RESUMEN
Radiotherapy (RT) is commonly used to try to eliminate any remaining tumor cells following surgical resection of glioma. However, tumor recurrence is prevalent, highlighting the unmet medical need to develop therapeutic strategies to enhance the efficacy of RT in glioma. Focusing on the radiosensitizing potential of currently approved drugs known to cross the blood-brain barrier can facilitate rapid clinical translation. Here, we assessed the role of catechol-o-methyltransferase (COMT), a key enzyme to degrade catecholamines and a drug target for Parkinson's disease, in glioma treatment. Analysis of TCGA data showed significantly higher COMT expression levels in both low-grade glioma and glioblastoma compared to normal brain tissues. Inhibition of COMT by genetic knockout or FDA-approved COMT inhibitors significantly sensitized glioma cells to RT in vitro and in vivo. Mechanistically, COMT inhibition in glioma cells led to mitochondria dysfunction and increased mitochondrial RNA release into the cytoplasm, activating the cellular antiviral double-stranded RNA sensing pathway and type I interferon (IFN) response. Elevated type I IFNs stimulated the phagocytic capacity of microglial cells, enhancing RT efficacy. Given the long-established safety record of the COMT inhibitors, these findings provide a solid rationale to evaluate them in combination with RT in glioma patients.
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Accumulating evidence suggests that caspase-3 plays critical roles beyond apoptosis, serving pro-survival functions in malignant transformation and tumorigenesis. However, the mechanism of non-apoptotic action of caspase-3 in oncogenic transformation remains unclear. In the present study, we show that caspase-3 is consistently activated in malignant transformation induced by exogenous expression of oncogenic cocktail (c-Myc, p53DD, Oct-4, and H-Ras) in vitro as well as in the mouse mammary tumor virus-polyomavirus middle T antigen (MMTV-PyMT) mouse model of breast cancer. Genetic ablation of caspase-3 significantly attenuated oncogene-induced transformation of mammalian cells and delayed breast cancer progression in MMTV-PyMT transgenic mice. Mechanistically, active caspase-3 triggers the translocation of endonuclease G (EndoG) from mitochondria, which migrates to the nucleus, thereby induces phosphorylation of Src-STAT3 signaling pathway to facilitate oncogenic transformation. Taken together, our data suggest that caspase-3 plays pivotal role in facilitating rather than suppressing oncogene-induced malignant transformation of mammalian cells.
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Caspasa 3 , Transformación Celular Neoplásica , Oncogenes , Factor de Transcripción STAT3 , Animales , Femenino , Humanos , Ratones , Caspasa 3/metabolismo , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/metabolismo , Ratones Transgénicos , Mitocondrias/metabolismo , Oncogenes/genética , Fosforilación , Transducción de Señal , Familia-src Quinasas/metabolismo , Familia-src Quinasas/genética , Factor de Transcripción STAT3/metabolismoRESUMEN
von Hippel-Lindau (VHL), known as a tumor suppressor gene, is frequently mutated in clear cell renal cell carcinoma (ccRCC). However, VHL mutation is not sufficient to promote tumor formation. In most cases other than ccRCC, VHL loss alters cellular homeostasis and causes cell stress and metabolic changes by stabilizing hypoxia-inducible factor (HIF) levels, resulting in a fitness disadvantage. In addition, the function of VHL in regulating immune response is still not well established. In this study, we demonstrate that VHL loss enhances the efficacy of anti-programmed death 1 (PD1) treatment in multiple murine tumor models in a T cell-dependent manner. Mechanistically, we discovered that upregulation of HIF1α/2α induced by VHL loss decreased mitochondrial outer membrane potential and caused the cytoplasmic leakage of mitochondrial DNA, which triggered cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) activation and induced type I interferons. Our study thus provided mechanistic insights into the role of VHL gene loss in boosting antitumor immunity.
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Despite a moderate mutation burden, clear cell renal cell carcinoma (ccRCC) responds well to immune checkpoint blockade (ICB) therapy. Here we report that loss-of-function mutations in the von Hippel-Lindau (VHL) gene, the most frequent in ccRCC, underlies its responsiveness to ICB therapy. We demonstrate that genetic knockout of the VHL gene enhanced the efficacy of anti-PD-1 therapy in multiple murine tumor models in a T cell-dependent manner. Mechanistically, we discovered that upregulation of HIF1α and HIF2α induced by VHL gene loss decreased mitochondrial outer membrane potential and caused the cytoplasmic leakage of mitochondrial DNA (mtDNA), which triggered cGAS-STING activation and induced type I interferons. Our study thus provided novel mechanistic insights into the role of VHL gene loss in potentiating ccRCC immunotherapy.
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Cytotoxic chemotherapy is a primary treatment modality for many patients with advanced cancer. Increasing preclinical and clinical observations indicate that chemotherapy can exacerbate tumor metastasis. However, the underlying mechanism remains unclear. Here, it is attempted to identify the mechanisms underlying chemotherapy-induced cancer recurrence and metastasis. It is revealed that a small subpopulation of "near-death cells" (NDCs) with compromised plasma membranes can reverse the death process to enhance survival and repopulation after exposure to lethal doses of cytotoxins. Moreover, these NDCs acquire enhanced tumorigenic and metastatic capabilities, but maintain chemosensitivity in multiple models. Mechanistically, cytotoxin exposure induces activating transcription factor 4 (ATF4)-dependent nonclassical NF-κB signaling activation; ultimately, this results in nuclear translocation of p52 and RelB in NDCs. Deletion of ATF4 in parental cancer cells significantly reduces colony formation and metastasis of NDCs, whereas overexpression of ATF4 activates the nonclassical NF-κB signaling pathway to promote chemotherapy-induced metastasis of NDCs. Overall, these results provide novel mechanistic insights into the chemotherapy-induced metastasis and indicate the pivotal role of NDCs in mediating tumor relapse after cytotoxic therapy. This study also suggests that targeting ATF4 may be an effective approach in improving the efficacy of chemotherapy.
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Antineoplásicos , FN-kappa B , Humanos , FN-kappa B/metabolismo , Factor de Transcripción Activador 4/metabolismo , Recurrencia Local de Neoplasia , Transducción de SeñalRESUMEN
PURPOSE: To provide an updated summary of recent advances in our understanding of the non-canonical roles of apoptotic and DNA double-strand break repair factors in various biological processes, especially in the cellular response to radiotherapy. CONCLUSION: Apoptotic caspases are usually considered as "executioners'' of unwanted or damaged cells or tissues. However, recent studies indicated they play multiple additional, often counterintuitive roles in many biological processes. Similarly, DNA double-strand break (DSB) repair factors were also found to play unexpected roles beyond repairing damaged DNA. In this review, I will summarize key findings on the non-canonical roles of apoptotic and DSB repair factors in disparate biological and pathological processes such as radiation-induced genetic instability and carcinogenesis, wound healing and tissue regeneration, induced pluripotent stem cell induction, spontaneous and stochastic generation of cancer stem cells, and cancer immunotherapy. I believe these findings will usher in more studies in this exciting and rapidly evolving field.
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Roturas del ADN de Doble Cadena , Reparación del ADN , Daño del ADN , ADN , Radiación IonizanteRESUMEN
The type I interferon response plays a pivotal role in promoting antitumor immune activity in response to radiotherapy. The identification of approaches to boost the radiation-induced type I interferon response could help improve the efficacy of radiotherapy. Here we show that the histone methyltransferase SETDB1 is a potent suppressor of radiation-induced endogenous retrovirus expression. SETDB1 inhibition significantly enhanced the efficacy of radiotherapy by promoting radiation-induced viral mimicry to upregulate type I interferons. SETDB1 expression correlated with radiotherapy efficacy in human non-small cell carcinoma and melanoma patients. In a murine tumor model, genetic deletion of Setdb1 significantly enhanced radiotherapy efficacy, and Setdb1-deficient tumors had enhanced intratumoral lymphocyte infiltration, an observation confirmed in human cancer samples. Setdb1 deficiency led to increased basal and radiation-induced endogenous retrovirus (ERV) expression, enhanced MDA5/MAVS signaling, and upregulated type I interferons, which were essential for SETDB1 deficiency-induced radiosensitization. Taken together, these data suggest that inhibition of SETDB1 is a promising approach to enhance cancer radiotherapy efficacy by promoting radiation-induced viral mimicry and antitumor immunity through ERV induction. SIGNIFICANCE: The identification of the SETDB1-mediated suppression of radiotherapy-induced viral mimicry reveals SETDB1 inhibition as a potential approach to sensitize tumors to radiotherapy by enhancing the type I interferon response.
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Retrovirus Endógenos , N-Metiltransferasa de Histona-Lisina , Interferón Tipo I , Melanoma , Animales , Retrovirus Endógenos/genética , N-Metiltransferasa de Histona-Lisina/genética , Humanos , Interferón Tipo I/inmunología , Melanoma/genética , Melanoma/inmunología , Melanoma/radioterapia , Ratones , Transducción de SeñalRESUMEN
Immune checkpoint blockade therapy has drastically improved the prognosis of certain advanced-stage cancers. However, low response rates and immune-related adverse events remain important limitations. Here, we report that inhibiting ALG3, an a-1,3-mannosyltransferase involved in protein glycosylation in the endoplasmic reticulum (ER), can boost the response of tumors to immune checkpoint blockade therapy. Deleting N-linked glycosylation gene ALG3 in mouse cancer cells substantially attenuates their growth in mice in a manner depending on cytotoxic T cells. Furthermore, ALG3 inhibition or N-linked glycosylation inhibitor tunicamycin treatment synergizes with anti-PD1 therapy in suppressing tumor growth in mouse models of cancer. Mechanistically, we found that inhibiting ALG3 induced deficiencies of post-translational N-linked glycosylation modification and led to excessive lipid accumulation through sterol-regulated element-binding protein (SREBP1)-dependent lipogenesis in cancer cells. N-linked glycosylation deficiency-mediated lipid hyperperoxidation induced immunogenic ferroptosis of cancer cells and promoted a pro-inflammatory microenvironment, which boosted anti-tumor immune responses. In human subjects with cancer, elevated levels of ALG3 expression in tumor tissues are associated with poor patient survival. Taken together, we reveal an unappreciated role of ALG3 in regulating tumor immunogenicity and propose a potential therapeutic strategy for enhancing cancer immunotherapy.
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Ferroptosis , Manosiltransferasas , Neoplasias , Animales , Humanos , Inhibidores de Puntos de Control Inmunológico , Inmunoterapia , Lípidos , Manosiltransferasas/genética , Manosiltransferasas/metabolismo , Ratones , Neoplasias/terapiaRESUMEN
Alloreactive donor T cells undergo extensive metabolic reprogramming to become activated and induce graft-versus-host disease (GVHD) upon alloantigen encounter. It is generally thought that glycolysis, which promotes T cell growth and clonal expansion, is employed in this process. However, conflicting data have been reported regarding the requirement of glycolysis to induce T cell-mediated GVHD due to the lack of T cell-specific treatments using glycolysis inhibitors. Importantly, previous studies have not evaluated whether graft-versus-leukemia (GVL) activity is preserved in donor T cells deficient for glycolysis. As a critical component affecting the clinical outcome, it is necessary to assess the anti-tumor activity following treatment with metabolic modulators in preclinical models. In the present study, we utilized T cells selectively deficient for glucose transporter 1 (Glut1T-KO), to examine the role of glycolysis exclusively in alloreactive T cells without off-targeting effects from antigen presenting cells and other cell types that are dependent on glycolysis. We demonstrated that transfer of Glut1T-KO T cells significantly improved acute GVHD outcomes through increased apoptotic rates, impaired expansion, and decreased proinflammatory cytokine production. In addition to impaired GVHD development, donor Glut1T-KO T cells mediated sufficient GVL activity to protect recipients from tumor development. A clinically relevant approach using donor T cells treated with a small molecule inhibitor of glycolysis, 2-Deoxy-D-glucose ex vivo, further demonstrated protection from tumor development. These findings indicate that treatment with glycolysis inhibitors prior to transplantation selectively eliminates alloreactive T cells, but spares non-alloreactive T cells including those that protect against tumor growth. The present study has established a definitive role for glycolysis in acute GVHD and demonstrated that acute GVHD can be selectively prevented through targeting glycolysis.
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Enfermedad Injerto contra Huésped , Trasplante de Células Madre Hematopoyéticas , Leucemia , Transportador de Glucosa de Tipo 1/genética , Transportador de Glucosa de Tipo 1/metabolismo , Glucólisis , Humanos , Linfocitos TRESUMEN
Objective: SET8 is a member of the SET domain-containing family and the only known lysine methyltransferase (KMT) that monomethylates lysine 20 of histone H4 (H4K20me1). SET8 has been implicated in many essential cellular processes, including cell cycle regulation, DNA replication, DNA damage response, and carcinogenesis. There is no conclusive evidence, however, regarding the effect of SET8 on radiotherapy. In the current study we determined the efficacy of SET8 inhibition on radiotherapy of tumors and the underlying mechanism. Methods: First, we explored the radiotherapy benefit of the SET8 expression signature by analyzing clinical data. Then, we measured a series of biological endpoints, including the xenograft tumor growth in mice and apoptosis, frequency of micronuclei, and foci of 53BP1 and γ-H2AX in cells to detect the SET8 effects on radiosensitivity. RNA sequencing and subsequent experiments were exploited to verify the mechanism underlying the SET8 effects on radiotherapy. Results: Low expression of SET8 predicted a better benefit to radiotherapy in lung adenocarcinoma (LUAD) and invasive breast carcinoma (BRCA) patients. Furthermore, genetic deletion of SET8 significantly enhanced radiation treatment efficacy in a murine tumor model, and A549 and MCF7 cells; SET8 overexpression decreased the radiosensitivity. SET8 inhibition induced more apoptosis, the frequency of micronuclei, and blocked the kinetics process of DNA damage repair as 53BP1 and γ-H2AX foci remained in cells. Moreover, RNF8 was positively correlated with the SET8 impact on DNA damage repair. Conclusion: Our results demonstrated that SET8 inhibition enhanced radiosensitivity by suppressing DNA damage repair, thus suggesting that SET8 potentiated radiotherapy of carcinomas. As new inhibitors of SET8 are synthesized and tested in preclinical and clinical settings, combining SET8 inhibitors with radiation warrants consideration for precise radiotherapy.
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Carcinogénesis , Carcinoma , Daño del ADN , Replicación del ADN , Radioterapia , Animales , Apoptosis , Carcinoma/genética , Carcinoma/radioterapia , Ciclo Celular , Línea Celular Tumoral , Células HeLa , N-Metiltransferasa de Histona-Lisina , Humanos , RatonesRESUMEN
ATM (ataxia-telangiectasia mutated) is an important cell-cycle checkpoint kinase required for cellular response to DNA damage. Activated by DNA double strand breaks, ATM regulates the activities of many downstream proteins involved in various carcinogenic events. Therefore, ATM or its genetic variants may have a pleiotropic effect on cancer development. We conducted a pleiotropic analysis to evaluate associations between genetic variants of ATM and risk of multiple cancers. With genotyping data extracted from previously published genome-wide association studies of various cancers, we performed multivariate logistic regression analysis, followed by a meta-analysis for each cancer site, to identify cancer risk-associated single-nucleotide polymorphisms (SNPs). In the ASSET two-sided analysis, we found that two ATM SNPs were significantly associated with risk of multiple cancers. One tagging SNP (rs1800057 C>G) was associated with risk of multiple cancers (two-sided P = 5.27 × 10-7). Because ATM rs1800057 is a missense variant, we also explored the intermediate phenotypes through which this variant may confer risk of multiple cancers and identified a possible immune-mediated effect of this variant. Our findings indicate that genetic variants of ATM may have a pleiotropic effect on cancer risk and thus provide an important insight into common mechanisms of carcinogenesis.
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Proteínas de la Ataxia Telangiectasia Mutada/genética , Predisposición Genética a la Enfermedad/genética , Neoplasias/genética , Polimorfismo de Nucleótido Simple/genética , Roturas del ADN de Doble Cadena , Daño del ADN/genética , Humanos , FenotipoRESUMEN
INTRODUCTION: Identification of patients who can benefit from immune checkpoint blockade (ICB) therapy is key for improved clinical outcome. Recently, U.S. Food and Drug Administration approved tumor mutational burden (TMB) high (TMB-H or TMB ≥ 10) as a biomarker for pembrolizumab treatment of solid tumors. We intend to test the hypothesis that mutations in select genes may be a better predictor of NSCLC response to ICB therapy than TMB-H. METHODS: We compiled a list of candidate genes that may predict for benefits from ICB treatment by use of data from a recently published cohort of 350 patients with NSCLC. We then evaluated the influences of different mutation signatures in the candidate genes on ICB efficacy. They were also compared with TMB-H. The predictive powers of different mutation signatures were then evaluated in an independent cohort of patients with NSCLC treated with ICB. RESULTS: A compound mutation signature, in which two or more of the 52 candidate genes were mutated, accounted for 145 of 350 patients with NSCLC and was associated with considerable ICB treatment benefits. Specifically, the median duration of overall survival was 36 versus 8 months in NSCLC in those with two or more versus none of the 52 genes mutated. Moreover, those patients with the compound mutation signature but had low TMB (<10) achieved significant overall survival benefits when compared with those without the signature but had TMB-H (≥10). Finally, in an independent cohort of 156 patients with ICB-treated NSCLC, the median duration of progression-free survival was 8.3 months versus 3.5 months in those with the compound mutation signature versus those with none mutated in the 52 genes. CONCLUSIONS: A genetic signature with mutations in at least two of 52 candidate genes was superior than TMB-H in predicting clinical benefits for ICB therapy in patients with NSCLC.
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Carcinoma de Pulmón de Células no Pequeñas , Neoplasias Pulmonares , Biomarcadores de Tumor/genética , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Carcinoma de Pulmón de Células no Pequeñas/genética , Humanos , Inmunoterapia , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/genética , MutaciónRESUMEN
Novel approaches are needed to boost the efficacy of immune checkpoint blockade (ICB) therapy. Ataxia telangiectasia mutated (ATM) protein plays a central role in sensing DNA double-stranded breaks (DSBs) and coordinating their repair. Recent data indicated that ATM might be a promising target to enhance ICB therapy. However, the molecular mechanism involved has not been clearly elucidated. Here, we show that ATM inhibition could potentiate ICB therapy by promoting cytoplasmic leakage of mitochondrial DNA (mtDNA) and activation of the cGAS/STING pathway. We show that genetic depletion of ATM in murine cancer cells delayed tumor growth in syngeneic mouse hosts in a T cell-dependent manner. Furthermore, chemical inhibition of ATM potentiated anti-PD-1 therapy of mouse tumors. ATM inhibition potently activated the cGAS/STING pathway and enhanced lymphocyte infiltration into the tumor microenvironment by downregulating mitochondrial transcription factor A (TFAM), which led to mtDNA leakage into the cytoplasm. Moreover, our analysis of data from a large patient cohort indicated that ATM mutations, especially nonsense mutations, predicted for clinical benefits of ICB therapy. Our study therefore provides strong evidence that ATM may serve as both a therapeutic target and a biomarker to enable ICB therapy.
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ADN Mitocondrial , Inhibidores de Puntos de Control Inmunológico/farmacología , Inmunoterapia , Proteínas de la Membrana , Proteínas de Neoplasias , Neoplasias Experimentales , Nucleotidiltransferasas , Transducción de Señal , Animales , Proteínas de la Ataxia Telangiectasia Mutada/antagonistas & inhibidores , Proteínas de la Ataxia Telangiectasia Mutada/genética , Proteínas de la Ataxia Telangiectasia Mutada/inmunología , Línea Celular Tumoral , Codón sin Sentido , ADN Mitocondrial/genética , ADN Mitocondrial/inmunología , Humanos , Proteínas de la Membrana/genética , Proteínas de la Membrana/inmunología , Ratones , Proteínas de Neoplasias/antagonistas & inhibidores , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/inmunología , Neoplasias Experimentales/genética , Neoplasias Experimentales/inmunología , Neoplasias Experimentales/terapia , Nucleotidiltransferasas/genética , Nucleotidiltransferasas/inmunología , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Transducción de Señal/inmunologíaRESUMEN
Despite its success in achieving the long-term survival of 10-30% of treated individuals, immune therapy is still ineffective for most patients with cancer1,2. Many efforts are therefore underway to identify new approaches that enhance such immune 'checkpoint' therapy3-5 (so called because its aim is to block proteins that inhibit checkpoint signalling pathways in T cells, thereby freeing those immune cells to target cancer cells). Here we show that inhibiting PCSK9-a key protein in the regulation of cholesterol metabolism6-8-can boost the response of tumours to immune checkpoint therapy, through a mechanism that is independent of PCSK9's cholesterol-regulating functions. Deleting the PCSK9 gene in mouse cancer cells substantially attenuates or prevents their growth in mice in a manner that depends on cytotoxic T cells. It also enhances the efficacy of immune therapy that is targeted at the checkpoint protein PD1. Furthermore, clinically approved PCSK9-neutralizing antibodies synergize with anti-PD1 therapy in suppressing tumour growth in mouse models of cancer. Inhibiting PCSK9-either through genetic deletion or using PCSK9 antibodies-increases the expression of major histocompatibility protein class I (MHC I) proteins on the tumour cell surface, promoting robust intratumoral infiltration of cytotoxic T cells. Mechanistically, we find that PCSK9 can disrupt the recycling of MHC I to the cell surface by associating with it physically and promoting its relocation and degradation in the lysosome. Together, these results suggest that inhibiting PCSK9 is a promising way to enhance immune checkpoint therapy for cancer.
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Inhibidores de Puntos de Control Inmunológico/farmacología , Inhibidores de Puntos de Control Inmunológico/uso terapéutico , Inmunoterapia/métodos , Neoplasias/tratamiento farmacológico , Neoplasias/inmunología , Inhibidores de PCSK9 , Receptor de Muerte Celular Programada 1/antagonistas & inhibidores , Animales , Anticuerpos Neutralizantes/inmunología , Anticuerpos Neutralizantes/farmacología , Anticuerpos Neutralizantes/uso terapéutico , Línea Celular Tumoral , Modelos Animales de Enfermedad , Femenino , Antígenos de Histocompatibilidad Clase I/inmunología , Antígenos de Histocompatibilidad Clase I/metabolismo , Humanos , Lisosomas/metabolismo , Ratones , Neoplasias/metabolismo , Neoplasias/patología , Proproteína Convertasa 9/deficiencia , Proproteína Convertasa 9/genética , Proproteína Convertasa 9/inmunología , Linfocitos T Citotóxicos/citología , Linfocitos T Citotóxicos/inmunología , Ensayos Antitumor por Modelo de XenoinjertoAsunto(s)
Infecciones por Coronavirus/terapia , Citocinas/biosíntesis , Glicina/metabolismo , Neumonía Viral/terapia , Betacoronavirus/efectos de los fármacos , Betacoronavirus/patogenicidad , Vasos Sanguíneos/inmunología , Vasos Sanguíneos/virología , Encéfalo/inmunología , Encéfalo/virología , COVID-19 , Infecciones por Coronavirus/genética , Infecciones por Coronavirus/metabolismo , Infecciones por Coronavirus/virología , Citocinas/efectos de los fármacos , Citocinas/genética , Glicina/genética , Glicina/uso terapéutico , Corazón/virología , Humanos , Intestinos/inmunología , Intestinos/virología , Riñón/inmunología , Riñón/virología , Hígado/inmunología , Hígado/virología , Pulmón/inmunología , Pulmón/virología , Pandemias , Neumonía Viral/genética , Neumonía Viral/metabolismo , Neumonía Viral/virología , SARS-CoV-2RESUMEN
More than 30% of genes in higher eukaryotes are regulated by RNA polymerase II (Pol II) promoter proximal pausing. Pausing is released by the positive transcription elongation factor complex (P-TEFb). However, the exact mechanism by which this occurs and whether phosphorylation of the carboxyl-terminal domain of Pol II is involved in the process remains unknown. We previously reported that JMJD5 could generate tailless nucleosomes at position +1 from transcription start sites (TSS), thus perhaps enable progression of Pol II. Here we find that knockout of JMJD5 leads to accumulation of nucleosomes at position +1. Absence of JMJD5 also results in loss of or lowered transcription of a large number of genes. Interestingly, we found that phosphorylation, by CDK9, of Ser2 within two neighboring heptad repeats in the carboxyl-terminal domain of Pol II, together with phosphorylation of Ser5 within the second repeat, HR-Ser2p (1, 2)-Ser5p (2) for short, allows Pol II to bind JMJD5 via engagement of the N-terminal domain of JMJD5. We suggest that these events bring JMJD5 near the nucleosome at position +1, thus allowing JMJD5 to clip histones on this nucleosome, a phenomenon that may contribute to release of Pol II pausing.
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Quinasa 9 Dependiente de la Ciclina/metabolismo , Histona Demetilasas/metabolismo , ARN Polimerasa II/metabolismo , Transcripción Genética , Línea Celular Tumoral , Quinasa 9 Dependiente de la Ciclina/genética , Histona Demetilasas/química , Histona Demetilasas/genética , Humanos , Nucleosomas/genética , Nucleosomas/metabolismo , Fosforilación , Factor B de Elongación Transcripcional Positiva/genética , Factor B de Elongación Transcripcional Positiva/metabolismo , Regiones Promotoras Genéticas , Unión Proteica , Dominios Proteicos , ARN Polimerasa II/genéticaRESUMEN
Limited mitochondria outer membrane permeability (MOMP) is a novel biological process where mammalian cells initiate the intrinsic apoptosis pathway with increased mitochondrial permeability but survive. One of the major consequences of limited MOMP is apoptotic endonuclease-induced DNA double strand breaks. Recent studies indicate that these DNA double stand breaks and ensuing activation of DNA damage response factors such as ATM play important but previously underappreciated roles in carcinogenesis and tumor growth. Furthermore, novel non-canonical roles of DNA repair factors such as ATM in tumor growth and treatment are also emerging. In this review, we try to summarize recent findings on this newly revealed link between DNA double strand break repair and cell death pathways.
RESUMEN
The role of the ataxia-telangiectasia-mutated (ATM) gene in human malignancies, especially in solid tumors, remains poorly understood. In the present study, we explored the involvement of ATM in transforming primary human cells into cancer stem cells. We show that ATM plays an unexpected role in facilitating oncogene-induced malignant transformation through transcriptional reprogramming. Exogenous expression of an oncogene cocktail induced a significant amount of DNA double-strand breaks in human fibroblasts that caused persistent activation of ATM, which in turn enabled global transcriptional reprogramming through chromatin relaxation, allowing oncogenic transcription factors to access chromatin. Consistently, deficiencies in ATM significantly attenuated oncogene-induced transformation of human cells. In addition, ATM inhibition significantly reduced tumorigenesis in a mouse model of mammary cancer. ATM and cellular DNA damage response therefore play a previously unknown role in facilitating rather than suppressing oncogene-induced malignant transformation of mammalian cells. SIGNIFICANCE: These findings uncover a novel pro-oncogenic role for ATM and show that contrary to established theory, ATM does not always function as a tumor suppressor; its function is however dependent on cell type.
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Proteínas de la Ataxia Telangiectasia Mutada/genética , Transformación Celular Neoplásica/genética , Reprogramación Celular/genética , Roturas del ADN de Doble Cadena , Reparación del ADN/fisiología , Células Madre Neoplásicas/patología , Animales , Proteínas de la Ataxia Telangiectasia Mutada/antagonistas & inhibidores , Proteínas de la Ataxia Telangiectasia Mutada/deficiencia , Proteínas de la Ataxia Telangiectasia Mutada/metabolismo , Línea Celular , Transformación Celular Neoplásica/patología , Cromatina/genética , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas , Femenino , Fibroblastos/patología , Técnicas de Inactivación de Genes , Marcación de Gen/métodos , Genes p53 , Humanos , Neoplasias Mamarias Animales/genética , Neoplasias Mamarias Animales/patología , Ratones , Ratones Desnudos , Proteínas de Neoplasias/antagonistas & inhibidores , Proteínas de Neoplasias/deficiencia , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , ARN Mensajero/metabolismo , Activación Transcripcional , Transcriptoma/fisiología , Proteína 28 que Contiene Motivos Tripartito/genética , Proteína 28 que Contiene Motivos Tripartito/metabolismo , Ensayo de Tumor de Célula Madre/métodosRESUMEN
More than 30% of genes in higher eukaryotes are regulated by promoter-proximal pausing of RNA polymerase II (Pol II). Phosphorylation of Pol II CTD by positive transcription elongation factor b (P-TEFb) is a necessary precursor event that enables productive transcription elongation. The exact mechanism on how the sequestered P-TEFb is released from the 7SK snRNP complex and recruited to Pol II CTD remains unknown. In this report, we utilize mouse and human models to reveal methylphosphate capping enzyme (MePCE), a core component of the 7SK snRNP complex, as the cognate substrate for Jumonji domain-containing 6 (JMJD6)'s novel proteolytic function. Our evidences consist of a crystal structure of JMJD6 bound to methyl-arginine, enzymatic assays of JMJD6 cleaving MePCE in vivo and in vitro, binding assays, and downstream effects of Jmjd6 knockout and overexpression on Pol II CTD phosphorylation. We propose that JMJD6 assists bromodomain containing 4 (BRD4) to recruit P-TEFb to Pol II CTD by disrupting the 7SK snRNP complex.
In animals, an enzyme known as RNA polymerase II (Pol II for short) is a key element of the transcription process, whereby the genetic information contained in DNA is turned into messenger RNA molecules in the cells, which can then be translated to proteins. To perform this task, Pol II needs to be activated by a complex of proteins called P-TEFb; however, P-TEFb is usually found in an inactive form held by another group of proteins. Yet, it is unclear how P-TEFb is released and allowed to activate Pol II. Scientists have speculated that another protein called JMJD6 (Jumonji domain-containing 6) is important for P-TEFb to activate Pol II. Various roles for JMJD6 have been proposed, but its exact purpose remains unclear. Recently, two enzymes closely related to JMJD6 were found to be able to make precise cuts in other proteins; Lee, Liu et al. therefore wanted to test whether this is also true of JMJD6. Experiments using purified JMJD6 showed that it could make a cut in an enzyme called MePCE, which belongs to the group of proteins that hold P-TEFb in its inactive form. Lee, Liu et al. then tested the relationships between these proteins in living human and mouse cells. The levels of activated Pol II were lower in cells without JMJD6 and higher in those without MePCE. Together, the results suggest that JMJD6 cuts MePCE to release P-TEFb, which then activates Pol II. JMJD6 appears to know where to cut by following a specific pattern of elements in the structure of MePCE. When MePCE was mutated so that the pattern changed, JMJD6 was unable to cut it. These results suggest that JMJD6 and related enzymes belong to a new family of proteases, the molecular scissors that can cleave other proteins. The molecules that regulate transcription often are major drug targets, for example in the fight against cancer. Ultimately, understanding the role of JMJD6 might help to identify new avenues for cancer drug development.
Asunto(s)
Metiltransferasas/metabolismo , Factor B de Elongación Transcripcional Positiva/metabolismo , Receptores de Superficie Celular/metabolismo , Animales , Sitios de Unión , Western Blotting , Técnicas de Inactivación de Genes , Espectrometría de Masas , Ratones , Estructura Terciaria de Proteína , ARN Polimerasa II/metabolismo , Receptores de Superficie Celular/químicaRESUMEN
The generation of DNA double-strand breaks has historically been taught as the mechanism through which radiotherapy kills cancer cells. Recently, radiation-induced cytosolic DNA release and activation of the cGAS/STING pathway, with ensuing induction of interferon secretion and immune activation, have been recognized as important mechanisms for radiation-mediated anti-tumor efficacy. Here we demonstrate that radiation-induced activation of endogenous retroviruses (ERVs) also plays a major role in regulating the anti-tumor immune response during irradiation. Radiation-induced ERV-associated dsRNA transcription and subsequent activation of the innate antiviral MDA5/MAVS/TBK1 pathway led to downstream transcription of interferon-stimulated genes. Additionally, genetic knockout of KAP1, a chromatin modulator responsible for suppressing ERV transcription sites within the genome, enhanced the effect of radiation-induced anti-tumor response in vivo in two different tumor models. This anti-tumor response was immune-mediated and required an intact host immune system. Our findings indicate that radiation-induced ERV-dsRNA expression and subsequent immune response play critical roles in clinical radiotherapy, and manipulation of epigenetic regulators and the dsRNA-sensing innate immunity pathway could be promising targets to enhance the efficacy of radiotherapy and cancer immunotherapy.