RESUMO
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.
Assuntos
Regulação Neoplásica da Expressão Gênica , Mieloma Múltiplo/genética , Mutação , Proteínas Tirosina Quinases , Receptores de Fatores de Crescimento de Fibroblastos/genética , Translocação Genética/genética , Northern Blotting , Southern Blotting , Cromossomos Humanos Par 14/genética , Cromossomos Humanos Par 4/genética , Sondas de DNA , Humanos , Immunoblotting , Hibridização in Situ Fluorescente , Cariotipagem , Dados de Sequência Molecular , Oncogenes/genética , Reação em Cadeia da Polimerase , RNA Mensageiro/metabolismo , Receptor Tipo 3 de Fator de Crescimento de Fibroblastos , Receptores de Fatores de Crescimento de Fibroblastos/biossíntese , Células Tumorais CultivadasRESUMO
Chromosomal hyperdiploidy is the defining genetic signature in 40-50% of myeloma (MM) patients. We characterize hyperdiploid-MM (H-MM) in terms of its clinical and prognostic features in a cohort of 220 H-MM patients entered into clinical trials. Hyperdiploid-myeloma is associated with male sex, kappa immunoglobulin subtype, symptomatic bone disease and better survival compared to nonhyperdiploid-MM (median overall survival 48 vs 35 months, log-rank P = 0.023), despite similar response to treatment. Among 108 H-MM cases with FISH studies for common genetic abnormalities, survival is negatively affected by the existence of immunoglobulin heavy chain (IgH) translocations, especially those involving unknown partners, while the presence of chromosome 13 deletion by FISH did not significantly affect survival (median overall survival 50 vs 47 months, log-rank P = 0.47). Hyperdiploid-myeloma is therefore a unique genetic subtype of MM associated with improved outcome with distinct clinical features. The existence of IgH translocations but not chromosome 13 deletion by FISH negatively impacts survival and may allow further risk stratification of this population of MM patients.
Assuntos
Deleção Cromossômica , Cromossomos Humanos Par 13/genética , Cromossomos Humanos Par 17/genética , Cadeias Pesadas de Imunoglobulinas/genética , Mieloma Múltiplo/genética , Poliploidia , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Aberrações Cromossômicas , Feminino , Seguimentos , Genes p53/genética , Humanos , Masculino , Pessoa de Meia-Idade , Mieloma Múltiplo/tratamento farmacológico , Prognóstico , Ensaios Clínicos Controlados Aleatórios como Assunto/estatística & dados numéricos , Estudos Retrospectivos , Taxa de Sobrevida , Translocação Genética , Resultado do TratamentoRESUMO
Myeloma is heterogeneous at the molecular level with subgroups of patients characterised by features of epigenetic dysregulation. Outcomes for myeloma patients have improved over the past few decades except for molecularly defined high-risk patients who continue to do badly. Novel therapeutic approaches are, therefore, required. A growing number of epigenetic inhibitors are now available including EZH2 inhibitors that are in early-stage clinical trials for treatment of haematological and other cancers with EZH2 mutations or in which overexpression has been correlated with poor outcomes. For the first time, we have identified and validated a robust and independent deleterious effect of high EZH2 expression on outcomes in myeloma patients. Using two chemically distinct small-molecule inhibitors, we demonstrate a reduction in myeloma cell proliferation with EZH2 inhibition, which leads to cell cycle arrest followed by apoptosis. This is mediated via upregulation of cyclin-dependent kinase inhibitors associated with removal of the inhibitory H3K27me3 mark at their gene loci. Our results suggest that EZH2 inhibition may be a potential therapeutic strategy for the treatment of myeloma and should be investigated in clinical studies.
Assuntos
Pontos de Checagem do Ciclo Celular/genética , Proteína Potenciadora do Homólogo 2 de Zeste/genética , Expressão Gênica , Mieloma Múltiplo/genética , Mieloma Múltiplo/mortalidade , Apoptose/genética , Biomarcadores , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/genética , Proteína Potenciadora do Homólogo 2 de Zeste/antagonistas & inibidores , Epigênese Genética , Perfilação da Expressão Gênica , Histonas/metabolismo , Humanos , Estimativa de Kaplan-Meier , Células-Tronco Mesenquimais/metabolismo , Mieloma Múltiplo/diagnóstico , Mieloma Múltiplo/terapia , Fenótipo , Prognóstico , Modelos de Riscos Proporcionais , RNA Mensageiro/genéticaRESUMO
Hyperdiploid and non-hyperdiploid multiple myeloma represents distinct biological entities characterized by different patterns of genetic changes. We sought to determine whether ploidy category (non-hyperdiploid versus hyperdiploid) remains stable over time from diagnosis to progression. Of the 43 patients studied (39 by flow cytometry DNA index and 4 by a FISH-based index), only five (12%) altered their ploidy status at progression. In three of these patients, the change may possibly be attributable to technical artifacts because of the low absolute change in DNA index. For those who retain their ploidy subtypes, the DNA index change minimally (3.75+/-4.87%). It would appear that the initiating genetic events underlying hyperdiploid and non-hyperdiploid MM that marks them out as distinct entities continue to dominate and persist during disease evolution and progression.
Assuntos
DNA de Neoplasias/genética , Mieloma Múltiplo/genética , Ploidias , DNA de Neoplasias/análise , Progressão da Doença , Feminino , Citometria de Fluxo , Humanos , Hibridização in Situ Fluorescente , Masculino , Mieloma Múltiplo/patologiaRESUMO
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.
Assuntos
Alelos , Éxons/genética , Regulação Neoplásica da Expressão Gênica , Genes myc , Mieloma Múltiplo/genética , Mutação Puntual , Linfócitos B/metabolismo , Linfócitos B/virologia , Linfoma de Burkitt/genética , Linfoma de Burkitt/patologia , Linhagem Celular Transformada , Análise Mutacional de DNA , DNA de Neoplasias/genética , Herpesvirus Humano 4 , Humanos , Mieloma Múltiplo/patologia , Reação em Cadeia da Polimerase , Polimorfismo Conformacional de Fita Simples , Células Tumorais CultivadasRESUMO
The role of endothelial progenitor cell (EPC)-mediated vasculogenesis in hematological malignancies is not well explored. Here, we showed that EPCs are mobilized from the bone marrow (BM) to the peripheral blood at early stages of multiple myeloma (MM); and recruited to MM cell-colonized BM niches. Using EPC-defective ID1+/- ID3-/- mice, we found that MM tumor progression is dependent on EPC trafficking. By performing RNA-sequencing studies, we confirmed that endothelial cells can enhance proliferation and favor cell-cycle progression only in MM clones that are smoldering-like and have dependency on endothelial cells for tumor growth. We further confirmed that angiogenic dependency occurs early and not late during tumor progression in MM. By using a VEGFR2 antibody with anti-vasculogenic activity, we demonstrated that early targeting of EPCs delays tumor progression, while using the same agent at late stages of tumor progression is ineffective. Thus, although there is significant angiogenesis in myeloma, the dependency of the tumor cells on EPCs and vasculogenesis may actually precede this step. Manipulating vasculogenesis at an early stage of disease may be examined in clinical trials in patients with smoldering MM, and other hematological malignancies with precursor conditions.
Assuntos
Mieloma Múltiplo/patologia , Neovascularização Patológica/tratamento farmacológico , Animais , Anticorpos/uso terapêutico , Medula Óssea , Movimento Celular , Células Clonais/patologia , Progressão da Doença , Células Endoteliais/patologia , Camundongos , Mieloma Múltiplo/irrigação sanguínea , Mieloma Múltiplo/tratamento farmacológico , Neovascularização Patológica/prevenção & controle , Prevenção Secundária , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/imunologiaRESUMO
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.
Assuntos
Genes myc , Mieloma Múltiplo/genética , Alelos , Animais , DNA de Neoplasias/genética , Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Genes de Imunoglobulinas , Humanos , Cadeias Pesadas de Imunoglobulinas/genética , Camundongos , Reação em Cadeia da Polimerase , Translocação Genética , Células Tumorais CultivadasRESUMO
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.
Assuntos
Cadeias Pesadas de Imunoglobulinas/genética , Mieloma Múltiplo/genética , Mieloma Múltiplo/imunologia , Translocação Genética , Animais , Cromossomos Humanos Par 14/genética , Cromossomos Humanos Par 21/genética , Cromossomos Humanos Par 8/genética , Genes de Imunoglobulinas , Genes myc , Humanos , Região de Troca de Imunoglobulinas/genética , Camundongos , Células Tumorais CultivadasRESUMO
Multiple myeloma (MM) is a tumor of indolent, bone marrow (BM) localized, isotype-switched plasma cells. Recently, the diagnostic criteria have been amended to include some patients who would previously have been diagnosed with ultra-high-risk smoldering MM and benefit from immediate treatment. Genetically it can be divided into tumors with different recurrent immunoglobulin heavy chain gene translocations (4p16, 11q13, 6p21, 16q23, 20q11) and tumors characterized by hyperdiploidy with multiple trisomies. Recent genomic studies have shown that almost half of untreated patients have a genetic rearrangements of the MYC locus that result in juxtaposition of ectopic super-enhancers adjacent to MYC, as well as somatic mutations that activate the RAS/MAPK pathway (NRAS, KRAS, BRAF, FGFR3). Mutations that result in constitutive activation of the NFkB pathway and that inactivate TP53, CDKN2C, KDM6A, FAM46C, and DIS3 are also recurrent. A major insight from these studies has been the recognition of the high degree of subclonal heterogeneity in MM, which is more frequent in patients with high-risk genetics. The subclones may alternate in dominance under alternating therapeutic pressure, a phenomenon known as 'clonal tides'. The identification of marked subclonal heterogeneity argues in those patients for the use of therapeutic strategies to maximize response, and long-term suppressive therapies to prevent tumor regrowth and development of additional subclones.
Assuntos
Mieloma Múltiplo/diagnóstico , Mieloma Múltiplo/genética , Translocação Genética , Trissomia , Rearranjo Gênico , Humanos , Modelos Genéticos , Mutação , Proteínas Proto-Oncogênicas c-myc/genética , Transdução de Sinais/genéticaRESUMO
The phosphatidylinositol 3'-kinase (PI3K) pathway is dysregulated in multiple myeloma (MM); we therefore tested a highly selective class I PI3K inhibitor, GDC-0941, for anti-myeloma activity. Functional and mechanistic studies were first performed in MM cell lines, then extended to primary MM patient samples cultured in vitro. GDC-0941 was then assessed as a single agent and in various combinations in myeloma tumor xenograft models. We show p110 α and ß are the predominant PI3K catalytic subunits in MM and that a highly selective class I PI3K inhibitor, GDC-0941, has robust activity as a single agent to induce cell cycle arrest and apoptosis of both MM cell lines and patient myeloma cells. Mechanistic studies revealed an induction of cell cycle arrest at G0/G1, with decreased phospho-FoxO1/3a levels, decreased cyclin D1 and c-myc expression, and an increase in the cell cycle inhibitor, p27kip. Induction of apoptosis correlated with increased expression of the pro-apoptotic BH3-only protein BIM, cleaved caspase 3 and cleaved poly (ADP-ribose) polymerase (PARP). In vitro, GDC-0941 synergized with dexamethasone (Dex) and lenalidomide (combination index values of 0.3-0.4 and 0.4-0.8, respectively); in vivo GDC-0941 has anti-myeloma activity and significantly increases the activity of the standard of care agents in several murine xenograft tumor models (additional tumor growth inhibition of 37-53% (Dex) and 22-72% (lenalidomide)). These data provide a clear therapeutic hypothesis for the inhibition of PI3K and provide a rationale for clinical development of GDC-0941 in myeloma.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Indazóis/farmacologia , Mieloma Múltiplo/tratamento farmacológico , Inibidores de Fosfoinositídeo-3 Quinase , Sulfonamidas/farmacologia , Animais , Apoptose/efeitos dos fármacos , Western Blotting , Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Classe I de Fosfatidilinositol 3-Quinases , Dexametasona/administração & dosagem , Feminino , Humanos , Indazóis/administração & dosagem , Concentração Inibidora 50 , Lenalidomida , Camundongos , Camundongos SCID , Mieloma Múltiplo/patologia , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Sulfonamidas/administração & dosagem , Talidomida/administração & dosagem , Talidomida/análogos & derivados , Carga Tumoral/genética , Ensaios Antitumorais Modelo de XenoenxertoAssuntos
Cromossomos Humanos Par 14 , Cromossomos Humanos Par 4 , Mieloma Múltiplo/genética , Translocação Genética , Células da Medula Óssea/metabolismo , Progressão da Doença , Evolução Molecular , Citometria de Fluxo , Humanos , Imuno-Histoquímica , Hibridização in Situ Fluorescente , Reação em Cadeia da Polimerase , Sensibilidade e Especificidade , Resultado do TratamentoRESUMO
Multiple myeloma (MM) is an incurable malignancy with an unmet need for innovative treatment options. Histone deacetylase inhibitors (HDACi) are a new class of anticancer agent that have demonstrated activity in hematological malignancies. Here, we investigated the efficacy and safety of HDACi (vorinostat, panobinostat, romidepsin) and novel combination therapies using in vitro human MM cell lines and in vivo preclinical screening utilizing syngeneic transplanted Vk*MYC MM. HDACi were combined with ABT-737, which targets the intrinsic apoptosis pathway, recombinant human tumour necrosis factor-related apoptosis-inducing ligand (rhTRAIL/MD5-1), that activates the extrinsic apoptosis pathway or the DNA methyl transferase inhibitor 5-azacytidine. We demonstrate that in vitro cell line-based studies provide some insight into drug activity and combination therapies that synergistically kill MM cells; however, they do not always predict in vivo preclinical efficacy or toxicity. Importantly, utilizing transplanted Vk*MYC MM, we report that panobinostat and 5-azacytidine synergize to prolong the survival of tumor-bearing mice. In contrast, combined HDACi/rhTRAIL-based strategies, while efficacious, demonstrated on-target dose-limiting toxicities that precluded prolonged treatment. Taken together, our studies provide evidence that the transplanted Vk*MYC model of MM is a useful screening tool for anti-MM drugs and should aid in the prioritization of novel drug testing in the clinic.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Azacitidina/uso terapêutico , Compostos de Bifenilo/uso terapêutico , Inibidores de Histona Desacetilases/uso terapêutico , Mieloma Múltiplo/tratamento farmacológico , Nitrofenóis/uso terapêutico , Sulfonamidas/uso terapêutico , Ligante Indutor de Apoptose Relacionado a TNF/uso terapêutico , Animais , Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Apoptose/efeitos dos fármacos , Azacitidina/farmacologia , Compostos de Bifenilo/farmacologia , Ensaios de Seleção de Medicamentos Antitumorais , Inibidores de Histona Desacetilases/farmacologia , Humanos , Ácidos Hidroxâmicos/farmacologia , Ácidos Hidroxâmicos/uso terapêutico , Indóis/farmacologia , Indóis/uso terapêutico , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Mieloma Múltiplo/metabolismo , Mieloma Múltiplo/patologia , Nitrofenóis/farmacologia , Panobinostat , Piperazinas/farmacologia , Piperazinas/uso terapêutico , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Proteínas Proto-Oncogênicas c-myc/metabolismo , Receptores de Morte Celular/metabolismo , Proteínas Recombinantes , Sulfonamidas/farmacologia , Ligante Indutor de Apoptose Relacionado a TNF/farmacologiaRESUMO
RNA interference screening identified XPO1 (exportin 1) among the 55 most vulnerable targets in multiple myeloma (MM). XPO1 encodes CRM1, a nuclear export protein. XPO1 expression increases with MM disease progression. Patients with MM have a higher expression of XPO1 compared with normal plasma cells (P<0.04) and to patients with monoclonal gammopathy of undetermined significance/smoldering MM (P<0.0001). The highest XPO1 level was found in human MM cell lines (HMCLs). A selective inhibitor of nuclear export compound KPT-276 specifically and irreversibly inhibits the nuclear export function of XPO1. The viability of 12 HMCLs treated with KTP-276 was significantly reduced. KPT-276 also actively induced apoptosis in primary MM patient samples. In gene expression analyses, two genes of probable relevance were dysregulated by KPT-276: cell division cycle 25 homolog A (CDC25A) and bromodomain-containing protein 4 (BRD4), both of which are associated with c-MYC pathway. Western blotting and reverse transcription-PCR confirm that c-MYC, CDC25A and BRD4 are all downregulated after treatment with KPT-276. KPT-276 reduced monoclonal spikes in the Vk*MYC transgenic MM mouse model, and inhibited tumor growth in a xenograft MM mouse model. A phase I clinical trial of an analog of KPT-276 is ongoing in hematological malignancies including MM.
Assuntos
Acrilamidas/farmacologia , Transporte Biológico/efeitos dos fármacos , Núcleo Celular/efeitos dos fármacos , Estudo de Associação Genômica Ampla , Carioferinas/genética , Mieloma Múltiplo/genética , Receptores Citoplasmáticos e Nucleares/genética , Tiazóis/farmacologia , Animais , Linhagem Celular Tumoral , Núcleo Celular/metabolismo , Perfilação da Expressão Gênica , Humanos , Carioferinas/efeitos dos fármacos , Camundongos , Interferência de RNA , Receptores Citoplasmáticos e Nucleares/efeitos dos fármacos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Ensaios Antitumorais Modelo de Xenoenxerto , Proteína Exportina 1Assuntos
Bortezomib/farmacologia , Ferro/metabolismo , Mieloma Múltiplo/tratamento farmacológico , Mieloma Múltiplo/metabolismo , Plasmócitos/efeitos dos fármacos , Plasmócitos/metabolismo , Animais , Morte Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Progressão da Doença , Humanos , Camundongos , Mieloma Múltiplo/patologia , Plasmócitos/patologiaRESUMO
Events mediating transformation from the pre-malignant monoclonal gammopathy of undetermined significance (MGUS) to multiple myeloma (MM) are unknown. We analyzed gene expression data sets generated on the Affymetrix U133 platform from 22 MGUS and 101 MM patients using gene-set enrichment analysis. Genes overexpressed in MM were enriched for cell cycle, proliferation and MYC activation gene sets. Upon dissecting the relationship between MYC and cell-cycle gene sets, we identified and validated an MYC activation signature dissociated from proliferation. Applying this signature, MYC is activated in 67% of myeloma, but not in MGUS. This was further confirmed by immunohistochemistry (IHC) using membrane CD138 and nuclear MYC double staining. We also showed that almost all tumors with RAS mutations expressed the MYC activation signature, and multiple mechanisms may be involved in activating MYC. MYC activation, whether assessed by gene-expression signature or IHC, is associated with hyperdiploid MM and shorter survival even in tumors that are not proliferative. Bortezomib treatment is able to overcome the survival disadvantage in patients with MYC activation.
Assuntos
Transformação Celular Neoplásica/genética , Gamopatia Monoclonal de Significância Indeterminada/genética , Mieloma Múltiplo/genética , Proteínas Proto-Oncogênicas c-myc/metabolismo , Ácidos Borônicos/uso terapêutico , Bortezomib , Ciclo Celular/genética , Perfilação da Expressão Gênica , Humanos , Gamopatia Monoclonal de Significância Indeterminada/patologia , Mieloma Múltiplo/patologia , Mutação , Proteínas Proto-Oncogênicas c-myc/genética , Pirazinas/uso terapêutico , Taxa de Sobrevida , Proteínas ras/genéticaRESUMO
Myeloma is a malignant proliferation of monoclonal plasma cells. Although morphologically similar, several subtypes of the disease have been identified at the genetic and molecular level. These genetic subtypes are associated with unique clinicopathological features and dissimilar outcome. At the top hierarchical level, myeloma can be divided into hyperdiploid and non-hyperdiploid subtypes. The latter is mainly composed of cases harboring IgH translocations, generally associated with more aggressive clinical features and shorter survival. The three main IgH translocations in myeloma are the t(11;14)(q13;q32), t(4;14)(p16;q32) and t(14;16)(q32;q23). Trisomies and a more indolent form of the disease characterize hyperdiploid myeloma. A number of genetic progression factors have been identified including deletions of chromosomes 13 and 17 and abnormalities of chromosome 1 (1p deletion and 1q amplification). Other key drivers of cell survival and proliferation have also been identified such as nuclear factor- B-activating mutations and other deregulation factors for the cyclin-dependent pathways regulators. Further understanding of the biological subtypes of the disease has come from the application of novel techniques such as gene expression profiling and array-based comparative genomic hybridization. The combination of data arising from these studies and that previously elucidated through other mechanisms allows for most myeloma cases to be classified under one of several genetic subtypes. This paper proposes a framework for the classification of myeloma subtypes and provides recommendations for genetic testing. This group proposes that genetic testing needs to be incorporated into daily clinical practice and also as an essential component of all ongoing and future clinical trials.
Assuntos
Testes Genéticos/métodos , Mieloma Múltiplo/classificação , Classificação , Análise Citogenética , Perfilação da Expressão Gênica , Humanos , Mieloma Múltiplo/genética , PrognósticoRESUMO
BACKGROUND: Chromosome translocations involving the immunoglobulin heavy chain gene (IgH) on 14q32 are a seminal event in the pathogenesis of many B-cell malignancies. Since myeloma is a post-germinal center tumor of mature, isotype switched plasma cells, we hypothesized that 14q32 translocations would usually involve IgH switch regions. MATERIALS AND METHODS: We analyzed a panel of 21 human myeloma cell lines using a Southern blot assay to detect illegitimate rearrangements involving the switch regions. We then cloned the breakpoints, developed probes for FISH analysis, and characterized the oncogenes dysregulated by the translocations. RESULTS: Only half of the cell lines demonstrated a 14q32 abnormality by conventional karyotypic analysis, but we were able to identify translocations involving IgH switch regions in 15 of 21 lines, including all of the lines in which a 14q32 translocations was not identified by conventional karyotypic analysis. Six cell lines have an Ig translocation involving 11q13 with overexpression of cyclin D1. Six cell lines have an Ig translocation involving 16q23 with overexpression of c-maf. Five lines have an Ig translocations involving 4p16 with overexpression of FGFR3 and a novel gene, MMSET. The 4p16 breakpoints occur within the 5' introns of MMSET, and are associated with IgH-MMSET hybrid mRNA transcripts. The remaining five cell lines have translocations involving other loci, including: 6p25 (MUM1), 8q24 (c-myc), and 21q22 (?AML1). CONCLUSIONS: Recurrent Ig translocations identify at least three distinct molecular subtypes of myeloma. Our long-term goal is to determine if there are phenotypic, prognostic and therapeutic differences associated with these molecular subtypes.
Assuntos
Cromossomos Humanos Par 11 , Cromossomos Humanos Par 13 , Cromossomos Humanos Par 16 , Imunoglobulinas/genética , Mieloma Múltiplo/genética , Translocação Genética , Southern Blotting , Humanos , Hibridização in Situ Fluorescente , Sensibilidade e EspecificidadeRESUMO
Oncogenes are often dysregulated in B cell tumors as a result of a reciprocal translocation involving an immunoglobulin locus. The translocations are caused by errors in two developmentally regulated DNA recombination processes: V(D)J and IgH switch recombination. Both processes share the property of joining discontinuous sequences from one chromosome and releasing intervening sequences as circles that are lost from progeny cells. Here we show that these intervening sequences may instead insert in the genome and that during productive IgH mu-epsilon switch recombination in U266 myeloma tumor cells, a portion of the excised IgH switch intervening sequences containing the 3' alpha-1 enhancer has inserted on chromosome 11q13, resulting in overexpression of the adjacent cyclin D1 oncogene.
Assuntos
Ciclina D1/genética , Regulação Neoplásica da Expressão Gênica/genética , Cadeias Pesadas de Imunoglobulinas/genética , Região de Troca de Imunoglobulinas/genética , Mieloma Múltiplo/genética , Sequência de Bases , Cromossomos Humanos Par 11/genética , Cromossomos Humanos Par 14/genética , Humanos , Hibridização in Situ Fluorescente , Dados de Sequência Molecular , Oncogenes/genética , Recombinação Genética/genética , Alinhamento de Sequência , Translocação Genética/genética , Células Tumorais CultivadasRESUMO
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.