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1.
Br J Dermatol ; 176(6): 1649-1652, 2017 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-27943234

RESUMEN

Cytotoxic T-lymphocyte-associated protein-4, programmed cell death protein and programmed cell death protein ligand 1 monoclonal antibodies (immune checkpoint inhibitors), are used to treat various malignancies. Their mechanism of action involves the inhibition of negative regulators of immune activation, resulting in immune-related adverse events (irAEs) including endocrinopathies, pneumonitis, colitis, hepatitis and dermatological events. Dermatological irAEs include maculopapular rash, pruritus, vitiligo, blistering disorders, mucocutaneous lichenoid eruptions, rosacea and the exacerbation of psoriasis. Alopecia secondary to immune checkpoint inhibitors has been reported in 1·0-2·0% of treated patients. Our objective is to characterize for the first time the clinicopathology of patients with alopecia areata (AA) secondary to immune checkpoint inhibitors, including the first report of anti-PD-L1 therapy-induced AA, and review of the literature. Four cases of patients who developed partial or complete alopecia during treatment with immune checkpoint inhibitors for underlying cancer were identified from our clinics. Methods include the review of the history and clinicopathologic features. Three patients (75%) had AA and one had universalis. Two patients had a resolution after topical, oral or intralesional therapies and one had a resolution after immunotherapy was discontinued; all regrown hair exhibited poliosis. One of the four patients had coincident onychodystrophy. This report describes a series of four patients who developed partial or complete alopecia (i.e. areata and universalis) during treatment with immune checkpoint inhibitor therapies for cancer. The recognition and management of hair-related irAEs are important for pretherapy counselling and interventions that contribute to maintaining optimal health-related quality of life in patients.


Asunto(s)
Alopecia Areata/inducido químicamente , Anticuerpos Monoclonales Humanizados/efectos adversos , Antígeno B7-H1/antagonistas & inhibidores , Antígeno CTLA-4/antagonistas & inhibidores , Adulto , Anciano , Carcinoma de Células Renales/tratamiento farmacológico , Quimioterapia Combinada , Femenino , Humanos , Inmunoterapia/efectos adversos , Neoplasias Renales/tratamiento farmacológico , Masculino , Melanoma/tratamiento farmacológico , Persona de Mediana Edad , Metástasis de la Neoplasia , Neoplasias Cutáneas/tratamiento farmacológico
2.
Ann Oncol ; 25(3): 663-668, 2014 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-24458473

RESUMEN

BACKGROUND: The clinical trials that reported benefit of the rapalogs temsirolimus and everolimus in advanced renal cell carcinoma (RCC) were primarily conducted in patients with clear-cell histology (ccRCC). We assessed outcome with these mammalian target of rapamicin (mTOR) inhibitors in two subsets of kidney cancer: sarcomatoid variant ccRCC and nonclear-cell RCC. PATIENTS AND METHODS: Baseline clinical features, information on prior treatment, and histologic subtypes were collected for patients previously treated with rapalogs for metastatic RCC of either nonclear phenotype or ccRCC with sarcomatoid features. Outcome was assessed centrally by a dedicated research radiologist for determination of tumor response, progression-free survival (PFS), and overall survival (OS). RESULTS: Eighty-five patients received temsirolimus (n = 59) or everolimus (n = 26). Nonclear-cell phenotypes included papillary (n = 14), chromophobe (n = 9), collecting duct (n = 4), translocation-associated (n = 3), and unclassified (n = 32) RCC. Twenty-three patients had clear-cell histology with sarcomatoid features. The response rate in assessable patients (n = 82) was 7% (all partial responses); 49% of patients achieved stable disease, and 44% had progressive disease as their best response. Tumor shrinkage was observed in 26 patients (32%). Median PFS and OS were 2.9 and 8.7 months, respectively. Nine patients (11%) were treated for ≥1 year, including cases of papillary (n = 3), chromophobe (n = 2), unclassified (n = 3) RCC, and ccRCC with sarcomatoid features (n = 1). No tumor shrinkages were observed for patients with collecting duct or translocation-associated RCC. CONCLUSIONS: A subset of patients with nonclear-cell and sarcomatoid variant ccRCC subtypes benefit from mTOR inhibitors, but most have poor outcome. Histologic subtype does not appear to be helpful in selecting patients for rapalog therapy. Future efforts should include the identification of predictive tissue biomarkers.


Asunto(s)
Carcinoma de Células Renales/tratamiento farmacológico , Neoplasias Renales/tratamiento farmacológico , Sirolimus/análogos & derivados , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Antineoplásicos/uso terapéutico , Carcinoma de Células Renales/mortalidad , Carcinoma de Células Renales/patología , Supervivencia sin Enfermedad , Everolimus , Femenino , Humanos , Inmunosupresores/uso terapéutico , Neoplasias Renales/mortalidad , Masculino , Persona de Mediana Edad , Inhibidores de Proteínas Quinasas/uso terapéutico , Estudios Retrospectivos , Sirolimus/uso terapéutico , Serina-Treonina Quinasas TOR/antagonistas & inhibidores , Resultado del Tratamiento , Adulto Joven
3.
Science ; 268(5210): 560-3, 1995 Apr 28.
Artículo en Inglés | MEDLINE | ID: mdl-7725102

RESUMEN

Epstein-Barr virus (EBV) nuclear antigen 2 (EBNA2) is a transcriptional activator that is essential for EBV-driven B cell immortalization. EBNA2 is targeted to responsive promoters through interaction with a cellular DNA binding protein, C promoter binding factor 1 (CBF1). A transcriptional repression domain has been identified within CBF1. This domain also interacts with EBNA2, and repression is masked by EBNA2 binding. Thus, EBNA2 acts by countering transcriptional repression. Mutation at amino acid 233 of CBF1 abolishes repression and correlates with a loss-of-function mutation in the Drosophila homolog Su(H).


Asunto(s)
Antígenos Virales/metabolismo , Proteínas de Unión al ADN/metabolismo , Regulación de la Expresión Génica , Proteínas Nucleares , Transactivadores/metabolismo , Transcripción Genética , Antígenos Virales/química , Proteínas de Unión al ADN/química , Antígenos Nucleares del Virus de Epstein-Barr , Células HeLa , Humanos , Proteína de Unión a la Señal Recombinante J de las Inmunoglobulinas , Modelos Genéticos , Mutación , Regiones Promotoras Genéticas , Transactivadores/química , Transfección
4.
Acta Radiol ; 49(9): 991-4, 2008 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-18651255

RESUMEN

BACKGROUND: Target therapy with a new class of epidermal growth factor receptor (EGFR) inhibitors shows improved clinical response in EGFR gene-mutated lung cancers. PURPOSE: To evaluate the use of computed tomography (CT)-guided core-needle biopsy specimens for the assessment of EGFR gene mutation in non-small-cell lung cancer (NSCLC). MATERIAL AND METHODS: Seventeen (nine males, eight females) patients with advanced NSCLC were enrolled in this study. All patients underwent CT-guided core-needle biopsy of the lung tumor prior to treatment with the EGFR inhibitor gefitinib. There were no life-threatening complications of biopsy. The specimens were sent fresh-frozen for EGFR mutation analysis and histopathological study. RESULTS: There were 12 (70.6%) EGFR gene mutants and five (29.4%) nonmutants. The objective response rate to gefitinib therapy was 73.3% (11 of 15 patients), with 91.7% (11 of 12 mutants) for the mutant group and 0% for the nonmutant group. CONCLUSION: CT-guided core-needle biopsy of advanced NSCLC enables the acquisition of sufficient tissue for EGFR gene mutation analysis.


Asunto(s)
Biopsia con Aguja/métodos , Carcinoma de Pulmón de Células no Pequeñas/genética , Genes erbB-1/genética , Neoplasias Pulmonares/genética , Tomografía Computarizada por Rayos X , Adulto , Anciano , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Carcinoma de Pulmón de Células no Pequeñas/patología , Receptores ErbB/antagonistas & inhibidores , Femenino , Gefitinib , Humanos , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/patología , Masculino , Persona de Mediana Edad , Mutación , Quinazolinas/uso terapéutico
5.
Mol Cell Biol ; 20(7): 2400-10, 2000 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-10713164

RESUMEN

Notch proteins are transmembrane receptors that mediate intercell communication and direct individual cell fate decisions. The activated intracellular form of Notch, NotchIC, translocates to the nucleus, where it targets the DNA binding protein CBF1. CBF1 mediates transcriptional repression through the recruitment of an SMRT-histone deacetylase-containing corepressor complex. We have examined the mechanism whereby NotchIC overcomes CBF1-mediated transcriptional repression. We identified SKIP (Ski-interacting protein) as a CBF1 binding protein in a yeast two-hybrid screen. Both CBF1 and SKIP are highly conserved evolutionarily, and the SKIP-CBF1 interaction is also conserved in assays using the Caenorhabditis elegans and Drosophila melanogaster SKIP homologs. Protein-protein interaction assays demonstrated interaction between SKIP and the corepressor SMRT. More surprisingly, SKIP also interacted with NotchIC. The SMRT and NotchIC interactions were mutually exclusive. In competition binding experiments SMRT displaced NotchIC from CBF1 and from SKIP. Contact with SKIP is required for biological activity of NotchIC. A mutation in the fourth ankyrin repeat that abolished Notch signal transduction did not affect interaction with CBF1 but abolished interaction with SKIP. Further, NotchIC was unable to block muscle cell differentiation in myoblasts expressing antisense SKIP. The results suggest a model in which NotchIC activates responsive promoters by competing with the SMRT-corepressor complex for contacts on both CBF1 and SKIP.


Asunto(s)
Repetición de Anquirina/genética , Proteínas de Unión al ADN/metabolismo , Proteínas de la Membrana/metabolismo , Proteínas Nucleares/metabolismo , Secuencia de Aminoácidos , Diferenciación Celular , Células Cultivadas , ADN sin Sentido , Humanos , Proteína de Unión a la Señal Recombinante J de las Inmunoglobulinas , Datos de Secuencia Molecular , Desarrollo de Músculos , Mutación , Co-Represor 2 de Receptor Nuclear , Coactivadores de Receptor Nuclear , Receptores Notch , Proteínas Represoras/metabolismo , Homología de Secuencia de Aminoácido , Factores de Transcripción
6.
Mol Cell Biol ; 16(3): 952-9, 1996 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-8622698

RESUMEN

The Notch/Lin-12/Glp-1 receptor family participates in cell-cell signaling events that influence cell fate decisions. Although several Notch homologs and receptor ligands have been identified, the nuclear events involved in this pathway remain incompletely understood. A truncated form of Notch, consisting only of the intracellular domain (NotchIC), localizes to the nucleus and functions as an activated receptor. Using both an in vitro binding assay and a cotransfection assay based on the two-hybrid principle, we show that mammalian NotchIC interacts with the transcriptional repressor CBF1, which is the human homolog of Drosophila Suppressor of Hairless. Cotransfection assays using segments of mouse NotchIC and CBF1 demonstrated that the N-terminal 114-amino-acid region of mouse NotchIC contains the CBF1 interactive domain and that the cdc10/ankyrin repeats are not essential for this interaction. This result was confirmed in immunoprecipation assays in which the N-terminal 114-amino-acid segment of NotchIC, but not the ankyrin repeat region, coprecipitated with CBF1. Mouse NotchIC itself is targeted to the transcriptional repression domain (aa179 to 361) of CBF1. Furthermore, transfection assays in which mouse NotchIC was targeted through Gal4-CBF1 or through endogenous cellular CBF1 indicated that NotchIC transactivates gene expression via CBF1 tethering to DNA. Transactivation by NotchIC occurs partially through abolition of CBF1-mediated repession. This same mechanism is used by Epstein-Barr virus EBNA2. Thus, mimicry of Notch signal transduction is involved in Epstein-Barr virus-driven immortalization.


Asunto(s)
Antígenos Virales/genética , Proteínas de Unión al ADN/genética , Proteínas Fúngicas/genética , Proteínas de la Membrana/metabolismo , Proteínas de Saccharomyces cerevisiae , Secuencia de Aminoácidos , Animales , Antígenos Virales/metabolismo , Secuencia de Bases , Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice , Proteínas de Unión al ADN/metabolismo , Proteínas de Drosophila , Drosophila melanogaster , Antígenos Nucleares del Virus de Epstein-Barr , Regulación de la Expresión Génica , Técnicas de Transferencia de Gen , Células HeLa , Humanos , Proteínas de la Membrana/genética , Datos de Secuencia Molecular , Receptores Notch , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Alineación de Secuencia , Transducción de Señal
7.
Kidney Cancer ; 1(1): 49-56, 2017 Jul 26.
Artículo en Inglés | MEDLINE | ID: mdl-30334004

RESUMEN

Background: Mutations in VHL, PBRM1, SETD2, BAP1, and KDM5C are common in clear cell renal cell carcinoma (ccRCC), and presence of certain mutations has been associated with outcomes in patients with non-metastatic disease. Limited information is available regarding the correlation between genomic alterations and outcomes in patients with metastatic disease, including response to VEGF-targeted therapy. Objective: To explore correlations between mutational profiles and cancer-specific outcomes, including response to standard VEGF-targeted agents, in patients with metastatic cc RCC. Methods: A retrospective review of 105 patients with metastatic ccRCC who had received systemic therapy and had targeted next-generation sequencing of tumors was conducted. Genomic alterations were correlated to outcomes, including overall survival and time to treatment failure to VEGF-targeted therapy. Results: The most frequent mutations were detected in VHL (83%), PBRM1 (51%), SETD2 (35%), BAP1 (24%), KDM5C (16%), and TERT (14%). Time to treatment failure with VEGF-targeted therapy differed significantly by PBRM1 mutation status (p = 0.01, median 12.0 months for MT versus 6.9 months for WT) and BAP1 mutation status (p = 0.01, median 6.4 months for MT versus 11.0 months for WT). Shorter overall survival was associated with TERT mutations (p = 0.03, median 29.6 months for MT versus 52.6 months for WT) or BAP1 mutations (p = 0.02, median 28.7 months for MT versus not reached for WT). Conclusions: Genomic alterations in ccRCC tumors have prognostic implications in patients with metastatic disease. BAP1 and TERT promoter mutations may be present in higher frequency than previously thought, and based on this data, deserve further study for their association with poor prognosis.

8.
J Endocrinol ; 179(3): 387-94, 2003 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-14656208

RESUMEN

An anaplastic thyroid cancer cell line, Thena, was recently established in our laboratory following radical thyroidectomy of a patient with anaplastic thyroid cancer. Microscopically, Thena cells were spindle-shaped or small round cells. Thena cells were reactive with cytokeratin AE1/AE3 antibodies, epithelial membrane antigen, interleukin (IL)-6, epithelial growth factor receptor, transforming growth factor (TGF)-alpha, vascular endothelial growth factor, and vimentin. Thena cells secreted high levels of IL-6, leukemia inhibitor factor (LIF), tumor necrosis factor (TNF)-alpha, and TGF-beta1 in the culture supernatants, as determined by enzyme-linked immunosorbent assay. When subcutaneously injected with Thena cells, athymic nude mice developed tumor masses in the skin within 2 weeks. Furthermore, Thena cells induced cachexia in these tumor-bearing mice. High levels of human IL-6, LIF and TGF-beta1 were detected in the mouse sera. To our knowledge, the Thena cell line is the first thyroid cancer cell line reported to induce cachexia in nude mice. This cachectic animal model is worthy of further study to explore the treatment of thyroid cancer-induced cachexia.


Asunto(s)
Caquexia/etiología , Citocinas/biosíntesis , Neoplasias de la Tiroides/complicaciones , Anciano , Animales , Caquexia/metabolismo , Caquexia/patología , Modelos Animales de Enfermedad , Femenino , Humanos , Ratones , Ratones Endogámicos BALB C , Ratones Desnudos , Trasplante de Neoplasias , Neoplasias de la Tiroides/metabolismo , Neoplasias de la Tiroides/ultraestructura , Tiroidectomía , Células Tumorales Cultivadas
9.
Math Biosci ; 103(2): 287-302, 1991 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-1804449

RESUMEN

This article extends the recent abridged life-table method of Hsieh. It generalizes the conventional discrete (abridged and complete) life tables into a continuous life table that can produce life-table functions at any age and develops a unified method of life-table construction that simplifies the disparate laborious procedures used in the traditional approach of constructing abridged and complete life tables. A set of precise procedures based on the complete cubic spline for the main body of the table and a mortality law for advanced ages is developed for estimating the basic and nonbasic life-table functions from a given mortality schedule. The proposed method can also produce more life-table functions than other existing methods. The method is illustrated with Canadian data.


Asunto(s)
Tablas de Vida , Humanos , Mortalidad
10.
Angiology ; 49(5): 415-8, 1998 May.
Artículo en Inglés | MEDLINE | ID: mdl-9591535

RESUMEN

A 43-year-old man presenting with symptoms of congestive heart failure, cardiomegaly, and impaired left ventricular (LV) function was diagnosed as having a huge left renal arteriovenous (AV) fistula. The AV fistula might be attributed to a gunshot wound suffered during his military service twenty years ago. Percutaneous transcatheter arterial embolization utilizing multiple spring coils in conjunction with cyanoacrylic glue successfully occluded the fistula, with subsequent improvement of LV function and reduction of LV size on his serial echocardiographic follow-up.


Asunto(s)
Fístula Arteriovenosa/etiología , Riñón/lesiones , Arteria Renal/lesiones , Vena Cava Inferior/lesiones , Heridas por Arma de Fuego/complicaciones , Adulto , Fístula Arteriovenosa/diagnóstico por imagen , Fístula Arteriovenosa/terapia , Cardiomegalia/etiología , Cardiomegalia/terapia , Cianoacrilatos/uso terapéutico , Ecocardiografía , Embolización Terapéutica/instrumentación , Embolización Terapéutica/métodos , Estudios de Seguimiento , Insuficiencia Cardíaca/etiología , Insuficiencia Cardíaca/terapia , Humanos , Masculino , Nefrectomía/efectos adversos , Disfunción Ventricular Izquierda/etiología , Disfunción Ventricular Izquierda/terapia , Función Ventricular Izquierda , Heridas por Arma de Fuego/cirugía
11.
J Appl Psychol ; 99(5): 816-30, 2014 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-24820927

RESUMEN

In this study, we investigated whether team-level knowledge sharing moderates the effects of individual-level expertise dissimilarity on individual employees' creativity in research and development (R&D) project teams. Expertise dissimilarity--defined as the difference in expertise and knowledge between a focal team member and her or his fellow team members--was operationalized in terms of the research department to which each member belonged. In Study 1, multilevel analyses of data collected from 200 members of 40 R&D project teams in a telecommunications company revealed that a team member with expertise dissimilar to that of her or his teammates was more likely to exhibit creativity when the project team as a whole engaged in higher levels of tacit, rather than explicit, knowledge sharing. In contrast, a member whose expertise was similar to that of her or his teammates was more likely to exhibit creative behavior when the team engaged in higher levels of explicit, rather than tacit, knowledge sharing. These findings were largely replicated in Study 2 using data collected from 82 members of 25 project teams from another telecommunications company.


Asunto(s)
Conducta Cooperativa , Creatividad , Empleo , Conocimiento , Adulto , Femenino , Humanos , Masculino
13.
Br J Dermatol ; 158(3): 592-6, 2008 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-18070211

RESUMEN

BACKGROUND: Hand-foot skin reaction is a distinctive cutaneous side-effect of antineoplastic kinase inhibitor-targeted therapy. Severe hand-foot skin reaction requires postponement of treatment or dose reduction. Histopathological studies of skin toxicity associated with kinase inhibitors are currently unavailable. OBJECTIVES: To report the clinical and histopathological findings of hand-foot skin reaction produced by the multikinase inhibitor sorafenib. METHODS: Nine patients with metastatic carcinoma-seven with renal cell carcinoma (RCC), one with melanoma and one with hepatocellular carcinoma (HCC)-received continuous, oral sorafenib 400 mg twice daily. Hand-foot skin reaction was defined and graded according to National Cancer Institute Common Toxicity Criteria 3.0. Biopsies from lesions of erythematous scaly or blistering skin were obtained from five cases (four RCC and one HCC). RESULTS: Seven of the nine (78%) patients developed hand-foot skin reaction characterized by well-demarcated, tender, erythematous papules and plaques with greyish blisters or hyperkeratotic, callus-like formations on palmoplantar surfaces and distal phalanges. Skin biopsy of hand-foot skin reaction lesions revealed epidermal acanthosis, papillomatosis, parakeratosis, dispersed dyskeratotic cells and keratinocyte vacuolar degeneration. Other skin toxicities included angular cheilitis, seborrhoeic dermatitis and perianal dermatitis. CONCLUSIONS: The clinical manifestations and histopathological features of sorafenib-induced skin reactions are unique. The most relevant histopathological findings of hand-foot skin reaction include keratinocyte vacuolar degeneration, the presence of intracytoplasmic eosinophilic bodies, and intraepidermal blisters in the stratum malpighii. Further studies are warranted to elucidate the mechanisms of this novel multitargeted kinase inhibitor-associated skin reaction.


Asunto(s)
Bencenosulfonatos/efectos adversos , Vesícula/inducido químicamente , Erupciones por Medicamentos/etiología , Dermatosis del Pie/inducido químicamente , Dermatosis de la Mano/inducido químicamente , Inhibidores de Proteínas Quinasas/efectos adversos , Piridinas/efectos adversos , Anciano , Anciano de 80 o más Años , Bencenosulfonatos/administración & dosificación , Vesícula/patología , Carcinoma de Células Renales/complicaciones , Carcinoma de Células Renales/tratamiento farmacológico , Erupciones por Medicamentos/patología , Femenino , Dermatosis del Pie/patología , Dermatosis de la Mano/patología , Humanos , Neoplasias Renales/complicaciones , Neoplasias Renales/tratamiento farmacológico , Masculino , Persona de Mediana Edad , Niacinamida/análogos & derivados , Compuestos de Fenilurea , Inhibidores de Proteínas Quinasas/administración & dosificación , Piridinas/administración & dosificación , Sorafenib , Resultado del Tratamiento
14.
Biom J ; 33(2): 143-62, 1991.
Artículo en Inglés | MEDLINE | ID: mdl-12343327

RESUMEN

"In this paper we lay the foundation of life table construction by unifying the existing life table methods. We also present a new method of constructing current (period) abridged life tables.... The development includes (1) a careful formulation and computation of age-specific death rates, (2) derivation of a new set of formulas for computing the survivorship function from the observed age-specific death rates and populations, (3) estimation of the main life table functions by spline interpolation, integration and differentiation, and (4) use of a quadratic and a Gompertz function to close the life table.... The method is illustrated with construction of abridged life tables using Canadian data."


Asunto(s)
Esperanza de Vida , Tablas de Vida , Métodos , Modelos Teóricos , Mortalidad , Américas , Canadá , Demografía , Países Desarrollados , Longevidad , América del Norte , Población , Dinámica Poblacional , Investigación
15.
J Math Biol ; 5(1): 75-86, 1977 Dec 27.
Artículo en Inglés | MEDLINE | ID: mdl-753909

RESUMEN

The lifetime distribution is formulated in terms of g(t), defined as the ratio of the hazard function to the tail probability function, to study the properties of the lifetime distribution. A criterion is provided for the asymptotic behaviour of g(t) and the hazard function. Criteria for the existence and non-existence of the moments of any probability distribution of a non-negative random variable are obtained in terms of the derivatives of g(t). Examples are given to illustrate the use of the criteria and applications made to stochastic models of population growth as well as other lifetime distributions.


Asunto(s)
Genética de Población , Modelos Biológicos , Procesos Estocásticos , Factores de Tiempo
16.
Biom J ; 31(3): 339-57, 1989.
Artículo en Inglés | MEDLINE | ID: mdl-12282507

RESUMEN

"This paper aims to identify net and partial-crude probabilities in the competing-risk life table context, by using probabilistic approaches. Five types of lifelength random variables are defined to formulate these nonidentifiable probabilities. General expressions for net and partial-crude probabilities are first derived under independent risks assumptions. Two sets of explicit formulas for estimating the net and partial-crude probabilities are then derived in terms of the identifiable overall and crude probabilities by making the additional assumption of piecewise uniform distribution of the lifelength random variables. A study of the degree to which nonidentifiability can affect the net and partial-crude probabilities in a variety of situations is developed. An example from cross-sectional studies is employed to illustrate the methodology developed."


Asunto(s)
Tablas de Vida , Modelos Teóricos , Probabilidad , Factores de Riesgo , Estadística como Asunto , Biología , Demografía , Investigación
17.
J Virol ; 71(3): 1938-45, 1997 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-9032325

RESUMEN

EBNA2 is essential for immortalization of B cells by Epstein-Barr virus. EBNA2 is tethered to responsive promoters through a cellular factor, CBF1. CBF1 also binds to the activated form of mammalian Notch1, providing a linkage between EBNA2 function and Notch signalling. However, Notch2 is the predominant form expressed in spleen. The degree to which these Notch homologs are functionally convergent is not known. We present evidence that Notch2 also signals through CBF1. As is the case for Notch1, Notch2 interacted with the minimal repression domain of CBF1 and was targeted to CBF1 through the intracellular, subtransmembrane domain. Additional characterization suggested that the interaction domain of Notch may be bipartite. The intracellular domain of Notch2 (Notch2IC) located to the nucleus. This activated form of Notch2 transactivated expression of a target gene containing upstream CBF1 binding sites. The use of CBF1 mutants carrying amino acid substitutions in the transcriptional repression domain revealed that activation of gene expression by Notch2 is also based on masking of CBF1-mediated repression. Targeting of Notch1 and targeting of Notch2 were found to be identical and distinguishable from targeting by EBNA2. Mutation of CBF1 at codons 249 to 251 abolished interaction with both Notch proteins but not with EBNA2. In a biological examination of Notch2 function in muscle cells, Notch2IC activated endogenous HES-1 gene expression and blocked muscle cell differentiation. Overall, the data imply that at least a subset of the intracellular events following signalling in cells expressing Notch2 are common to those in Notch1-expressing cells. The concept that EBNA2 functions by mimicking Notch signalling is therefore viable whether cells are expressing Notch1 or Notch2.


Asunto(s)
Proteínas Aviares , Diferenciación Celular , Herpesvirus Humano 4/metabolismo , Proteínas Oncogénicas , Proteínas Proto-Oncogénicas/metabolismo , Receptores de Superficie Celular/metabolismo , Factores de Transcripción , Proteínas Virales , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico , Sitios de Unión , Transporte Biológico , Línea Celular , Núcleo Celular/metabolismo , Antígenos Nucleares del Virus de Epstein-Barr/metabolismo , Factores de Transcripción Forkhead , Expresión Génica , Genes Reporteros , Células HeLa , Proteínas de Homeodominio/genética , Humanos , Células Jurkat , Luciferasas/genética , Proteínas de la Membrana/metabolismo , Ratones , Proteínas Proto-Oncogénicas/genética , Ratas , Receptor Notch1 , Receptor Notch2 , Receptores de Superficie Celular/genética , Transducción de Señal/fisiología , Relación Estructura-Actividad , Factor de Transcripción HES-1 , Activación Transcripcional , Células Tumorales Cultivadas , Regulación hacia Arriba
18.
J Virol ; 74(4): 1939-47, 2000 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-10644367

RESUMEN

EBNA2 is essential for Epstein-Barr virus (EBV) immortalization of B lymphocytes. EBNA2 functions as a transcriptional activator and targets responsive promoters through interaction with the cellular DNA binding protein CBF1. We have examined the mechanism whereby EBNA2 overcomes CBF1-mediated transcriptional repression. A yeast two-hybrid screen performed using CBF1 as the bait identified a protein, SKIP, which had not previously been recognized as a CBF1-associated protein. Protein-protein interaction assays demonstrated contacts between SKIP and the SMRT, CIR, Sin3A, and HDAC2 proteins of the CBF1 corepressor complex. Interestingly, EBNA2 also interacted with SKIP in glutathione S-transferase affinity and mammalian two-hybrid assays and colocalized with SKIP in immunofluorescence assays. Interaction with SKIP was not affected by mutation of EBNA2 conserved region 6, the CBF1 interaction region, but was abolished by mutation of conserved region 5. Mutation of conserved region 5 also severely impaired EBNA2 activation of a reporter containing CBF1 binding sites. Thus, interaction with both CBF1 and SKIP is necessary for efficient promoter activation by EBNA2. A model is presented in which EBNA2 competes with the SMRT-corepressor complex for contacts on SKIP and CBF1.


Asunto(s)
Proteínas de Unión al ADN/metabolismo , Antígenos Nucleares del Virus de Epstein-Barr , Regulación de la Expresión Génica , Proteínas Nucleares/fisiología , Regiones Promotoras Genéticas , Proteínas Virales/metabolismo , Secuencia de Aminoácidos , Sitios de Unión , Línea Celular Transformada , Proteínas de Unión al ADN/genética , Células HeLa , Histona Desacetilasa 2 , Histona Desacetilasas/metabolismo , Humanos , Proteína de Unión a la Señal Recombinante J de las Inmunoglobulinas , Datos de Secuencia Molecular , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Co-Represor 2 de Receptor Nuclear , Coactivadores de Receptor Nuclear , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Proteínas Represoras/metabolismo , Complejo Correpresor Histona Desacetilasa y Sin3 , Factores de Transcripción , Transfección , Proteínas Virales/genética
19.
Proc Natl Acad Sci U S A ; 96(1): 23-8, 1999 Jan 05.
Artículo en Inglés | MEDLINE | ID: mdl-9874765

RESUMEN

CBF1 is a member of the CSL family of DNA binding factors, which mediate either transcriptional repression or transcriptional activation. CSL proteins play a central role in Notch signaling and in Epstein-Barr virus-induced immortalization. Notch is a transmembrane protein involved in cell-fate decisions, and the cytoplasmic domain of Notch (NotchIC) targets CBF1. The Epstein-Barr virus-immortalizing protein EBNA2 activates both cellular and viral gene expression by targeting CBF1 and mimicking NotchIC. We have examined the mechanism of CBF1-mediated repression and show that CBF1 binds to a unique corepressor, CBF1 interacting corepressor (CIR). A CIR homolog is encoded by Caenorhabditis elegans, indicating that CIR is evolutionarily conserved. Two CBF1 mutants that were unable to bind CIR did not function as repressors, suggesting that targeting of CIR to CBF1 is an important component of repression. When expressed as a Gal4 fusion protein, CIR repressed reporter gene expression. CIR binds to histone deacetylase and to SAP30 and serves as a linker between CBF1 and the histone deacetylase complex.


Asunto(s)
Proteínas de Unión al ADN/metabolismo , Histona Desacetilasas/metabolismo , Proteínas Nucleares , Proteínas Represoras/metabolismo , Secuencia de Aminoácidos , Animales , Sitios de Unión , Caenorhabditis elegans , Núcleo Celular/ultraestructura , Chlorocebus aethiops , Secuencia Conservada , Proteínas de Unión al ADN/aislamiento & purificación , Técnica del Anticuerpo Fluorescente Indirecta , Humanos , Proteína de Unión a la Señal Recombinante J de las Inmunoglobulinas , Datos de Secuencia Molecular , Unión Proteica , Proteínas Recombinantes de Fusión/metabolismo , Proteínas Represoras/genética , Proteínas Represoras/aislamiento & purificación , Homología de Secuencia de Aminoácido , Células Vero
20.
J Virol ; 68(9): 5375-83, 1994 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-8057421

RESUMEN

The EBNA-2 protein is essential for the establishment of a latent Epstein-Barr virus (EBV) infection and for B-cell immortalization. EBNA-2 functions as a transcriptional activator that modulates viral latency gene expression as well as the expression of cellular genes, including CD23. We recently demonstrated that EBNA-2 transactivation of the EBV latency C promoter (Cp) is dependent on an interaction with a cellular DNA-binding protein, CBF1, for promoter targeting. To determine whether targeting via CBF1 is a common mechanism for EBNA-2-mediated transactivation, we have examined the requirements for activation of the cellular CD23 promoter. Binding of CBF1 to a 192-bp mapped EBNA-2-responsive region located at position -85 bp to -277 bp upstream of the CD23 promoter was detected in electrophoretic mobility shift assays. The identity of the bound protein as CBF1 was established by showing that the bound complex was competed for by the CBF1 binding site from the EBV Cp, that the bound protein could be supershifted with a bacterially expressed fusion protein' containing amino acids 252 to 425 of EBNA-2 but was unable to interact with a non-CBF1-binding EBNA-2 mutant (WW323SR), and that in UV cross-linking experiments, the Cp CBF1 binding site and the CD23 probe bound proteins of the same size. The requirement for interaction with CBF1 was demonstrated in a transient cotransfection assay in which the multimerized 192-bp CD23 response region was transactivated by wild-type EBNA-2 but not by the WW323SR mutant. Reporter constructions carrying multimerized copies of the 192-bp CD23 response region or multimers of the CBF1 binding site from the CD23 promoter were significantly less responsive to EBNA-2 transactivation than equivalent constructions carrying a multimerized region from the Cp or multimers of the CBF1 binding site from the Cp. Direct binding and competition assays using 30-mer oligonucleotide probes representing the individual CBF1 binding sites indicated that CBF1 bound less efficiently to the CD23 promoter and the EBV LMP-1 promoter sites than to the Cp site. To investigate the basis for this difference, we synthesized a series of oligonucleotides carrying mutations across the CBF1 binding site and used these as competitors in electrophoretic mobility shift assays. The competition experiments indicated that a central core sequence, GTGGGAA, common to all known EBNA-2-responsive elements, is crucial for CBF1 binding. Flanking sequences on either side of this core influence the affinity for CBF1.(ABSTRACT TRUNCATED AT 400 WORDS)


Asunto(s)
Antígenos Virales/fisiología , Proteínas de Unión al ADN/fisiología , Proteínas Fúngicas/fisiología , Regulación Viral de la Expresión Génica , Herpesvirus Humano 4/genética , Proteínas Oncogénicas Virales/genética , Regiones Promotoras Genéticas , Receptores de IgE/genética , Proteínas de Saccharomyces cerevisiae , Proteínas de la Matriz Viral/genética , Secuencia de Bases , Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice , Sitios de Unión , Núcleo Celular/química , Secuencia de Consenso , Cartilla de ADN/química , Antígenos Nucleares del Virus de Epstein-Barr , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , ARN Mensajero/genética , Alineación de Secuencia , Homología de Secuencia de Ácido Nucleico , Relación Estructura-Actividad , Activación Transcripcional , Latencia del Virus
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