RESUMO
Primary IGH translocations involving seven recurrent partner loci and oncogenes are present in about 40% of multiple myeloma tumors. Secondary IGH rearrangements, which occur in a smaller fraction of tumors, usually are complex structures, including insertions or translocations that can involve three chromosomes, and often with involvement of MYC. The main approach to detect IGH rearrangements is interphase-but sometimes metaphase-FISH strategies that use a telomeric variable region probe and a centromeric constant region/ Eα enhancer or 3' flanking probe to detect a separation of these two probes, or a fusion of these probes with probes located at nonrandom partner sites in the genome. We analyzed 18 myeloma cell lines for detection discrepancies among Vysis, Cytocell, and in-house IGH probe sets that hybridize with differing sequences in the IGH locus. There were no detection discrepancies for the three telomeric IGH probes, or for unrearranged IGH loci or primary IGH translocations using the centromeric IGH probes. However, the majority of complex IGH rearrangements had detection discrepancies among the three centromeric IGH probes.
Assuntos
Sondas de DNA/química , Rearranjo Gênico , Cadeias Pesadas de Imunoglobulinas/genética , Mieloma Múltiplo/genética , Linhagem Celular Tumoral , Cromossomos Humanos/genética , Humanos , Hibridização in Situ Fluorescente , Interfase , Mieloma Múltiplo/patologia , Mutagênese Insercional , Translocação GenéticaRESUMO
Multiple myeloma can be classified into hyperdiploid (HRD) (with 48-74 chromosomes) and non-hyperdiploid tumors (usually with immunoglobulin heavy chain translocations). The OH-2 human myeloma cell line (HMCL) retains the same HRD genotype as the primary tumor, with extra copies of chromosomes 3, 7, 15, 19, and 21. Both OH-2 and primary cells have a complex secondary translocation in which the IGK 3' enhancer is inserted between MYC and MAFB, resulting in dysregulation of both oncogenes. OH-2 provides a unique example of an HMCL and the corresponding primary tumor that are shown to share the same HRD genotype.
Assuntos
Genes myc , Cadeias Pesadas de Imunoglobulinas/genética , Cadeias kappa de Imunoglobulina/genética , Fator de Transcrição MafB/genética , Mieloma Múltiplo/genética , Translocação Genética , Linhagem Celular Tumoral , Diploide , Elementos Facilitadores Genéticos , Genótipo , Humanos , Hibridização in Situ Fluorescente , Cariotipagem , Mieloma Múltiplo/patologia , RNA Mensageiro/genética , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Translocations involving an MYC gene (c >> N >>L) are very late tumor progression events and provide a paradigm for secondary translocations in multiple myeloma. Using a combination of fluorescent in situ hybridization and comparative genomic hybridization arrays (aCGH), we have identified rearrangements of an MYC gene in 40 of 43 independent myeloma cell lines. A majority of MYC translocations involve an Ig locus (IgH > Iglambda >> Igkappa), but the breakpoints only infrequently occur near or within switch regions or V(D)J sequences. Surprisingly, about 40% of MYC translocations do not involve an Ig locus. The MYC translocations mostly are nonreciprocal translocations or insertions, often with the involvement of three chromosomes and sometimes with associated duplication, amplification, inversion, and other associated chromosomal abnormalities. High-density aCGH analyses should facilitate the cloning of MYC breakpoints, enabling the determination of their structures and perhaps elucidating how rearrangements not involving an Ig gene cause dysregulation of an MYC gene.
Assuntos
Cromossomos Humanos Par 14/genética , Cromossomos Humanos Par 8/genética , Genes myc/genética , Mieloma Múltiplo/genética , Translocação Genética , Perfilação da Expressão Gênica , Rearranjo Gênico/genética , Genes de Cadeia Pesada de Imunoglobulina , Humanos , Cadeias Leves de Imunoglobulina , Hibridização in Situ Fluorescente , Cariotipagem , Hibridização de Ácido Nucleico , Células Tumorais CultivadasRESUMO
The pathogenesis of multiple myeloma (MM) is thought to involve at least two pathways, which generate hyperdiploid (HRD) or nonhyperdiploid (NHRD) tumors, respectively. Apart from chromosome content, the two pathways are distinguished by five primary immunoglobulin heavy chain (IGH) rearrangements (4p16, FGFR3, and MMSET; 6p21, CCND3; 11q13, CCND1; 16q23, MAF; 20q12, MAFB) that are present mainly in NHRD tumors. To determine the prevalence and structures of IGH, immunoglobulin (IG) light chain, and MYC genomic rearrangements in MM, we have done comprehensive metaphase fluorescent in situ hybridization analyses on 48 advanced MM tumors and 47 MM cell lines. As expected, the prevalence of the five primary IGH rearrangements was nearly 70% in NHRD tumors, but only 12% in HRD tumors. However, IGH rearrangements not involving one of the five primary partners, and IG light chain rearrangements, have a similar prevalence in HRD and NHRD tumors. In addition, MYC rearrangements, which are thought to be late progression events that sometimes do not involve an IG heavy or light chain locus, also have a similar prevalence in HRD and NHRD tumors. In contrast to the primary IGH rearrangements, which usually are simple balanced translocations, these other IG rearrangements usually have complex structures, as previously described for MYC rearrangements in MM. We conclude that IG light chain and MYC rearrangements, as well as secondary IGH rearrangements, make similar contributions to the progression of both HRD and NHRD MM tumors.
Assuntos
Rearranjo Gênico , Genes de Cadeia Pesada de Imunoglobulina/genética , Genes myc/genética , Cadeias Leves de Imunoglobulina/genética , Mieloma Múltiplo/genética , Cromossomos Humanos Par 11/genética , Cromossomos Humanos Par 14/genética , Diploide , Humanos , Hibridização in Situ Fluorescente , Cariotipagem , Mieloma Múltiplo/patologia , Translocação Genética , Células Tumorais CultivadasRESUMO
Mechanisms of constitutive NF-kappaB signaling in multiple myeloma are unknown. An inhibitor of IkappaB kinase beta (IKKbeta) targeting the classical NF-kappaB pathway was lethal to many myeloma cell lines. Several cell lines had elevated expression of NIK due to genomic alterations or protein stabilization, while others had inactivating mutations of TRAF3; both kinds of abnormality triggered the classical and alternative NF-kappaB pathways. A majority of primary myeloma patient samples and cell lines had elevated NF-kappaB target gene expression, often associated with genetic or epigenetic alteration of NIK, TRAF3, CYLD, BIRC2/BIRC3, CD40, NFKB1, or NFKB2. These data demonstrate that addiction to the NF-kappaB pathway is frequent in myeloma and suggest that IKKbeta inhibitors hold promise for the treatment of this disease.
Assuntos
Regulação Neoplásica da Expressão Gênica , Mieloma Múltiplo/genética , NF-kappa B/genética , Transdução de Sinais , Proteína 3 com Repetições IAP de Baculovírus , Western Blotting , Antígenos CD40/genética , Antígenos CD40/metabolismo , Células Cultivadas , Enzima Desubiquitinante CYLD , Ativação Enzimática , Inibidores Enzimáticos/farmacologia , Ensaio de Imunoadsorção Enzimática , Perfilação da Expressão Gênica , Humanos , Quinase I-kappa B/antagonistas & inibidores , Quinase I-kappa B/genética , Quinase I-kappa B/metabolismo , Proteínas Inibidoras de Apoptose/genética , Proteínas Inibidoras de Apoptose/metabolismo , Mieloma Múltiplo/metabolismo , Mieloma Múltiplo/patologia , NF-kappa B/antagonistas & inibidores , NF-kappa B/metabolismo , Subunidade p50 de NF-kappa B/genética , Subunidade p50 de NF-kappa B/metabolismo , Subunidade p52 de NF-kappa B/genética , Subunidade p52 de NF-kappa B/metabolismo , Plasmídeos , Reação em Cadeia da Polimerase , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Fator 3 Associado a Receptor de TNF/genética , Fator 3 Associado a Receptor de TNF/metabolismo , Transfecção , Translocação Genética , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismo , Ubiquitina-Proteína Ligases , Quinase Induzida por NF-kappaBRESUMO
Multiple myeloma (MM) is a malignant post-germinal center tumor of somatically-mutated, isotype-switched plasma cells that accumulate in the bone marrow. It often is preceded by a stable pre-malignant tumor called monoclonal gammopathy of undetermined significance (MGUS), which can sporadically progress to MM. Five recurrent primary translocations involving the immunoglobulin heavy chain (IgH) locus on chromosome 14q32 have been identified in MGUS and MM tumors. The five partner loci include 11q13, 6p21, 4p16, 16q23, and 20q12, with corresponding dysregulation of CYCLIN D1, CYCLIN D3, FGFR3/MMSET, c-MAF, and MAFB, respectively, by strong enhancers in the IgH locus. The five recurrent translocations, which are present in 40% of MM tumors, typically are simple reciprocal translocations, mostly having breakpoints within or near IgH switch regions but sometimes within or near VDJ or JH sequences. It is thought that these translocations are caused by aberrant IgH switch recombination, and possibly by aberrant somatic hypermutation in germinal center B cells, thus providing an early and perhaps initiating event in transformation. A MYC gene is dysregulated by complex translocations and insertions as a very late event during the progression of MM tumors. Since the IgH switch recombination and somatic hypermutation mechanism are turned off in plasma cells and plasma cell tumors, the MYC rearrangements are thought to be mediated by unknown mechanisms that contribute to structural genomic instability in all kinds of tumors. These rearrangements, which often but not always juxtapose MYC near one of the strong immunoglobulin enhancers, provide a paradigm for secondary translocations. It is hypothesized that secondary translocations not involving a MYC gene can occur at any stage of tumorigenesis, including in pre-malignant MGUS tumor cells.
Assuntos
Cromossomos Humanos Par 14 , Genes de Cadeia Pesada de Imunoglobulina/genética , Genes myc , Mieloma Múltiplo/genética , Translocação Genética , Linfoma de Burkitt/genética , Quebra Cromossômica , Humanos , Imunoglobulinas/genética , Linfoma de Células B/genética , Modelos Genéticos , Plasmocitoma/genéticaRESUMO
We report on a rapidly fatal case of acute plasmablastic leukemia in a 72-year-old male from The Ukraine, who was 70 km away from Chernobyl at the time of the atomic accident in 1986. Spectral karyotyping and fluorescence in situ hybridization (FISH) studies of a bone marrow sample obtained at diagnosis revealed a hypodiploid karyotype with 45 chromosomes and two novel complex rearrangements, der(8)t(8;20)(p11.2;p?12) and der(14)t(8;14)(p?;p11.2)t(11;14)(q13;q32), with juxtaposition of CH (constant region of IgH) sequences to the oncogene CCND1 (translocated to 14q32). FISH analysis demonstrated that the CH on the der(14) was duplicated.
