RESUMEN
Broad X-ray emission lines from neutral and partially ionized iron observed in active galaxies have been interpreted as fluorescence produced by the reflection of hard X-rays off the inner edge of an accretion disk. In this model, line broadening and distortion result from rapid rotation and relativistic effects near the black hole, the line shape being sensitive to its spin. Alternative models in which the distortions result from absorption by intervening structures provide an equally good description of the data, and there has been no general agreement on which is correct. Recent claims that the black hole (2 × 10(6) solar masses) at the centre of the galaxy NGC 1365 is rotating at close to its maximum possible speed rest on the assumption of relativistic reflection. Here we report X-ray observations of NGC 1365 that reveal the relativistic disk features through broadened Fe-line emission and an associated Compton scattering excess of 10-30 kiloelectronvolts. Using temporal and spectral analyses, we disentangle continuum changes due to time-variable absorption from reflection, which we find arises from a region within 2.5 gravitational radii of the rapidly spinning black hole. Absorption-dominated models that do not include relativistic disk reflection can be ruled out both statistically and on physical grounds.
RESUMEN
Dysregulation of oncogenes by translocation to the IgH locus (14q32) is a seminal event in the pathogenesis of B-cell tumours. In multiple myeloma (MM), translocations to the IgH locus have been reported at an incidence of 20-60%. For most translocations, the partner chromosome is unknown (14q+); for the others, a diverse array of chromosomal partners have been identified, with 11q13 (cyclin D1) the only chromosome that is frequently involved. Recently, we developed a Southern-blot assay that detects translocation breakpoint fragments in most MM tumours, including those with no translocation detected by conventional karyotyping. In a continuing analysis of translocation in 21 myeloma cell lines and primary tumours, we show that the novel, karyotypically silent translocation t(4;14)(p16.3;q32.3) is present in five lines and at least three of ten primary tumours. The chromosome-4 breakpoints are clustered in a 70-kb region centromeric to the fibroblast growth factor receptor 3 gene (FGFR3), the apparent dysregulated oncogene. Two lines and one primary tumour with this translocation selectively express an FGFR3 allele containing activating mutations identified previously in thanatophoric dwarfism. We propose that after the t(4;14) translocation, somatic mutation during tumour progression frequently generates in FGFR3 protein that is active in the absence of ligand.
Asunto(s)
Regulación Neoplásica de la Expresión Génica , Mieloma Múltiple/genética , Mutación , Proteínas Tirosina Quinasas , Receptores de Factores de Crecimiento de Fibroblastos/genética , Translocación Genética/genética , Northern Blotting , Southern Blotting , Cromosomas Humanos Par 14/genética , Cromosomas Humanos Par 4/genética , Sondas de ADN , Humanos , Immunoblotting , Hibridación Fluorescente in Situ , Cariotipificación , Datos de Secuencia Molecular , Oncogenes/genética , Reacción en Cadena de la Polimerasa , ARN Mensajero/metabolismo , Receptor Tipo 3 de Factor de Crecimiento de Fibroblastos , Receptores de Factores de Crecimiento de Fibroblastos/biosíntesis , Células Tumorales CultivadasRESUMEN
Dysregulation of c-myc by translocation to the switch regions of the IgH locus occurs in most murine plasmacytomas. Translocations involving 14q32 have been reported in 20-40% of abnormal karyotypes from human multiple myeloma (MM), and involve a variety of loci. Using cytogenetics, FISH and a Southern blot assay, we analyzed 21 MM cells lines and one plasma cell leukemia and identified evidence of a 14q32 translocation in 20/22 samples. The partner loci involved are 11q13 in 6 (associated with cyclin D1 expression), 4p16 in 6 (associated with FGFR3 expression), unidentified in 3 and 1p13, 6, 8q24, 12q24, 16q23, and 21q22 once each. We conclude that conventional karyotypes underestimate the frequency of 14q32 translocations in MM, where they appear to be a nearly universal event. The translocations most frequently involve IgH switch regions, and include two recurrent partner loci (11q13 and 4p16) and a promiscuous array of other partner loci. Although c-myc appears to be cis-dysregulated frequently in MM, it is only rarely translocated to the IgH locus.
Asunto(s)
Cadenas Pesadas de Inmunoglobulina/genética , Mieloma Múltiple/genética , Mieloma Múltiple/inmunología , Translocación Genética , Animales , Cromosomas Humanos Par 14/genética , Cromosomas Humanos Par 21/genética , Cromosomas Humanos Par 8/genética , Genes de Inmunoglobulinas , Genes myc , Humanos , Región de Cambio de la Inmunoglobulina/genética , Ratones , Células Tumorales CultivadasRESUMEN
The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband x-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow's kinetic power larger than 10(46) ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution.
RESUMEN
One of the most severe side effects of anti-tumour chemotherapy is mucositis due to drug toxicity for rapidly dividing cells. We show here that anti-DXR monoclonal antibodies can prevent DXR-induced damage. Indeed, apoptosis, confined to the proliferative compartment of the basal mucosa, observed in the tongue of DXR-treated mice was completely inhibited by topical application of the anti-DXR antibodies.
Asunto(s)
Antibióticos Antineoplásicos/inmunología , Anticuerpos Monoclonales/uso terapéutico , Apoptosis/efectos de los fármacos , Doxorrubicina/inmunología , Estomatitis/prevención & control , Administración Tópica , Animales , Antibióticos Antineoplásicos/toxicidad , Anticuerpos Monoclonales/administración & dosificación , Anticuerpos Monoclonales/inmunología , Especificidad de Anticuerpos , Doxorrubicina/toxicidad , Evaluación Preclínica de Medicamentos , Femenino , Glositis/inducido químicamente , Glositis/patología , Glositis/prevención & control , Humanos , Ratones , Ratones Endogámicos BALB C , Mucosa Bucal/efectos de los fármacos , Mucosa Bucal/patología , Estomatitis/inducido químicamente , Estomatitis/patología , Lengua/efectos de los fármacos , Lengua/patologíaRESUMEN
Gastric mucosa-associated lymphoid tissue (MALT) lymphoma originates from reactive lymphocytic infiltrates during chronic gastritis, closely associated with Helicobacter pylori infection. MALT lymphomas may be either "low grade" or "high grade," and transformation from low grade to high grade can occur. To obtain information on the maturational state of MALT lymphoma cells, we investigated their ability to undergo isotype switch recombination, which together with immunoglobulin variable gene somatic mutation, contributes to normal B-cell maturation. Using specific probes for the immunoglobulin heavy-chain (IgH) switch regions, we found by Southern blot that 3 out of 5 low-grade cases and 2 out of 2 high-grade cases showed rearrangements within IgH switch regions, which appeared aberrant in 4 of the 5 cases. The cloning of two rearranged fragments from one low-grade and one high-grade case confirmed the aberrant nature of the rearranged fragments. A deletion from the switch mu region (S mu) to the first constant mu exon (C mu 1) and a second deletion from the second constant mu exon (C mu 2) to the gamma 3 region (gamma 3) was detected in the low-grade case. In the high-grade case, there was a deletion of the IgH intronic enhancer (E mu) and a 336-base pair (bp) insertion into the S mu region of a gene (KIAA0307) normally located at 15q24. These data demonstrate for the first time the ability of MALT lymphoma cells to undergo aberrant isotype switch recombinations, which might be directly involved in the development or progression of malignancy.
Asunto(s)
Linfocitos B/patología , Reordenamiento Génico de Cadena Pesada de Linfocito B , Cambio de Clase de Inmunoglobulina/genética , Cadenas Pesadas de Inmunoglobulina/genética , Isotipos de Inmunoglobulinas/genética , Linfoma no Hodgkin/genética , Neoplasias Gástricas/genética , Linfocitos B/química , Secuencia de Bases , Transformación Celular Neoplásica , Análisis Mutacional de ADN , ADN Nucleotidiltransferasas/metabolismo , ADN de Neoplasias/genética , Elementos de Facilitación Genéticos , Exones/genética , Genes de Inmunoglobulinas , Humanos , Regiones Constantes de Inmunoglobulina/genética , Región Variable de Inmunoglobulina/genética , Cadenas mu de Inmunoglobulina/genética , Intrones/genética , Linfoma no Hodgkin/patología , Datos de Secuencia Molecular , Alineación de Secuencia , Eliminación de Secuencia , Homología de Secuencia de Ácido Nucleico , Neoplasias Gástricas/patología , VDJ RecombinasasRESUMEN
In multiple myeloma, karyotopic 14q32 translocations have been identified at a variable frequency (10-60% in different studies). In the majority of cases, the partner chromosome has not been identified (14q+), and in the remaining cases, a diverse array of chromosomal partners has been implicated, with 11q13 being the most common. We developed a comprehensive Southern blot assay to identify and distinguish different kinds of immunoglobulin heavy chain (IgH) switch recombination events. Illegitimate switch recombination fragments (defined as containing sequences from only one switch region) are potential markers of translocation events into IgH switch regions and were identified in 15 of 21 myeloma cell lines, including seven of eight karyotyped lines that have no detectable 14q32 translocation. From all nine lines or tumor samples analyzed further, cloned illegitimate switch recombination fragments were confirmed to be IgH switch translocation breakpoints. In three of these cases, the translocation breakpoint was shown to be present in the primary tumor. These translocation breakpoints involve six chromosomal loci: 4p16.3 (two lines and the one tumor); 6; 8q24.13; 11q13.3 (in three lines); 16q23.1; and 21q22.1. We suggest that translocations into the IgH locus (i) are frequent (karyotypic 14q32 translocations and/or illegitimate switch recombination fragments are present in primary tumor samples and in 19 of 21 lines that we have analyzed); (ii) occur mainly in switch regions; and (iii) involve a diverse but nonrandom array (i.e., frequently 11q13 or 4p16) of chromosomal partners. This appears to be the most frequent genetic abnormality in multiple myeloma.
Asunto(s)
Cromosomas Humanos Par 11 , Cromosomas Humanos Par 14 , Cambio de Clase de Inmunoglobulina/genética , Cadenas Pesadas de Inmunoglobulina/genética , Mieloma Múltiple/genética , Translocación Genética , Secuencia de Bases , Southern Blotting , Línea Celular , Mapeo Cromosómico , Cartilla de ADN , Humanos , Datos de Secuencia Molecular , Mieloma Múltiple/inmunología , Reacción en Cadena de la Polimerasa , Recombinación GenéticaRESUMEN
Previously we reported that a karyotypically silent t(4;14)(p16. 3;q32.3) translocation is present in about 25% of multiple myeloma (MM) tumors, and causes overexpression of FGFR3, which is 50 to 100 kb telomeric to the 4p16 breakpoints. Frequent FGFR3 kinase activating mutations in MM with t(4;14) translocations substantiate an oncogenic role for FGFR3. We now report that the 4p16 breakpoints occur telomeric to and within the 5' introns of a novel gene, MMSET (Multiple Myeloma SET domain). In normal tissues, MMSET has a complex pattern of expression with a short form (647 amino acids [aa]) containing an HMG box and hath region, and an alternatively spliced long form (1365 aa) containing the HMG box and hath region plus 4 PHD fingers and a SET domain. Although t(4;14) translocation results in IgH/MMSET hybrid transcripts, overexpression of MMSET also occurs from endogenous promoters on 4p16. Given the homology to HRX/MLL1/ALL1 at 11q23 that is dysregulated by translocations in acute leukemia, we hypothesize that dysregulation of MMSET contributes to neoplastic transformation in MM with t(4;14) translocation. This is the first example of an IgH translocation that simultaneously dysregulates two genes with oncogenic potential: FGFR3 on der(14) and MMSET on der(4).
Asunto(s)
Proteínas Portadoras , Transformación Celular Neoplásica/genética , Cromosomas Humanos Par 14/genética , Cromosomas Humanos Par 4/genética , Genes de Inmunoglobulinas , Proteínas del Grupo de Alta Movilidad/genética , Cadenas Pesadas de Inmunoglobulina/genética , Mieloma Múltiple/genética , Proteínas de Fusión Oncogénica/genética , Proteínas Tirosina Quinasas , Receptores de Factores de Crecimiento de Fibroblastos/genética , Proteínas Represoras , Translocación Genética , Secuencia de Aminoácidos , Cromosomas Humanos Par 14/ultraestructura , Cromosomas Humanos Par 4/ultraestructura , Cartilla de ADN , ADN de Neoplasias/genética , Exones/genética , Regulación Neoplásica de la Expresión Génica , N-Metiltransferasa de Histona-Lisina , Humanos , Cariotipificación , Masculino , Datos de Secuencia Molecular , Mieloma Múltiple/patología , Proteínas de Fusión Oncogénica/biosíntesis , Poli A/metabolismo , Regiones Promotoras Genéticas , Empalme del ARN , ARN Mensajero/biosíntesis , ARN Mensajero/genética , ARN Neoplásico/biosíntesis , ARN Neoplásico/genética , Receptor Tipo 3 de Factor de Crecimiento de Fibroblastos , Testículo/metabolismo , Timo/metabolismo , Células Tumorales CultivadasRESUMEN
The HER-2 antigen, which is overexpressed in many breast carcinomas, is an ideal target for monoclonal antibodies due to its low expression in normal tissue and its homogeneous distribution in the tumor mass. We have developed and characterized the murine MAb MGR6 against HER-2, which is able to inhibit proliferation of tumor cells overexpressing HER-2. On the basis of these preclinical results, phase I studies in breast carcinoma patients were conducted and radiolocalization data indicated an antibody half life which directly paralleled that of other whole antibodies and thus resulting in a limited in vivo diagnostic capacity. To obtain a smaller reagent with possibly improved in vivo properties, a single chain variable fragment (scFv) of the original MGR6-producing hybridoma was generated by phage display technology. Biologically active MGR6 scFv was purified rapidly and at high yield by metal affinity chromatography. Competition FACS and ELISA analyses identified an epitope on the HER-2 extracellular domain that was shared by the scFv and the parental MAb. BlAcore analysis indicated a Koff of 9.3 x 10(-4) s(-1), similar to that of the intact MGR6 MAb. Distribution and elimination half-lives of MGR6 scFv, calculated from in vivo preclinical evaluations, were much faster (13 min and 6.2 h, respectively) than previously published results for the intact MAb (mean t1/2beta of 46 h). This represents a theoretical improvement in pharmacokinetics with respect to the parental murine MAb and points to the potential for utilizing this fragment in redirecting therapeutic agents, such as radioisotopes, to different human carcinomas overexpressing HER-2.