RESUMEN
The t(4;14) translocation occurs frequently in multiple myeloma (MM) and results in the simultaneous dysregulated expression of 2 potential oncogenes, FGFR3 (fibroblast growth factor receptor 3) from der(14) and multiple myeloma SET domain protein/Wolf-Hirschhorn syndrome candidate gene 1 from der(4). It is now shown that myeloma cells carrying a t(4;14) translocation express a functional FGFR3 that in some cases is constitutively activated by the same mutations that cause thanatophoric dysplasia. As with activating mutations of K-ras and N-ras, which are reported in approximately 40% of patients with MM, activating mutations of FGFR3 occur during tumor progression. However, the constitutive activation of ras and FGFR3 does not occur in the same myeloma cells. Thus the activated forms of these proteins appear to share an overlapping role in tumor progression, suggesting that they also share the signaling cascade. Consistent with this prediction, it is shown that activated FGFR3-when expressed at levels similar to those seen in t(4;14) myeloma-is an oncogene that acts through the MAP kinase pathway to transform NIH 3T3 cells, which can then generate tumors in nude mice. Thus, FGFR3, when overexpressed in MM, may be not only oncogenic when stimulated by FGF ligands in the bone marrow microenvironment, but is also a target for activating mutations that enable FGFR3 to play a ras-like role in tumor progression.
Asunto(s)
Mieloma Múltiple/genética , Proteínas Tirosina Quinasas , Receptores de Factores de Crecimiento de Fibroblastos/genética , Células 3T3 , Animales , Transformación Celular Neoplásica , Progresión de la Enfermedad , Expresión Génica , Genes ras , Humanos , Sistema de Señalización de MAP Quinasas , Ratones , Ratones Desnudos , Modelos Genéticos , Mieloma Múltiple/metabolismo , Mieloma Múltiple/patología , Mutación , Proteínas Oncogénicas/genética , Proteínas Oncogénicas/metabolismo , Receptor Tipo 3 de Factor de Crecimiento de Fibroblastos , Receptores de Factores de Crecimiento de Fibroblastos/metabolismo , Transfección , Translocación Genética , Células Tumorales CultivadasRESUMEN
Translocations involving c-myc and an Ig locus have been reported rarely in human multiple myeloma (MM). Using specific fluorescence in situ hybridization probes, we show complex karyotypic abnormalities of the c-myc or L-myc locus in 19 of 20 MM cell lines and approximately 50% of advanced primary MM tumors. These abnormalities include unusual and complex translocations and insertions that often juxtapose myc with an IgH or IgL locus. For two advanced primary MM tumors, some tumor cells contain a karyotypic abnormality of the c-myc locus, whereas other tumor cells do not, indicating that this karyotypic abnormality of c-myc occurs as a late event. All informative MM cell lines show monoallelic expression of c-myc. For Burkitt's lymphoma and mouse plasmacytoma tumors, balanced translocation that juxtaposes c-myc with one of the Ig loci is an early, invariant event that is mediated by B cell-specific DNA modification mechanisms. By contrast, for MM, dysregulation of c-myc apparently is caused principally by complex genomic rearrangements that occur during late stages of MM progression and do not involve B cell-specific DNA modification mechanisms.
Asunto(s)
Aberraciones Cromosómicas/genética , Regulación Neoplásica de la Expresión Génica/genética , Genes myc/genética , Mieloma Múltiple/genética , Trastornos de los Cromosomas , Pintura Cromosómica , Reordenamiento Génico , Humanos , Cadenas Pesadas de Inmunoglobulina/genética , Cadenas Ligeras de Inmunoglobulina/genética , Hibridación Fluorescente in Situ , Cariotipificación , ARN Mensajero/genética , Translocación Genética/genética , Células Tumorales CultivadasRESUMEN
Dysregulation of oncogenes by translocation to an IgH (14q32) or IgL (kappa, 2p11 or lambda, 22q11) locus is a frequent event in the pathogenesis of B-cell tumors. Translocations involving an IgH locus and a diverse but nonrandom array of chromosomal loci occur in most multiple myeloma (MM) tumors even though the translocations often are not detected by conventional cytogenetic analysis. In a continuing analysis of translocations in 21 MM lines, we show that the novel, karyotypically silent t(14;16)(q32.3;q23) translocation is present in 5 MM lines, with cloned breakpoints from 4 lines dispersed over an approximately 500-kb region centromeric to the c-maf proto-oncogene at 16q23. Another line has a t(16;22)(q23;q11), with the breakpoint telomeric to c-maf, so that the translocation breakpoints in these 6 lines bracket c-maf. Only these 6 lines overexpress c-maf mRNA. As predicted for dysregulation of c-maf by translocation, there is selective expression of one c-maf allele in 2 informative lines with translocations. This is the first human tumor in which the basic zipper c-maf transcription factor is shown to function as an oncogene.
Asunto(s)
Cromosomas Humanos Par 14 , Cromosomas Humanos Par 16 , Proteínas de Unión al ADN/genética , Cadenas Pesadas de Inmunoglobulina/genética , Mieloma Múltiple/genética , Proteínas Proto-Oncogénicas/genética , Translocación Genética , Secuencia de Aminoácidos , Cromosomas Artificiales de Levadura , Regulación Neoplásica de la Expresión Génica , Genes de Inmunoglobulinas , Humanos , Hibridación Fluorescente in Situ , Datos de Secuencia Molecular , Proto-Oncogenes Mas , Proteínas Proto-Oncogénicas c-maf , Células Tumorales CultivadasRESUMEN
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
Translocation of c-myc to IgH switch regions, or less frequently to one of the IgL loci, is essentially an invariant event in murine plasmacytomas. This results in dysregulation of c-myc, manifested by selective expression of the translocated allele. Human multiple myeloma (MM) has a similarly high incidence of translocations involving IgH switch regions, but c-myc is infrequently involved as a partner in these translocations. However, in screening a panel of 20 MM cell lines, we identified six lines containing two genetically distinguishable c-myc alleles. For these six informative lines (and the corresponding tumor for one line) there is selective expression of one c-myc allele despite the apparent absence of translocation, DNA rearrangement, or amplification involving c-myc. This result suggests frequent tumor specific cis-dysregulation of c-myc in MM by a presently unknown mechanism.
Asunto(s)
Genes myc , Mieloma Múltiple/genética , Alelos , Animales , ADN de Neoplasias/genética , Expresión Génica , Regulación Neoplásica de la Expresión Génica , Genes de Inmunoglobulinas , Humanos , Cadenas Pesadas de Inmunoglobulina/genética , Ratones , Reacción en Cadena de la Polimerasa , Translocación Genética , Células Tumorales CultivadasRESUMEN
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
Chromosomal translocations or DNA rearrangements affecting c-myc occur in almost all murine plasmacytoma and human Burkitt's lymphoma tumors and are associated with a high incidence of exon 2 missense mutations and selective expression of the affected allele. Screening nine multiple myeloma cell lines, we identified no exon 2 missense mutations but did identify two lines with single, silent mutations in exon 1 and exon 2, respectively. Each of these informative multiple myeloma cell lines selectively expresses only one c-myc allele despite the apparent absence of chromosomal translocations or DNA rearrangements affecting c-myc.
Asunto(s)
Alelos , Exones/genética , Regulación Neoplásica de la Expresión Génica , Genes myc , Mieloma Múltiple/genética , Mutación Puntual , Linfocitos B/metabolismo , Linfocitos B/virología , Linfoma de Burkitt/genética , Linfoma de Burkitt/patología , Línea Celular Transformada , Análisis Mutacional de ADN , ADN de Neoplasias/genética , Herpesvirus Humano 4 , Humanos , Mieloma Múltiple/patología , Reacción en Cadena de la Polimerasa , Polimorfismo Conformacional Retorcido-Simple , Células Tumorales CultivadasRESUMEN
Translocations involving the IgH locus at chromosomal locus 14q32.3 are a common event in many B-cell malignancies. The translocations, which generally occur into JH and switch regions, are mediated by errors in the two developmentally regulated, lymphocyte-specific pathways: VDJ-and switch-mediated recombination. Dysregulation of cyclin D1 by a t(11;14)(q13;q32) translocation occurs in most cases of mantle-cell lymphoma and in approximately 30% of multiple myeloma (MM) tumors in which a 14q32 translocation can be detected. We show here that in two of three myeloma lines that overexpress cyclin D1, there is an 11;14 translocation into a gamma switch region, suggesting an error in switch recombination. By contrast, 11;14 translocations in mantlecell lymphoma are invariably into or near a JH segment, suggesting an error in VDJ recombination. This is consistent with the fact that myeloma cells have undergone lgH switch recombination, whereas mantle-cell lymphoma cells generally have not.
Asunto(s)
Cromosomas Humanos Par 11/genética , Cromosomas Humanos Par 14/genética , Ciclinas/genética , Regulación Neoplásica de la Expresión Génica , Genes de Cambio , Cambio de Clase de Inmunoglobulina/genética , Inmunoglobulina G/genética , Cadenas Pesadas de Inmunoglobulina/genética , Mieloma Múltiple/genética , Proteínas de Mieloma/genética , Proteínas Oncogénicas/genética , Translocación Genética , Secuencia de Bases , Southern Blotting , Ciclina D1 , ADN Nucleotidiltransferasas/metabolismo , ADN de Neoplasias/genética , Reordenamiento Génico de Cadena Pesada de Linfocito B , Humanos , Linfoma de Células B/genética , Datos de Secuencia Molecular , Mieloma Múltiple/patología , Recombinación Genética , VDJ RecombinasasRESUMEN
The c-Myb protein is a transcription factor with an apparent but poorly defined role in hematopoietic cell growth and differentiation. The DNA binding and several transcriptional regulatory domains of the c-Myb protein have been defined by transient transfections into nonhematopoietic cell lines. Although the relationship between these domains and transformation has been studied, little is known about the function of these domains during hematopoietic maturation. Up-regulation of stably transfected c-myb in murine erythroleukemia (MEL) cells blocks terminal differentiation when MEL cells are induced to differentiate with N,N'-hexamethylene bisacetamide. To determine which functional domains of c-Myb are necessary and sufficient to block differentiation, mutated c-myb constructs under the control of a murine metallothionein promoter were transfected into C19 MEL cells, and stable clonal cell lines were established. The ability of Myb mutants to block differentiation paralleled their ability to transactivate transcription of a reporter gene containing Myb-responsive elements, by transient transfection into a lymphoid cell line. The smallest c-Myb mutant able to block differentiation consisted of the DNA binding domain juxtaposed to the transactivation domain. Therefore, the DNA binding domain and the transactivation domain are necessary and sufficient for c-Myb to block differentiation in MEL cells.
Asunto(s)
Diferenciación Celular/fisiología , Proteínas de Unión al ADN/metabolismo , Oncogenes , Proteínas Proto-Oncogénicas/metabolismo , Acetamidas/farmacología , Animales , Secuencia de Bases , Diferenciación Celular/efectos de los fármacos , Núcleo Celular/metabolismo , Virus de la Leucemia Murina de Friend/genética , Eliminación de Gen , Leucemia Eritroblástica Aguda , Ratones , Datos de Secuencia Molecular , Oligodesoxirribonucleótidos , Oligonucleótidos Antisentido , Proteínas Proto-Oncogénicas/genética , Proteínas Proto-Oncogénicas/aislamiento & purificación , Proteínas Proto-Oncogénicas c-myb , ARN Mensajero/genética , ARN Mensajero/aislamiento & purificación , ARN Mensajero/metabolismo , Mapeo Restrictivo , Activación Transcripcional , Transfección , Células Tumorales CultivadasRESUMEN
We have analyzed a murine plasmacytoma minus highly differentiated B lymphoma subtractive cDNA library and identified eight genes that are expressed in most plasmacytomas but at a much lower level, or not at all, in most B lymphomas. Four of the genes are markers of the terminal differentiation of B lymphocytes into plasma cells: placental alkaline phosphatase, also expressed in pre-B lymphomas xlr-3, a new X-linked member of the xlr multi-gene family EGP314, a pan-epithelial glycoprotein with sequence features of an adhesion molecule PC315, a gene that is up-regulated by IL6, but without obvious sequence homologies. Two of the genes are not clearly related to normal B cell differentiation, appearing to be associated with malignant transformation of plasma cells: PC326 is a new member of the beta-transducin mosaic protein gene family. It is an X-linked gene, expressed at a very low level in testis, but in no other normal tissue, including LPS- or IL6-induced plasma cells. It has a high level of expression (apparently dysregulated) in most (> 85%) mineral oil induced plasmacytomas. However the likelihood that PC326 is expressed decreases as the tumor latency decreases when different retroviral agents are used to accelerate mineral oil induced plasmacytomagenesis. This suggests that PC326 expression may be a late event in a multi-step process of tumorigenesis. PC251 a new member of the hematopoietic growth factor receptor family, most homologous to IL5R alpha.(ABSTRACT TRUNCATED AT 250 WORDS)