RESUMEN

Necroptosis is an alternative programmed cell death pathway that is unleashed in the absence of apoptosis and mediated by signaling complexes containing receptor-interating protein kinase 1 (RIPK1) and RIPK3. This form of cell death has recently been implicated in host defense system to eliminate pathogen-infected cells. However, only a few viral species such as herpes simplex virus (HSV) and cytomegalovirus (CMV) have evolved mechanisms inhibiting necroptosis to overcome host antiviral defense, which is important for successful pathogenesis. Here, we show that the γ-herpesvirus Epstein-Barr virus (EBV) blocks necroptosis in EBV-infected human nasopharyngeal epithelial cells and nasopharyngeal carcinoma cells. Our findings indicate that EBV-encoded latent membrane protein 1 (LMP1), which lacks an RIP homotypic interaction motif (RHIM) domain, has mechanisms distinct from RHIM signaling competition to inhibit this necroptotic pathway. Intriguingly, LMP1 interacts directly with both RIPK1 and RIPK3 through its C-terminal activation region. More importantly, LMP1 can modulate the post-translational modification of the two receptor-interacting proteins. We then show that LMP1-mediated promotion of K63-polyubiquitinated RIPK1, suppression of RIPK1 protein expression and inhibition of K63-polyubiquitinated RIPK3 induced a switch in cell fate from necroptotic death to survival. These findings provide direct evidence for the suppression of necroptosis by EBV and define a mechanism of LMP1 to interrupt the initiation process of necroptosis before necrosome formation.

Asunto(s)

Herpesvirus Humano 4/patogenicidad , Proteína Serina-Treonina Quinasas de Interacción con Receptores/genética , Proteínas de la Matriz Viral/genética , Apoptosis , Humanos , Necrosis , Proteína Serina-Treonina Quinasas de Interacción con Receptores/metabolismo , Ubiquitinación , Proteínas de la Matriz Viral/metabolismo

RESUMEN

Aberrant DNA methylation mediated by deregulation of DNA methyltransferases (DNMT) is a key hallmark of acute myeloid leukemia (AML), yet efforts to target DNMT deregulation for drug development have lagged. We previously demonstrated that upregulation of fatty acid-binding protein 4 (FABP4) promotes AML aggressiveness through enhanced DNMT1-dependent DNA methylation. Here, we demonstrate that FABP4 upregulation in AML cells occurs through vascular endothelial growth factor (VEGF) signaling, thus elucidating a crucial FABP4-DNMT1 regulatory feedback loop in AML biology. We show that FABP4 dysfunction by its selective inhibitor BMS309403 leads to downregulation of DNMT1, decrease of global DNA methylation and re-expression of p15INK4B tumor suppressor gene by promoter DNA hypomethylation in vitro, ex vivo and in vivo. Functionally, BMS309403 suppresses cell colony formation, induces cell differentiation, and, importantly, impairs leukemic disease progression in mouse models of leukemia. Our findings highlight AML-promoting properties of the FABP4-DNMT1 vicious loop, and identify an attractive class of therapeutic agents with a high potential for clinical use in AML patients. The results will also assist in establishing the FABP4-DNMT1 loop as a target for therapeutic discovery to enhance the index of current epigenetic therapies.

Asunto(s)

ADN (Citosina-5-)-Metiltransferasa 1/genética , Metilación de ADN/genética , Proteínas de Unión a Ácidos Grasos/genética , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patología , Animales , Diferenciación Celular/genética , Línea Celular , Línea Celular Tumoral , ADN/genética , Regulación hacia Abajo/genética , Células HEK293 , Humanos , Ratones , Regiones Promotoras Genéticas/genética , Transducción de Señal/genética , Regulación hacia Arriba/genética , Factor A de Crecimiento Endotelial Vascular/genética

RESUMEN

The nuclear factor of activated T cells (NFAT) family proteins are transcription factors that regulate the expression of pro-inflammatory cytokines and other genes during the immune response. Although the NFAT proteins have been extensively investigated in the immune system, their role in cancer progression remains controversial. Here, we report that NFAT3 is highly expressed in various skin cancer cell lines and tumor tissues. Knockdown of endogenous NFAT3 expression by short hairpin RNA (shRNA) significantly inhibited tumor cell proliferation, colony formation and anchorage-independent cell growth. Furthermore, results of the mammalian two-hybrid assay showed that cyclin-dependent kinase 3 (CDK3) directly interacted with NFAT3 and phosphorylated NFAT3 at serine 259 (Ser259), which enhanced the transactivation and transcriptional activity of NFAT3. The phosphorylation site of NFAT3 was critical for epidermal growth factor (EGF)-stimulated cell transformation of the HaCaT immortalized skin cell line and mutation of NFAT3 at Ser259 led to a reduction of colony formation in soft agar. We also found that overexpressing wildtype NFAT3, but not mutant NFAT3-S259A, promoted A431 xenograft tumor growth. Importantly, we showed that CDK3, NFAT3 and phosphorylated NFAT3-Ser259 were highly expressed in skin cancer compared with normal skin tissues. These results provided evidence supporting the oncogenic potential of NFAT3 and suggested that CDK3-mediated phosphorylation of NFAT3 has an important role in skin tumorigenesis.

Asunto(s)

Transformación Celular Neoplásica/metabolismo , Quinasa 3 Dependiente de Ciclina/metabolismo , Factores de Transcripción NFATC/metabolismo , Neoplasias Cutáneas/metabolismo , Neoplasias Cutáneas/patología , Animales , Línea Celular Tumoral , Proliferación Celular , Transformación Celular Neoplásica/genética , Quinasa 3 Dependiente de Ciclina/química , Expresión Génica , Regulación Neoplásica de la Expresión Génica , Humanos , Ratones , Factores de Transcripción NFATC/genética , Proteínas Oncogénicas/genética , Proteínas Oncogénicas/metabolismo , Fosforilación , Regiones Promotoras Genéticas , Unión Proteica , Neoplasias Cutáneas/genética , Especificidad por Sustrato , Activación Transcripcional

RESUMEN

Obesity is becoming more prevalent worldwide and is a major risk factor for cancer development. Acute myeloid leukemia (AML), the most common acute leukemia in adults, remains a frequently fatal disease. Here we investigated the molecular mechanisms by which obesity favors AML growth and uncovered the fatty acid-binding protein 4 (FABP4) and DNA methyltransferase 1 (DNMT1) regulatory axis that mediates aggressive AML in obesity. We showed that leukemia burden was much higher in high-fat diet-induced obese mice, which had higher levels of FABP4 and interleukin (IL)-6 in the sera. Upregulation of environmental and cellular FABP4 accelerated AML cell growth in both a cell-autonomous and cell-non-autonomous manner. Genetic disruption of FABP4 in AML cells or in mice blocked cell proliferation in vitro and induced leukemia regression in vivo. Mechanistic investigations showed that FABP4 upregulation increased IL-6 expression and signal transducer and activator of transcription factor 3 phosphorylation leading to DNMT1 overexpression and further silencing of the p15INK4B tumor-suppressor gene in AML cells. Conversely, FABP4 ablation reduced DNMT1-dependent DNA methylation and restored p15INK4B expression, thus conferring substantial protection against AML growth. Our findings reveal the FABP4/DNMT1 axis in the control of AML cell fate in obesity and suggest that interference with the FABP4/DNMT1 axis might be a new strategy to treat leukemia.

Asunto(s)

Metilación de ADN , Proteínas de Unión a Ácidos Grasos/metabolismo , Regulación Neoplásica de la Expresión Génica , Leucemia Mieloide Aguda/etiología , Leucemia Mieloide Aguda/patología , Obesidad/complicaciones , Animales , Apoptosis , Proliferación Celular , ADN (Citosina-5-)-Metiltransferasas/genética , ADN (Citosina-5-)-Metiltransferasas/metabolismo , Dieta Alta en Grasa/efectos adversos , Proteínas de Unión a Ácidos Grasos/genética , Humanos , Interleucina-6/genética , Interleucina-6/metabolismo , Leucemia Mieloide Aguda/metabolismo , Ratones , Ratones Endogámicos C57BL , Obesidad/inducido químicamente , Factor de Transcripción STAT3/genética , Factor de Transcripción STAT3/metabolismo , Células Tumorales Cultivadas

RESUMEN

Cyclin-dependent kinase 2 (CDK2) is a known regulator in the cell cycle control of the G1/S and S/G2 transitions. However, the role of CDK2 in tumorigenesis is controversial. Evidence from knockout mice as well as colon cancer cell lines indicated that CDK2 is dispensable for cell proliferation. In this study, we found that ectopic CDK2 enhances Ras (G12V)-induced foci formation and knocking down CDK2 expression markedly decreases epidermal growth factor (EGF)-induced cell transformation mediated through the downregulation of c-fos expression. Interestingly, CDK2 directly phosphorylates ELK4 at Thr194 and Ser387 and regulates the ELK4 transcriptional activity, which serves as a mechanism to regulate c-fos expression. In addition, ELK4 is overexpressed in melanoma and knocking down the ELK4 or CDK2 expression significantly attenuated the malignant phenotype of melanoma cells. Taken together, our study reveals a novel function of CDK2 in EGF-induced cell transformation and the associated signal transduction pathways. This indicates that CDK2 is a useful molecular target for the chemoprevention and therapy against skin cancer.

Asunto(s)

Quinasa 2 Dependiente de la Ciclina/genética , Melanoma/genética , Proteínas Proto-Oncogénicas c-fos/biosíntesis , Proteína Elk-4 del Dominio ets/biosíntesis , Animales , Ciclo Celular/genética , Línea Celular , Proliferación Celular , Transformación Celular Neoplásica/genética , Quinasa 2 Dependiente de la Ciclina/biosíntesis , Factor de Crecimiento Epidérmico/genética , Factor de Crecimiento Epidérmico/metabolismo , Humanos , Melanoma/patología , Ratones , Fosforilación , Activación Transcripcional/genética , Proteína Elk-4 del Dominio ets/genética

RESUMEN

Solar ultraviolet (UV) light is a major etiological factor in skin carcinogenesis, with solar UV-stimulated signal transduction inducing pathological changes and skin damage. The primary sensor of solar UV-induced cellular signaling has not been identified. We use an experimental system of solar simulated light (SSL) to mimic solar UV and we demonstrate that Fyn is a primary redox sensor involved in SSL-induced signal transduction. Reactive oxygen species (ROS) generated by SSL exposure directly oxidize Cys488 of Fyn, resulting in increased Fyn kinase activity. Fyn oxidation was increased in mouse skin after SSL exposure and Fyn-knockout mice formed larger and more tumors compared with Fyn wild-type mice when exposed to SSL for an extended period of time. Murine embryonic fibroblasts (MEFs) lacking Fyn and cells in which Fyn expression was knocked down were resistant to SSL-induced apoptosis. Furthermore, cells expressing mutant Fyn (C448A) were resistant to SSL-induced apoptosis. These findings suggest that Fyn acts as a regulatory nexus between solar UV, ROS and signal transduction during skin carcinogenesis.

Asunto(s)

Neoplasias Inducidas por Radiación/etiología , Proteínas Proto-Oncogénicas c-fyn/fisiología , Transducción de Señal/efectos de la radiación , Neoplasias Cutáneas/etiología , Animales , Apoptosis , Células Cultivadas , Ratones , Ratones Pelados , Proteína Quinasa C-delta/fisiología , Especies Reactivas de Oxígeno/metabolismo , Rayos Ultravioleta

RESUMEN

Reactive oxygen species (ROS) are chemically reactive molecules that perform essential functions in living organisms. Accumulating evidence suggests that many types of cancer cells exhibit elevated levels of ROS. Conversely, generation of ROS has become an effective method to kill cancer cells. (E)-3-hydroxy-3-(4-(4-nitrophenyl)-2-oxobut-3-en-1-yl) indolin-2-one, which is an NO2 group-containing compound designated herein as HOI-02, generated ROS and, in a dose-dependent manner, decreased esophageal cancer cell viability and inhibited anchorage-independent growth, followed by apoptosis and G2-M arrest. Moreover, results of an in vivo study using a patient-derived xenograft mouse model showed that HOI-02 treatment suppressed the growth of esophageal tumors, without affecting the body weight of mice. The expression of Ki-67 was significantly decreased with HOI-02 treatment. In addition, the phosphorylation of c-Jun, and expression of p21, cleaved caspase 3, and DCFH-DA were increased in the HOI-02-treated group compared with the untreated control group. In contrast, treatment of cells with (E)-3-(4-(4-aminophenyl)-2-oxobut-3-en-1-yl)-3-hydroxyindolin-2-one, which is an NH2 group-containing compound designated herein as HOI-11, had no effect. Overall, we identified HOI-02 as an effective NO2 group-containing compound that was an effective therapeutic or preventive agent against esophageal cancer cell growth.

Asunto(s)

Antineoplásicos/farmacología , Apoptosis/efectos de los fármacos , Neoplasias Esofágicas/tratamiento farmacológico , Puntos de Control de la Fase G2 del Ciclo Celular/efectos de los fármacos , Indoles/farmacología , Nitrobencenos/farmacología , Especies Reactivas de Oxígeno/metabolismo , Animales , Caspasa 3/metabolismo , Línea Celular Tumoral , Proliferación Celular , Supervivencia Celular , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Neoplasias Esofágicas/patología , Humanos , Masculino , Ratones SCID , Persona de Mediana Edad , Transducción de Señal , Factor de Transcripción AP-1/metabolismo , Carga Tumoral/efectos de los fármacos , Ensayos Antitumor por Modelo de Xenoinjerto

RESUMEN

Resveratrol (trans-3,5,4'-truhydroxystilbene) possesses a strong anticancer activity exhibited as the induction of apoptosis through p53 activation. However, the molecular mechanism and direct target(s) of resveratrol-induced p53 activation remain elusive. Here, the Ras-GTPase-activating protein SH3 domain-binding protein 1 (G3BP1) was identified as a potential target of resveratrol, and in vitro binding assay results using resveratrol-conjugated Sepharose 4B beads confirmed their direct binding. Depletion of G3BP1 significantly diminishes resveratrol-induced p53 expression and apoptosis. We also found that G3BP1 negatively regulates p53 expression by interacting with ubiquitin-specific protease 10 (USP10), a deubiquitinating enzyme of p53. Disruption of the interaction of p53 with USP10 by G3BP1 interference leads to the suppression of p53 deubiquitination. Resveratrol, on the other hand, directly binds to G3BP1 and prevents the G3BP1/USP10 interaction, resulting in enhanced USP10-mediated deubiquitination of p53, and consequently increased p53 expression. These findings disclose a novel mechanism of resveratrol-induced p53 activation and resveratrol-induced apoptosis by direct targeting of G3BP1.

Asunto(s)

Apoptosis/efectos de los fármacos , Proteínas Portadoras/antagonistas & inhibidores , Inhibidores Enzimáticos/farmacología , Estilbenos/farmacología , Proteína p53 Supresora de Tumor/metabolismo , Apoptosis/genética , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Línea Celular Tumoral , ADN Helicasas , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Células HEK293 , Humanos , Proteínas de Unión a Poli-ADP-Ribosa , Unión Proteica , ARN Helicasas , Proteínas con Motivos de Reconocimiento de ARN , Resveratrol , Proteína p53 Supresora de Tumor/genética , Ubiquitina Tiolesterasa/genética , Ubiquitina Tiolesterasa/metabolismo , Ubiquitinación/efectos de los fármacos , Ubiquitinación/genética

RESUMEN

Our goal in this work was to illustrate the Epstein-Barr virus (EBV)-modulated global biochemical profile and provide a novel metabolism-related target to improve the therapeutic regimen of nasopharyngeal carcinoma (NPC). We used a metabolomics approach to investigate EBV-modulated metabolic changes, and found that the exogenous overexpression of the EBV-encoded latent membrane protein 1 (LMP1) significantly increased glycolysis. The deregulation of several glycolytic genes, including hexokinase 2 (HK2), was determined to be responsible for the reprogramming of LMP1-mediated glucose metabolism in NPC cells. The upregulation of HK2 elevated aerobic glycolysis and facilitated proliferation by blocking apoptosis. More importantly, HK2 was positively correlated with LMP1 in NPC biopsies, and high HK2 levels were significantly associated with poor overall survival of NPC patients following radiation therapy. Knockdown of HK2 effectively enhanced the sensitivity of LMP1-overexpressing NPC cells to irradiation. Finally, c-Myc was demonstrated to be required for LMP1-induced upregulation of HK2. The LMP1-mediated attenuation of the PI3-K/Akt-GSK3beta-FBW7 signaling axis resulted in the stabilization of c-Myc. These findings indicate a close relationship between EBV and glycolysis in NPC. Notably, LMP1 is the key regulator of the reprogramming of EBV-mediated glycolysis in NPC cells. Given the importance of EBV-mediated deregulation of glycolysis, anti-glycolytic therapy might represent a worthwhile avenue of exploration in the treatment of EBV-related cancers.

Asunto(s)

Glucólisis , Neoplasias Nasofaríngeas/radioterapia , Neoplasias Nasofaríngeas/virología , Proteínas de la Matriz Viral/metabolismo , Apoptosis , Carcinoma , Línea Celular Tumoral , Proliferación Celular , Supervivencia Celular , Regulación Neoplásica de la Expresión Génica , Regulación Viral de la Expresión Génica , Glucosa/química , Herpesvirus Humano 4/metabolismo , Hexoquinasa/metabolismo , Humanos , Ácido Láctico/química , Metabolómica , Carcinoma Nasofaríngeo , Proteínas Proto-Oncogénicas c-myc/metabolismo , Fármacos Sensibilizantes a Radiaciones , Transducción de Señal

RESUMEN

Although the rate of development of drug resistance remains very high, 5-fluorouracil (5-Fu) is still the most common chemotherapeutic drug used for the treatment of colon cancer. A better understanding of the mechanism of why cancers develop resistance to 5-Fu could improve its therapeutic effect. Sometimes, antioxidants are used simultaneously with 5-Fu treatment. However, a recent clinical trial showed no advantage or even a harmful effect of combining antioxidants with 5-Fu compared with administration of 5-Fu alone. The mechanism explaining this phenomenon is still poorly understood. In this study, we show that 5-Fu can induce reactive oxygen species-dependent Src activation in colon cancer cells. Mouse embryonic fibroblasts that are deficient in Src showed a clear resistance to 5-Fu, and knocking down Src protein expression in colon cancer cells also decreased 5-Fu-induced apoptosis. We found that Src could interact with and phosphorylate caspase-7 at multiple tyrosine sites. Functionally, the tyrosine phosphorylation of caspase-7 increases its activity, thereby enhancing cellular apoptosis. When using 5-Fu and antioxidants together, Src activation was blocked, resulting in decreased 5-Fu-induced apoptosis. Our results provide a novel explanation as to why 5-Fu is not effective in combination with some antioxidants in colon cancer patients, which is important for clinical chemotherapy.

Asunto(s)

Antineoplásicos/farmacología , Antioxidantes , Caspasa 7/metabolismo , Neoplasias del Colon/metabolismo , Fluorouracilo/farmacología , Proteínas Proto-Oncogénicas pp60(c-src)/metabolismo , Apoptosis/efectos de los fármacos , Caspasa 7/genética , Línea Celular Tumoral , Neoplasias del Colon/tratamiento farmacológico , Neoplasias del Colon/enzimología , Neoplasias del Colon/genética , Contraindicaciones , Interacciones Farmacológicas , Humanos , Fosforilación/efectos de los fármacos , Proteínas Proto-Oncogénicas pp60(c-src)/genética

RESUMEN

RNF2, also known as Ring1B/Ring2, is a component of the polycomb repression complex 1. RNF2 is highly expressed in many tumors, suggesting that it might have an oncogenic function, but the mechanism is unknown. Here, we show that knockdown of RNF2 significantly inhibits both cell proliferation and colony formation in soft agar, and induces apoptosis in cancer cells. Knockdown of RNF2 in HCT116 p53(+/+) cells resulted in significantly more apoptosis than was observed in RNF2 knockdown HCT116 p53(-/-) cells, indicating that RNF2 knockdown-induced apoptosis is partially dependent on p53. Various p53-targeted genes were increased in RNF2 knockdown cells. Further studies revealed that in RNF2 knockdown cells, the p53 protein level was increased, the half-life of p53 was prolonged and p53 ubiquitination was decreased. In contrast, cells overexpressing RNF2 showed a decreased p53 protein level, a shorter p53 half-life and increased p53 ubiquitination. Importantly, we found that RNF2 directly binds with both p53 and MDM2 and promotes MDM2-mediated p53 ubiquitination. RNF2 overexpression could also increase the half-life of MDM2 and inhibit its ubiquitination. The regulation on p53 and MDM2 stability by RNF2 was also observed during the etoposide-induced DNA damage response. These results provide a possible mechanism explaining the oncogenic function of RNF2, and because RNF2 is important for cancer cell survival and proliferation, it might be an ideal target for cancer therapy or prevention.

Asunto(s)

Apoptosis/fisiología , Neoplasias/metabolismo , Complejo Represivo Polycomb 1/metabolismo , Proteínas Proto-Oncogénicas c-mdm2/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , Animales , Citometría de Flujo , Técnicas de Silenciamiento del Gen , Células HCT116 , Xenoinjertos , Humanos , Immunoblotting , Inmunoprecipitación , Ratones , Ratones Desnudos , Neoplasias/genética , Complejo Represivo Polycomb 1/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Ubiquitinación

RESUMEN

Many natural compounds derived from plants or microbes show promising potential for anticancer treatment, but few have been found to target energy-relevant regulators. In this study, we report that neoalbaconol (NA), a novel small-molecular compound isolated from the fungus, Albatrellus confluens, could target 3-phosphoinositide-dependent protein kinase 1 (PDK1) and inhibit its downstream phosphoinositide-3 kinase (PI3-K)/Akt-hexokinase 2 (HK2) pathway, which eventually resulted in energy depletion. By targeting PDK1, NA reduced the consumption of glucose and ATP generation, activated autophagy and caused apoptotic and necroptotic death of cancer cells through independent pathway. Necroptosis was remarkably induced, which was confirmed by several necroptosis-specific markers: the activation of autophagy, presence of necrotic morphology, increase of receptor-interacting protein 1 (RIP1)/RIP3 colocalization and interaction and rescued by necroptosis inhibitor necrostatin-1. The possibility that Akt overexpression reversed the NA-induced energy crisis confirmed the importance of the PDK1-Akt-energy pathway in NA-mediated cell death. Moreover, NA shows the capability to inhibit PI3-K/Akt signaling and suppress tumor growth in the nasopharyngeal carcinoma (NPC) nude mouse model. These results supported the feasibility of NA in anticancer treatments.

Asunto(s)

Proteínas Quinasas Dependientes de 3-Fosfoinosítido/metabolismo , Metabolismo Energético/efectos de los fármacos , Neoplasias/enzimología , Neoplasias/patología , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Sesquiterpenos/farmacología , Adenosina Trifosfato/metabolismo , Animales , Antineoplásicos/química , Antineoplásicos/farmacología , Antineoplásicos/uso terapéutico , Autofagia/efectos de los fármacos , Carcinoma , Muerte Celular/efectos de los fármacos , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Modelos Animales de Enfermedad , Regulación hacia Abajo/efectos de los fármacos , Ensayos de Selección de Medicamentos Antitumorales , Glucosa/metabolismo , Hexoquinasa/metabolismo , Ratones , Ratones Desnudos , Modelos Biológicos , Carcinoma Nasofaríngeo , Neoplasias Nasofaríngeas/tratamiento farmacológico , Neoplasias Nasofaríngeas/enzimología , Neoplasias Nasofaríngeas/patología , Necrosis , Neoplasias/tratamiento farmacológico , Sesquiterpenos/química , Sesquiterpenos/uso terapéutico , Transducción de Señal/efectos de los fármacos , Especificidad por Sustrato/efectos de los fármacos , Resultado del Tratamiento

RESUMEN

Cyclooxygenase-2 (COX-2) is an inducible enzyme that contributes to the generation of chronic inflammation in response to chemical carcinogens and environmental stresses, including ultraviolet B (UVB) irradiation. Although post-translational histone modifications are believed to have an important role in modulating transcriptional regulation of UVB-induced COX-2, the underlying biochemical mechanisms are completely unknown. Here, we show that UVB activates the p38 MAPK/MSK1 kinase cascade to phosphorylate histone H3 at Ser10 and Ser28, contributing to UVB-induced COX-2 expression. UVB has no effect on the global tri-methylation level of histone H3 (H3K4me3, H3K9me3, and H3K27me3). We observed that selected mammalian 14-3-3 proteins bind to UVB-induced phosphorylated histone H3 (Ser10 and Ser28). In particular, 14-3-3ɛ is critical for recruiting MSK1 and Cdk9 to the chromatin and subsequently phosphorylating the C-terminal domain of RNA polymerase II in the cox-2 promoter. We propose that histone H3 phosphorylation at Ser10 and Ser28 serve as critical switches to promote cox-2 gene expression by facilitating the recruitment of MSK1 and Cdk9 to the cox-2 promoter, thereby promoting RNA polymerase II phosphorylation.

Asunto(s)

Ciclooxigenasa 2/biosíntesis , Histonas/metabolismo , Proteínas 14-3-3/genética , Proteínas 14-3-3/metabolismo , Animales , Línea Celular , Quinasa 9 Dependiente de la Ciclina/genética , Quinasa 9 Dependiente de la Ciclina/metabolismo , Ciclooxigenasa 2/genética , Ciclooxigenasa 2/metabolismo , Activación Enzimática/efectos de la radiación , Células HEK293 , Histonas/genética , Humanos , Metilación , Ratones , Fosforilación , Regiones Promotoras Genéticas , ARN Polimerasa II/genética , ARN Polimerasa II/metabolismo , Proteínas Quinasas S6 Ribosómicas 90-kDa/genética , Proteínas Quinasas S6 Ribosómicas 90-kDa/metabolismo , Serina/metabolismo , Factor de Transcripción AP-1/genética , Factor de Transcripción AP-1/metabolismo , Rayos Ultravioleta , Proteínas Quinasas p38 Activadas por Mitógenos/genética , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismo

RESUMEN

The c-Jun transcription factor is a highly unstable oncoprotein. Several ubiquitin ligases mediate c-Jun degradation. However, c-Jun can be stabilized once it is phosphorylated at the N-terminus by c-Jun N-terminal kinases (JNKs) or other protein kinases. This phosphorylation decreases c-Jun ubiquitination and degradation. The underlying mechanism for this phenomenon is still unknown. Here, we show that receptor for activated C-kinase 1 (Rack1) can bind with c-Jun and ubiquitin ligase Fbw7 to form a complex. When c-Jun is phosphorylated at the N-terminus, c-Jun is released from the complex and cannot be ubiquitinated by Fbw7, which leads to increased stabilization and accumulation of c-Jun. These results reveal that Rack1 has a very important role in tumorigenesis by maintaining the stability of c-Jun that has been phosphorylated at its N-terminus by JNKs or other kinases.

Asunto(s)

Proteínas de Ciclo Celular/metabolismo , Proteínas F-Box/metabolismo , Proteínas de Unión al GTP/fisiología , Proteínas de Neoplasias/fisiología , Proteínas Proto-Oncogénicas c-jun/metabolismo , Receptores de Superficie Celular/fisiología , Ubiquitina-Proteína Ligasas/metabolismo , Animales , Línea Celular Tumoral , Transformación Celular Neoplásica , Proteína 7 que Contiene Repeticiones F-Box-WD , Técnicas de Silenciamiento del Gen , Ratones , Fosforilación , Estabilidad Proteica , Receptores de Cinasa C Activada , Ubiquitinación

RESUMEN

Cancer is a dynamic process that involves many complex factors, which may explain why a "magic bullet" cure for cancer has not been found. Death rates are still rising for many types of cancers, which possibly contributes to the increased interest in chemoprevention as an alternative approach to the control of cancer. This strategy for cancer control is based on the presumption that because cancer develops through a multi-step process, each step may be a prospective target for reversing or suppressing the process. Thus, the design and development of chemopreventive agents that act on specific and/or multiple molecular and cellular targets is gaining support as a rational approach to control cancer. Nutritional or dietary factors have attracted a great deal of interest because of their perceived ability to act as highly effective chemopreventive agents. They are professed as being generally safe and may have efficacy as chemopreventive agents by preventing or reversing premalignant lesions and/or reducing second primary tumor incidence. Many of these dietary compounds appear to act on multiple target signaling pathways. Some of the most interesting and well documented are resveratrol and components of tea, including EGCG, theaflavins and caffeine. This review will focus on recent work regarding three well-accepted cellular/molecular mechanisms that may at least partially explain the effectiveness of selected food factors, including those indicated above, as chemopreventive anti-promotion agents. These food compounds may act by: (1) inducing apoptosis in cancer cells; (2) inhibiting neoplastic transformation through the inhibition of AP-1 and/or NF-kappaB activation; and/or (3) suppressing COX-2 overexpression in cancer cells.

Asunto(s)

Anticarcinógenos/uso terapéutico , Neoplasias/prevención & control , Transducción de Señal/efectos de los fármacos , Animales , Quimioprevención , Humanos

RESUMEN

The mechanism of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumor promotion is still not well understood even though it is thought to be related to the protein kinase C/mitogen-activated protein kinase/AP-1 pathway. Recently, TPA was also found to induce epidermal growth factor receptor (EGFR) activity. Here, we investigated whether the EGFR is a necessary component for TPA-induced signal transduction associated with tumor promotion. We demonstrated that potent inhibitors of the EGFR, PD153035 and AG1478, blocked TPA-induced phosphorylation of extracellular signal-regulated kinases (ERKs), AP-1 activity, and cell transformation. Egfr gene deficiency blocked TPA-induced ERK activity and AP-1 binding activity. The blocking of the ectodomain of the EGFR by a monoclonal antibody depressed TPA-induced ERK activity and AP-1 DNA binding activity. The use of a neutralizing antibody for heparin-binding EGF, one of the ligands of EGFR, blocked TPA-induced phosphorylation of ERKs. BB-94, a potent inhibitor of matrix metalloproteinases, which are activators of ectodomain shedding of EGFR ligands, also blocked TPA-induced ERK activity, AP-1 DNA binding, and cell transformation but had no effect on EGF-induced signal transduction. Anti-EGFR, anti-heparin-binding EGF, and BB-94 each blocked TPA-induced EGFR phosphorylation, but only anti-EGFR could block EGF-induced EGFR phosphorylation. Based on these results, we conclude that the EGFR is required for mediating TPA-induced signal transduction. EGFR transactivation induced by TPA is a mechanism by which the EGFR mediates TPA-induced tumor promotion-related signal transduction.

Asunto(s)

Carcinógenos , Receptores ErbB/genética , Fenilalanina/análogos & derivados , Transducción de Señal , Acetato de Tetradecanoilforbol , Activación Transcripcional , Animales , Transformación Celular Neoplásica , Células Cultivadas , ADN/metabolismo , Relación Dosis-Respuesta a Droga , Embrión de Mamíferos/metabolismo , Inhibidores Enzimáticos/farmacología , Receptores ErbB/metabolismo , Ligandos , Ratones , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Modelos Biológicos , Fenilalanina/farmacología , Fosforilación , Unión Proteica , Estructura Terciaria de Proteína , Quinazolinas/farmacología , Tiofenos/farmacología , Factor de Transcripción AP-1 , Tirfostinos/farmacología

RESUMEN

N-terminal tail phosphorylation of histone H3 plays an important role in gene expression, chromatin remodeling, and chromosome condensation. Phosphorylation of histone H3 at serine 10 was shown to be mediated by RSK2, mitogen- and stress-activated protein kinase-1 (MSK1), and mitogen-activated protein kinases depending on the specific stimulation or stress. Our previous study showed that mitogen-activated protein kinases MAP kinases are involved in ultraviolet B-induced phosphorylation of histone H3 at serine 28 (Zhong, S., Zhong, Z., Jansen, J., Goto, H., Inagaki, M., and Dong, Z., J. Biol. Chem. 276, 12932-12937). However, downstream effectors of MAP kinases remain to be identified. Here, we report that H89, a selective inhibitor of the nucleosomal response, totally inhibits ultraviolet B-induced phosphorylation of histone H3 at serine 28. H89 blocks MSK1 activity but does not inhibit ultraviolet B-induced activation of MAP kinases p70/85(S6K), p90(RSK), Akt, and protein kinase A. Furthermore, MSK1 markedly phosphorylated serine 28 of histone H3 and chromatin in vitro. Transfection experiments showed that an N-terminal mutant MSK1 or a C-terminal mutant MSK1 markedly blocked MSK1 activity. Compared with wild-type MSK1, cells transfected with N-terminal or C-terminal mutant MSK1 strongly blocked ultraviolet B-induced phosphorylation of histone H3 at serine 28 in vivo. These data illustrate that MSK1 mediates ultraviolet B-induced phosphorylation of histone H3 at serine 28.

Asunto(s)

Proteínas Quinasas Dependientes de Calcio-Calmodulina/metabolismo , Histonas/metabolismo , Histonas/efectos de la radiación , Proteínas Serina-Treonina Quinasas , Proteínas Quinasas S6 Ribosómicas 90-kDa , Serina , Sulfonamidas , Rayos Ultravioleta , Animales , Línea Celular , Cromatina/metabolismo , Cromatina/efectos de la radiación , Activación Enzimática , Inhibidores Enzimáticos/farmacología , Epidermis , Histonas/química , Isoquinolinas/farmacología , Ratones , Nucleosomas/efectos de los fármacos , Nucleosomas/metabolismo , Nucleosomas/efectos de la radiación , Fosforilación , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-akt , Proteínas Recombinantes/metabolismo , Proteínas Quinasas S6 Ribosómicas/metabolismo , Proteínas Quinasas S6 Ribosómicas/efectos de la radiación , Transfección

RESUMEN

Epidemiological and animal-based investigations have indicated that the development of skin cancer is in part associated with poor dietary practices. Lipid content and subsequently the derived fatty acid composition of the diet are believed to play a major role in the development of tumorigenesis. Omega 3 (omega3) fatty acids, including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), can effectively reduce the risk of skin cancer whereas omega 6 (omega6) fatty acids such as arachidonic acid (AA) reportedly promote risk. To investigate the effects of fatty acids on tumorigenesis, we performed experiments to examine the effects of the omega3 fatty acids EPA and DHA and of the omega6 fatty acid AA on phorbol 12-tetradecanoate 13-acetate (TPA)-induced or epidermal growth factor (EGF)-induced transcription activator protein 1 (AP-1) transactivation and on the subsequent cellular transformation in a mouse epidermal JB6 cell model. DHA treatment resulted in marked inhibition of TPA- and EGF-induced cell transformation by inhibiting AP-1 transactivation. EPA treatment also inhibited TPA-induced AP-1 transactivation and cell transformation but had no effect on EGF-induced transformation. AA treatment had no effect on either TPA- or EGF-induced AP-1 transactivation or transformation, but did abrogate the inhibitory effects of DHA on TPA- or EGF-induced AP-1 transactivation and cell transformation in a dose-dependent manner. The results of this study demonstrate that the inhibitory effects of omega3 fatty acids on tumorigenesis are more significant for DHA than for EPA and are related to an inhibition of AP-1. Similarly, because AA abrogates the beneficial effects of DHA, the dietary ratio of omega6 to omega3 fatty acids may be a significant factor in mediating tumor development.

Asunto(s)

Transformación Celular Neoplásica/efectos de los fármacos , Ácidos Grasos Omega-3/farmacología , Ácidos Grasos Insaturados/farmacología , Piel/efectos de los fármacos , Factor de Transcripción AP-1/metabolismo , Activación Transcripcional/efectos de los fármacos , Animales , Adhesión Celular , Línea Celular , Factor de Crecimiento Epidérmico/farmacología , Ácidos Grasos Omega-6 , Genes Reporteros , Proteínas Quinasas JNK Activadas por Mitógenos , Cinética , Luciferasas/genética , Ratones , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Oligodesoxirribonucleótidos/metabolismo , Piel/citología , Piel/metabolismo , Acetato de Tetradecanoilforbol/farmacología , Factor de Transcripción AP-1/antagonistas & inhibidores , Transfección , Proteínas Quinasas p38 Activadas por Mitógenos

RESUMEN

Proteinase inhibitor I (Inh I) and proteinase inhibitor II (Inh II) from potato tubers are effective proteinase inhibitors of chymotrypsin and trypsin. Inh I and Inh II were shown to suppress irradiation-induced transformation in mouse embryo fibroblasts suggesting that they possess anticarcinogenic characteristics. We have previously demonstrated that Inh I and Inh II could effectively block UV irradiation-induced activation of transcription activator protein 1 (AP-1) in mouse JB6 epidermal cells, which mechanistically may explain their anticarcinogenic actions. In the present study, we investigated the effects of Inh I and Inh II on the expression and composition pattern of the AP-1 complex following stimulation by UV B (UVB) irradiation in the JB6 model. We found that Inh I and Inh II specifically inhibited UVB-induced AP-1, but not NFkappaB, activity in JB6 cells. Both Inh I and Inh II up-regulated AP-1 constituent proteins, JunD and Fra-2, and suppressed c-Jun and c-Fos expression and composition in bound AP-1 in response to UVB stimulation. This regulation of the AP-1 protein compositional pattern in response to Inh I or Inh II may be critical for the inhibition of UVB-induced AP-1 activity by these agents found in potatoes.

Asunto(s)

Proteínas Sanguíneas/farmacología , Solanum tuberosum/metabolismo , Factor de Transcripción AP-1/antagonistas & inhibidores , Secuencia de Bases , Proteínas Sanguíneas/aislamiento & purificación , Línea Celular , Cartilla de ADN , FN-kappa B/metabolismo , Factor de Transcripción AP-1/metabolismo , Factor de Transcripción AP-1/efectos de la radiación , Rayos Ultravioleta

RESUMEN

Previous studies have shown that c-Jun NH(2)-terminal kinase (JNK) belongs to the mitogen-activated protein kinase (MAPK) family of signal transduction components that are rapidly initiated and activated by many extracellular stimuli. However, the potential role of JNK in mediating tumor promotion and carcinogenesis is unclear. We show here that in JNK2-deficient (Jnk2(-/-)) mice, the multiplicity of papillomas induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) was lower than that in wild-type mice. Papillomas on wild-type mice grew rapidly and were well vascularized compared with Jnk2(-/-) mice. After the 12th week of TPA treatment, the mean number of tumors per mouse was 4.13-4.86 in wild-type mice but only 1.13-2.5 in Jnk2(-/-) mice. TPA induced phosphorylation of extracellular signal-regulated kinases and activator protein-1 DNA binding activity in wild-type mice, but the phosphorylation of extracellular signal-regulated kinases and activator protein-1 DNA binding were inhibited in Jnk2(-/-) mice. These data suggest that JNK2 is critical in the tumor promotion process.

Asunto(s)

Carcinoma de Células Escamosas/prevención & control , Proteínas Quinasas Activadas por Mitógenos/deficiencia , Papiloma/prevención & control , Neoplasias Cutáneas/prevención & control , Animales , Carcinógenos/antagonistas & inhibidores , Carcinógenos/toxicidad , Carcinoma de Células Escamosas/inducido químicamente , Carcinoma de Células Escamosas/enzimología , Transformación Celular Neoplásica/inducido químicamente , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/metabolismo , ADN/genética , ADN/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteína Quinasa 9 Activada por Mitógenos , Proteínas Quinasas Activadas por Mitógenos/genética , Papiloma/inducido químicamente , Papiloma/enzimología , Fosforilación/efectos de los fármacos , Neoplasias Cutáneas/inducido químicamente , Neoplasias Cutáneas/enzimología , Acetato de Tetradecanoilforbol/antagonistas & inhibidores , Acetato de Tetradecanoilforbol/toxicidad , Factor de Transcripción AP-1/metabolismo