoter with our data indicating that the placental promoter is epigenetically silenced in these cells. While RUNX1 activates the LIFR general promoter, the oncogenic RUNX1-ETO fusion protein generated by the t(8;21) translocation commonly associated with acute myeloid leukemia represses promoter activity. The data presented here establish LIFR as a transcriptional target of RUNX1 and suggest that disruption of RUNX1 activity in myeloid cells may result in altered LIFR signaling in these cells.
Assuntos
Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Receptores de OSM-LIF/metabolismo , Western Blotting , Diferenciação Celular/genética , Diferenciação Celular/fisiologia , Linhagem Celular Tumoral , Proliferação de Células/genética , Proliferação de Células/fisiologia , Imunoprecipitação da Cromatina , Aberrações Cromossômicas , Subunidade alfa 2 de Fator de Ligação ao Core/genética , Humanos , Células Mieloides/metabolismo , Mutação Puntual/genética , Regiões Promotoras Genéticas/genética , Ligação Proteica/genética , Ligação Proteica/fisiologia , Receptores de Citocinas/genética , Receptores de Citocinas/metabolismo , Receptores de OSM-LIF/genéticaRESUMO
The genome has the ability to respond in a precise and co-ordinated manner to cellular signals. It achieves this through the concerted actions of transcription factors and the chromatin platform, which are targets of the signaling pathways. Our understanding of the molecular mechanisms through which transcription factors and the chromatin landscape each control gene activity has expanded dramatically over recent years, and attention has now turned to understanding the complex, multifaceted interplay between these regulatory layers in normal and disease states. It has become apparent that transcription factors as well as the components and modifiers of the epigenetic machinery are frequent targets of genomic alterations in cancer cells. Through the study of these factors, we can gain unique insight into the dynamic interplay between transcription factors and the epigenome, and how their dysregulation leads to aberrant gene expression programs in cancer. Here, we will highlight how these factors normally co-operate to establish and maintain the transcriptional and epigenetic landscape of cells, and how this is reprogramed in cancer, focusing on the RUNX1 transcription factor and oncogenic derivative RUNX1-ETO in leukemia as paradigms of transcriptional and epigenetic reprograming.
RESUMO
Devil facial tumour disease (DFTD) is a fatally transmissible cancer that threatens the Tasmanian devil population. As Tasmanian devils do not produce an immune response against DFTD cells, an effective vaccine will require a strong adjuvant. Activation of innate immune system cells through toll-like receptors (TLRs) could provide this stimulation. It is unknown whether marsupials, including Tasmanian devils, express functional TLRs. We isolated RNA from peripheral blood mononuclear cells and, with PCR, detected transcripts for TLRs 2, 3, 4, 5, 6, 7, 8, 9, 10 and 13. Stimulation of the mononuclear cells with agonists to these TLRs increased the expression of downstream TLR signaling products (IL1α, IL6, IL12A and IFNß). Our data provide the first evidence that TLR signaling is functional in the mononuclear cells of the Tasmanian devil. Future DFTD vaccination trials will incorporate TLR agonists to enhance the immune response against DFTD.
Assuntos
Neoplasias Faciais/imunologia , Imunidade Inata/imunologia , Leucócitos Mononucleares/imunologia , Marsupiais/imunologia , Receptores Toll-Like/imunologia , Animais , Neoplasias Faciais/prevenção & controle , Interferon beta/biossíntese , Interferon beta/imunologia , Subunidade p35 da Interleucina-12/biossíntese , Subunidade p35 da Interleucina-12/imunologia , Interleucina-1alfa/biossíntese , Interleucina-1alfa/imunologia , Interleucina-6/biossíntese , Interleucina-6/imunologia , Transdução de Sinais/imunologia , Receptores Toll-Like/agonistasRESUMO
BACKGROUND: Radiotherapy is a chosen treatment option for prostate cancer patients and while some tumours respond well, up to 50% of patients may experience tumour recurrence. Identification of functionally relevant predictive biomarkers for radioresponse in prostate cancer would enable radioresistant patients to be directed to more appropriate treatment options, avoiding the side-effects of radiotherapy. METHODS: Using an in vitro model to screen for novel biomarkers of radioresistance, transcriptome analysis of a radioresistant (PC-3) and radiosensitive (LNCaP) prostate cancer cell line was performed. Following pathway analysis candidate genes were validated using qRT-PCR. The DNA repair pathway in radioresistant PC-3 cells was then targeted for radiation sensitization using the PARP inhibitor, niacinimide. RESULTS: Opposing regulation of a DNA repair and replication pathway was observed between PC-3 and LNCaP cells from RNA-seq analysis. Candidate genes BRCA1, RAD51, FANCG, MCM7, CDC6 and ORC1 were identified as being significantly differentially regulated post-irradiation. qRT-PCR validation confirmed BRCA1, RAD51 and FANCG as being significantly differentially regulated at 24 hours post radiotherapy (p-value =0.003, 0.045 and 0.003 respectively). While the radiosensitive LNCaP cells down-regulated BRCA1, FANCG and RAD51, the radioresistant PC-3 cell line up-regulated these candidates to promote cell survival post-radiotherapy and a similar trend was observed for MCM7, CDC6 and ORC1. Inhibition of DNA repair using niacinamide sensitised the radioresistant cells to irradiation, reducing cell survival at 2 Gy from 66% to 44.3% (p-value =0.02). CONCLUSIONS: These findings suggest that the DNA repair candidates identified via RNA-seq hold potential as both targets for radiation sensitization and predictive biomarkers in prostate cancer.
Assuntos
Biomarcadores Tumorais/genética , Reparo do DNA/efeitos da radiação , Regulação Neoplásica da Expressão Gênica/efeitos da radiação , Neoplasias da Próstata/genética , Neoplasias da Próstata/radioterapia , Tolerância a Radiação/genética , Proteína BRCA1/genética , Proteína BRCA1/metabolismo , Proteínas de Ciclo Celular/genética , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos da radiação , Reparo do DNA/efeitos dos fármacos , Regulação para Baixo/efeitos da radiação , Inibidores Enzimáticos/farmacologia , Proteína do Grupo de Complementação G da Anemia de Fanconi/genética , Perfilação da Expressão Gênica , Humanos , Masculino , Componente 7 do Complexo de Manutenção de Minicromossomo/genética , Niacinamida/farmacologia , Proteínas Nucleares/genética , Complexo de Reconhecimento de Origem/genética , Inibidores de Poli(ADP-Ribose) Polimerases , RNA Mensageiro/análise , Rad51 Recombinase/genética , Rad51 Recombinase/metabolismo , Radiossensibilizantes/uso terapêutico , Regulação para Cima/efeitos da radiaçãoRESUMO
The role of the Nuclear Factor κB (NF-κB) transcription factor family in T cell function has been well described. The c-Rel family member is of particular importance in initiating T cell responses to antigen and regulating activation of inflammatory cytokine genes, including the Interleukin-2 (IL-2) and Granulocyte macrophage colony stimulating factor (GM-CSF) genes. c-Rel is required for chromatin remodeling of these gene promoters, which involves depletion of histones from the promoters in response to T cell activating signals. These chromatin remodeling events precede transcriptional activation of the genes. The subsequent down-regulation of cytokine gene expression is important in the termination of an immune response and here we examine this process at the murine GM-CSF and IL-2 genes. We show that the cytokine mRNA levels rapidly return to basal levels following stimulus removal and this is associated with reassembly of histones onto the promoter. Histone reassembly at the GM-CSF and IL-2 promoters occurs concomitantly with depletion of RelA, c-Rel and RNA polymerase II from the promoters. Furthermore we show that transcriptional down-regulation and chromatin reassembly is dependent on depletion of c-Rel from the nucleus, and that this is regulated by the nuclear translocation of the NF-κB inhibitor, IκBα. The nuclear activation of c-Rel therefore not only regulates the initiation of GM-CSF and IL-2 gene activation in response to T cell activation, but also the termination of these gene responses following the removal of the activating signal.
Assuntos
Montagem e Desmontagem da Cromatina , Fator Estimulador de Colônias de Granulócitos e Macrófagos/genética , Interleucina-2/genética , Ativação Linfocitária , Proteínas Proto-Oncogênicas c-rel/metabolismo , Linfócitos T/metabolismo , Animais , Linhagem Celular , Núcleo Celular/metabolismo , Regulação para Baixo , Fator Estimulador de Colônias de Granulócitos e Macrófagos/metabolismo , Histonas/metabolismo , Proteínas I-kappa B/metabolismo , Interleucina-2/metabolismo , Camundongos , Inibidor de NF-kappaB alfa , Regiões Promotoras Genéticas , Ligação Proteica , Transporte Proteico , Proteólise , Proteínas Proto-Oncogênicas c-rel/fisiologia , RNA Polimerase II/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Linfócitos T/imunologia , Transcrição GênicaRESUMO
PURPOSE: Patients presenting with locally advanced rectal cancer currently receive preoperative radiotherapy with or without chemotherapy. Although pathologic complete response is achieved for approximately 10% to 30% of patients, a proportion of patients derive no benefit from this therapy while being exposed to toxic side effects of treatment. Therefore, there is a strong need to identify patients who are unlikely to benefit from neoadjuvant therapy to help direct them toward alternate and ultimately more successful treatment options. EXPERIMENTAL DESIGN: In this study, we obtained expression profiles from pretreatment biopsies for 51 rectal cancer patients. All patients underwent preoperative chemoradiotherapy, followed by resection of the tumor 6 to 8 weeks posttreatment. Gene expression and response to treatment were correlated, and a supervised learning algorithm was used to generate an original predictive classifier and validate previously published classifiers. RESULTS: Novel predictive classifiers based on Mandard's tumor regression grade, metabolic response, TNM (tumor node metastasis) downstaging, and normal tissue expression profiles were generated. Because there were only 7 patients who had minimal treatment response (>80% residual tumor), expression profiles were used to predict good tumor response and outcome. These classifiers peaked at 82% sensitivity and 89% specificity; however, classifiers with the highest sensitivity had poor specificity, and vice versa. Validation of predictive classifiers from previously published reports was attempted using this cohort; however, sensitivity and specificity ranged from 21% to 70%. CONCLUSIONS: These results show that the clinical utility of microarrays in predictive medicine is not yet within reach for rectal cancer and alternatives to microarrays should be considered for predictive studies in rectal adenocarcinoma.
Assuntos
Adenocarcinoma/tratamento farmacológico , Adenocarcinoma/radioterapia , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Biomarcadores Tumorais/genética , Perfilação da Expressão Gênica , Neoplasias Retais/tratamento farmacológico , Neoplasias Retais/radioterapia , Adenocarcinoma/diagnóstico , Adenocarcinoma/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Biomarcadores Farmacológicos/análise , Biomarcadores Farmacológicos/metabolismo , Biomarcadores Tumorais/análise , Biomarcadores Tumorais/metabolismo , Terapia Combinada , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Masculino , Análise em Microsséries , Pessoa de Meia-Idade , Terapia Neoadjuvante , Prognóstico , Neoplasias Retais/diagnóstico , Neoplasias Retais/genética , Fatores de TempoRESUMO
Cancer treatment is now moving toward a personalized approach, promising improved rates of response and survival. A number of studies have employed the use of microarrays to investigate the predictive potential of expression profiling in gastrointestinal (GI) cancer patients. However while many robust predictive classifiers relating to response and prognosis have been generated for GI cancer patients, these have yet to make the transition to the clinic. The main obstacle is the limited cross validation between predictive gene lists identified for the same tumor type and outcome. Differences in the experimental design, analysis, and interpretation of results all contribute to this variation, with numerous factors influencing which genes are highlighted as predictive. While predictive genomics shows immense potential, it is still a relatively new field and the validation of predictive gene lists derived from microarray data remains a challenge. Future studies must carefully consider all aspects of experimental design to ensure a clinically applicable predictive test can be developed. With this in mind, more extensive and collaborative research must be undertaken before microarray-based platforms can be used routinely in tailoring GI cancer treatment and change clinical practice. Larger cohorts and consistency in methodology will enable the findings from this research to make the transition to the clinic.
Assuntos
Biomarcadores Tumorais/genética , Neoplasias Gastrointestinais/genética , Perfilação da Expressão Gênica , Neoplasias Gastrointestinais/diagnóstico , Neoplasias Gastrointestinais/terapia , Humanos , Análise de Sequência com Séries de Oligonucleotídeos , PrognósticoRESUMO
Granulocyte-macrophage colony stimulating factor (GM-CSF) plays a key role in myeloid cell function and is rapidly and transiently expressed in T cells in response to immune or inflammatory stimuli. Induction of GM-CSF gene expression is accompanied by changes in chromatin structure across the proximal promoter region of the gene. We show that the promoter remodelling and subsequent gene transcription occurs with distinct signal and transcription factor requirements. Activation of the protein kinase C (PKC) signalling pathway is sufficient to induce changes in chromatin structure across the promoter, but both the PKC and calcium signalling pathways are required for efficient gene transcription. Although NFAT transcription factors contribute to GM-CSF gene transcription, they are not required for promoter remodelling. However, the presence of the nuclear factor-kappaB transcription factor, c-Rel, in the nucleus is strongly correlated with and required for the events of chromatin remodelling.