RESUMO
Numerous strategies have been proposed to specifically inhibit telomerase (human telomerase reverse transcriptase (hTERT)) but to date only a few are clinically relevant in anticancer therapy. Recently, we have shown that long-term treatment with all-trans retinoic acid (ATRA), a compound clinically approved for differentiation therapy of acute promyelocytic leukemia (APL), represses hTERT in differentiation-resistant APL cell lines leading to telomere shortening and death. This signaling requires the co-activation of the retinoic acid receptor alpha (RARalpha) and the retinoic X receptor (RXR). In contrast to differentiation-therapy, which is only successful in this subtype of leukemia, the telomerase-targeted pathway could also be of use in non-APL. Here, we demonstrate that repression of hTERT occurs in fresh blasts cells from patients with myeloid leukemias of various subtypes exposed ex vivo to ATRA or synthetic retinoids. These results support the idea that, by hTERT targeting, retinoids can induce telomere shortening and cell death and their integration in therapy protocols for myeloid leukemias refractory to maturation should be considered.
Assuntos
Antineoplásicos/farmacologia , Proteínas de Ligação a DNA/antagonistas & inibidores , Leucemia Mieloide/tratamento farmacológico , Leucemia Promielocítica Aguda/tratamento farmacológico , Retinoides/farmacologia , Telomerase/antagonistas & inibidores , Adulto , Idoso , Idoso de 80 Anos ou mais , Morte Celular/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Proteínas de Ligação a DNA/genética , Feminino , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Regulação Leucêmica da Expressão Gênica/efeitos dos fármacos , Humanos , Leucemia Mieloide/genética , Leucemia Mieloide/metabolismo , Masculino , Pessoa de Meia-Idade , RNA Mensageiro/efeitos dos fármacos , RNA Mensageiro/genética , Relação Estrutura-Atividade , Telomerase/genética , Telômero/efeitos dos fármacos , Telômero/genética , Resultado do Tratamento , Células Tumorais CultivadasRESUMO
Telomeres are located at the ends of eukaryotic chromosomes. Human telomerase, a cellular reverse transcriptase, is a ribonucleoprotein enzyme that catalyzes the synthesis and extension of telomeric DNA. It is composed of at least, a template RNA component (hTR; human Telomerase RNA) and a catalytic subunit, the telomerase reverse transcriptase (hTERT). The absence of telomerase is associated with telomere shortening and aging of somatic cells, while high telomerase activity is observed in over 85% of human cancer cells, strongly indicating its key role during tumorigenesis. Several details regarding telomere structure and telomerase regulation have already been elucidated, providing new targets for therapeutic exploitation. Further support for anti-telomerase approaches comes from recent studies indicating that telomerase is endowed of additional functions in the control of growth and survival of tumor cells that do not depend only on the ability of this enzyme to maintain telomere length. This observation suggests that inhibiting telomerase or its synthesis may have additional anti-proliferative and apoptosis inducing effect, independently of the reduction of telomere length during cell divisions. This article reviews the basic information about the biology of telomeres and telomerase and attempts to present various approaches that are currently under investigation to inhibit its expression and its activity. We summarize herein distinct anti-telomerase approaches like antisense strategies, reverse transcriptase inhibitors, and G-quadruplex interacting agents, and also review molecules targeting hTERT expression, such as retinoids and evaluate them for their therapeutic potential. "They conceive a certain theory, and everything has to fit into that theory. If one little fact will not fit it, they throw it aside. But it is always the facts that will not fit in that are significant". "Death on the Nile". Agatha Christie.
Assuntos
Antineoplásicos/farmacologia , Inibidores Enzimáticos/farmacologia , Neoplasias/tratamento farmacológico , Telomerase/antagonistas & inibidores , Telômero/efeitos dos fármacos , Animais , Humanos , Neoplasias/patologia , Telômero/químicaRESUMO
Acute promyelocytic leukemia (APL) is efficiently treated with a cell differentiation inducer, all-trans retinoic acid (ATRA). However, a significant percentage of patients still develop resistance to this treatment. Recently, arsenic trioxide (As2O3), alone or in combination with ATRA, has been identified as an alternative therapy in patients with both ATRA-sensitive and ATRA-resistant APL. Previous investigations restricted the mechanism of this synergism to the modulation and/or degradation of PML-RARalpha oncoprotein through distinct pathways. In this study, using several ATRA maturation-resistant APL cell lines, we demonstrate in vitro that the success of ATRA/As2O3 treatment in APL pathology can be explained, at least in part, by a synergistic effect of these two drugs in triggering downregulation of telomerase efficient enough to cause telomere shortening and subsequent cell death. Such long-term low-dose combinatorial therapy strategies, developed also to avoid acute side effects, reinforce the notion that the antitelomerase strategy, based on a combination of active agents, should now be considered and evaluated not only in APL but also in other malignancies.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Apoptose/efeitos dos fármacos , Proteínas de Ligação a DNA/metabolismo , Resistencia a Medicamentos Antineoplásicos , Leucemia Promielocítica Aguda/tratamento farmacológico , Telomerase/metabolismo , Trióxido de Arsênio , Arsenicais/administração & dosagem , Humanos , Leucemia Promielocítica Aguda/enzimologia , Leucemia Promielocítica Aguda/patologia , Proteínas de Neoplasias/metabolismo , Proteínas de Fusão Oncogênica/metabolismo , Óxidos/administração & dosagem , Indução de Remissão , Telômero/metabolismo , Tretinoína/administração & dosagem , Células Tumorais CultivadasRESUMO
We previously derived, from a nonmalignant clonal line of rat myogenic cells (L6 alpha 1), two sublines which have lost the capacity to differentiate, the M4 cell of low malignancy and the RMS4 cell of high malignancy. In the present study it is shown that 14 of 15 protooncogenes analyzed exhibit detectable levels of transcripts during L6 alpha 1 cell proliferation. When L6 alpha 1 cells from myotubes, the levels of c-abl, c-myb, and c-Ha-ras transcripts remain unchanged, the level of c-N-ras RNA is augmented, the level of c-erbB RNA is markedly reduced, and all other c-onc transcripts (c-erbA, c-sis, c-src, c-fes, c-fms, c-fos, c-myc, c-Ki-ras, and the putative tyrosine kinase transcript of the c-fgr gene) become hardly, if at all, detectable. Surprisingly, when the three cell types are growing at similar rates only, one protooncogene (c-mos) is not expressed at detectable levels in L6 alpha 1, two others (c-fos, c-erbA) are not expressed in M4 or in RMS4, and three additional ones (c-erbB, c-sis, c-src) are expressed in M4 but not in RMS4. Moreover the level of c-fes RNAs is markedly lower in RMS4 than in M4 or L6 alpha 1. By contrast, the level of two c-Ki-ras 5.4- and 2.2-kilobase transcripts is lower in M4 and L6 alpha 1 than in RMS4, and the latter contains another abundant c-Ki-ras 3.8-kilobase transcript which is hardly detectable in M4 and not at all in L6 alpha 1. These data suggest an activation of the c-Ki-ras gene in the malignant myoblasts and some relationship between the progression of malignancy and inactivation of certain other c-onc genes.
Assuntos
Transformação Celular Neoplásica , Músculos/metabolismo , Proto-Oncogenes , Actinas/genética , Animais , Diferenciação Celular , Transformação Celular Neoplásica/metabolismo , Transformação Celular Neoplásica/patologia , Células Cultivadas , RNA/análise , Ratos , Transcrição GênicaRESUMO
Two malignant sublines, M4 and RMS4 , were previously derived from the recloned L6 line of rat myogenic cells. Comparative studies in tissue culture and inoculation into suckling rats indicated that M4 cells and RMS4 cells may be considered as low-malignant and high-malignant cells, respectively, while L6 cells are not malignant. In the present work, we used extracts from L6 cells, M4 cells, and RMS4 cells collected during the period of exponential growth, to compare their polyadenylic acid-containing messenger RNA (mRNA) populations and the corresponding cell-free translation products. Analysis of the hybridization kinetics between radioactive complementary DNA and homologous or heterologous cellular RNAs indicated that L6 cells contained about 28,000 distinct polyadenylic acid-containing mRNA sequences of 1.8 kilobases each, of which 2,000 to 2,500 and 4,000 to 5,000 were missing (or at least were very infrequent) in M4 cells and RMS4 cells, respectively. Using a minor fraction of the RMS4 cell complementary DNAs, partially purified through repeated complementary DNA-RNA hybridization cycles, it was further shown that RMS4 cells contained at least 700 to 800 distinct mRNA species, mainly belonging to the class of low abundance, which appeared to be absent in L6 cells. Most of these mRNA species were also found with a lower frequency in M4 cells. Bidimensional analysis of the cell-free translation products directed by polyadenylic acid-containing mRNA revealed some remarkable differences, in particular the synthesis in a RMS4 cell extract of at least three major polypeptides, possibly related either to the neoplastic process itself or to the stage of malignant transformation.
Assuntos
Transformação Celular Neoplásica , Genes , Músculos/fisiologia , Oncogenes , Biossíntese de Proteínas , Transcrição Gênica , Animais , Linhagem Celular , Células Clonais , Peso Molecular , Proteínas de Neoplasias/isolamento & purificação , Hibridização de Ácido Nucleico , RNA Mensageiro/genética , RatosRESUMO
Sensitivity of tumor cells to anticancer therapy depends on the ability of the drug to induce apoptosis. However, multiple signaling pathways control this induction and thus determine this sensitivity. We report here that staurosporine, a well known inducer of apoptosis in a wide range of cell lines, displays distinct ability to trigger apoptosis in two different L1210 sublines (termed L1210/S and L1210/0). Staurosporine treatment resulted in an early cell death (within 3 h) in L1210/S cells, while in L1210/0 cells, death occurred only after 12 h. In both instances, death occurred by apoptosis. A broad spectrum caspase inhibitor, Z-VAD-fmk, blocked early apoptosis in L1210/S cells but did not confer any protection on late apoptosis in L1210/0 cells. Protection by Z-VAD-fmk observed in L1210/S cells was not lasting and unmasked a secondary process of cell death that also exhibited characteristics of apoptosis. Thus, staurosporine induces apoptotic cell death through at least two redundant parallel pathways. These two pathways normally coexist in L1210/S cells. However, the early cell death mechanism depending on caspase activation disguises the late caspase-independent apoptotic process. Staurosporine-induced apoptosis in L1210/0 cells develops only by the caspase-independent mechanism due to a general defect in caspase activation.
Assuntos
Apoptose/efeitos dos fármacos , Caspases/fisiologia , Estaurosporina/farmacologia , Clorometilcetonas de Aminoácidos/farmacologia , Animais , Apoptose/fisiologia , Caspases/biossíntese , Caspases/genética , Inibidores de Cisteína Proteinase/farmacologia , Impressões Digitais de DNA , DNA de Neoplasias/análise , Ativação Enzimática/efeitos dos fármacos , Indução Enzimática/efeitos dos fármacos , Leucemia L1210/patologia , Camundongos , Camundongos Endogâmicos DBA , Modelos Biológicos , Proteínas de Neoplasias/antagonistas & inibidores , Proteínas de Neoplasias/biossíntese , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/fisiologia , Células Tumorais CultivadasRESUMO
Two rearrangements affecting the same allele of the BCL2 gene were characterized by molecular analysis of an untreated follicular lymphoma. The first rearrangement interested the major breakpoint region (mbr) on chromosome 18 and a JH segment on chromosome 14. The other one was located at the 5' end of the BCL2 gene, in the so called variant cluster region (vcr), and consisted of a series of deletions that removed part of a DNA region where initiation of transcription normally occurs. Interestingly, both rearrangements involved the same BCL2 allele. The simultaneous presence of mbr (or mcr) translocations and of minor rearrangements in vcr has been previously suggested by restriction map analysis in a significant number of follicular lymphomas. The significance of these abnormalities on the oncogenic process is discussed.
Assuntos
Deleção de Genes , Rearranjo Gênico , Linfoma Folicular/genética , Oncogenes , Proteínas Proto-Oncogênicas/genética , Translocação Genética , Alelos , Sequência de Bases , Humanos , Dados de Sequência Molecular , Proteínas Proto-Oncogênicas c-bcl-2RESUMO
We have examined three cases of human lymphoma bearing a t(2;18)(p11;q21) chromosome translocation. The bcl-2 gene appeared to be rearranged in all three cases and breakpoints were clustered in the 5' flanking region of the gene. In all three cases, bcl-2 was juxtaposed to J segments of the Ig kappa gene. This juxtaposition of the bcl-2 and Ig kappa genes is very similar to the variant chromosome translocations of Burkitt lymphoma that juxtapose the c-myc locus to IgL genes.
Assuntos
Cromossomos Humanos Par 18 , Cromossomos Humanos Par 2 , Cadeias kappa de Imunoglobulina/genética , Linfoma Folicular/genética , Proteínas Proto-Oncogênicas/genética , Translocação Genética , Adulto , Southern Blotting , Sondas de DNA , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Proteínas Proto-Oncogênicas c-bcl-2RESUMO
The IPC-81 myeloid leukaemia cells undergo apoptosis rapidly after cAMP stimulation (6 h) and cell death is prevented by early over-expression of the cAMP-inducible transcription repressor ICER, that blocks cAMP-dependent nuclear signalling. Therefore, the expression of specific genes controlled by CRE-containing promoters is likely to determine cell fate. We now show that cAMP-induced cell death also is abrogated by the over-expression of the anti-apoptotic gene, Bcl-2. Contrary to ICER, Bcl-2 does not affect cAMP-signalling and allows the analysis of cAMP responses in death rescued cells. The Bcl-2 transfected cells treated with 8-CPT-cAMP were growth-arrested and thereafter cells embarked in granulocytic differentiation, with no additional stimulation. Neutrophilic polynuclear granulocytes benefited from a long life span in G0-G1 and remained functional (phagocytosis). This work demonstrates that, using anti-apoptosis regulators, 'death signals' could be exploited to trigger distinct biological responses. Indeed, cAMP signal can trigger several simultaneously developing biological programs, in the same cell, i.e., growth regulation, apoptosis and differentiation. This cell system should prove useful to determine how a tumour cell can be re-programmed for either apoptosis or functional maturation by physiological signals.
Assuntos
Apoptose , Diferenciação Celular , Núcleo Celular/metabolismo , AMP Cíclico/análogos & derivados , AMP Cíclico/farmacologia , Granulócitos/fisiologia , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Animais , Ciclo Celular/fisiologia , Fragmentação do DNA , Inibidores Enzimáticos/farmacologia , Citometria de Fluxo , Regulação da Expressão Gênica , Granulócitos/citologia , Proteínas Proto-Oncogênicas c-bcl-2/genética , Ratos , Transdução de Sinais , Tionucleotídeos/farmacologia , Transfecção , Células Tumorais CultivadasRESUMO
Molecular studies have recently demonstrated that the E2A transcription factor gene was consistently located on chromosome 19 at the breakpoint of the 1;19(q23;p13) translocation, which characterizes a number of leukemias harboring a pre-B cell phenotype. Using a specific E2A gene probe spanning the DNA binding and dimerization domain obtained by PCR methodology, we were able to detect the rearrangement of the E2A gene in four cases (three patients and one cell line) of pre-B acute lymphoblastic leukemia with t(1;19) translocation.
Assuntos
Sondas de DNA , Rearranjo Gênico , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Fatores de Transcrição/genética , Adulto , Sequência de Bases , Linhagem Celular , Criança , Pré-Escolar , Cromossomos Humanos Par 19 , Feminino , Humanos , Cariotipagem , Masculino , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Leucemia-Linfoma Linfoblástico de Células Precursoras/classificação , Translocação GenéticaRESUMO
The cellular prion protein (PrPc) is a sialoglycoprotein involved in the pathogenesis of prion diseases. It has been identified at the plasma membrane of several cell types. All-trans retinoic acid (ATRA) is known to induce differentiation of human leukemia cell lines in vitro. PrPc messenger ribonucleic acid (mRNA) and protein are down-regulated upon ATRA-induced differentiation of HL60 cells. In this report, we have investigated the regulation of PrPc mRNA and protein expression during ATRA-treatment of maturation-sensitive (NB4) and -resistant (NB4-R1 and NB4-R2) cell lines. In ATRA-induced maturation of NB4 cells, down-regulation of PrPc mRNA and protein were observed. We also show that down-regulation of PrPc mRNA is dependent on protein synthesis. Moreover, the same down-regulation of prion protein by ATRA was observed at the surface of maturation-resistant, ATRA-responsive NB4-R1 cells. In contrast, the maturation-resistant and ATRA-unresponsive NB4-R2 subline showed no variation in membrane prion protein expression. These results demonstrate a dissociation between the regulation of prion protein expression by ATRA and the process of granulocyte maturation. We propose that retinoids should be investigated further as a preventive strategy to slow down prion disease progression.
Assuntos
Granulócitos/citologia , Proteínas PrPC/metabolismo , Tretinoína/farmacologia , Diferenciação Celular , Relação Dose-Resposta a Droga , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/genética , Humanos , Cinética , Leucemia/patologia , Proteínas de Membrana/efeitos dos fármacos , Proteínas de Membrana/metabolismo , Proteínas PrPC/efeitos dos fármacos , Proteínas PrPC/genética , RNA Mensageiro/efeitos dos fármacos , RNA Mensageiro/metabolismo , Células Tumorais CultivadasRESUMO
Translocation t(3;22)(q27;q11) has recently been recognized as a recurrent abnormality in non-Hodgkin's malignant lymphoma (NHL). A new gene, LAZ3, has been shown to be involved in NHL with 3q27 rearrangement. Two patients with B-cell NHL were studied by chromosome painting and Southern blot analysis. Fluorescence in situ hybridization to metaphase chromosomes was shown to be an easy way to detect the chromosomal abnormality even in metaphase cells with poorly defined chromosomes. The gene LAZ3 was rearranged in one patient in the 'major translocation cluster region'. The comigration of rearranged LAZ3 and of IGL bands suggests that the translocation resulted in the juxtaposition of the two genes. This juxtaposition makes possible a potential deregulation of the LAZ3 gene expression, as previously shown for the MYC and BCL2 genes in Burkitt and follicular lymphoma translocations.
Assuntos
Cromossomos Humanos Par 22 , Cromossomos Humanos Par 3 , Linfoma não Hodgkin/genética , Translocação Genética , Idoso , Southern Blotting , Mapeamento Cromossômico , Feminino , Rearranjo Gênico , Genes Neoplásicos , Humanos , Hibridização in Situ Fluorescente , Linfoma de Células B/genética , Linfoma Folicular/genética , Pessoa de Meia-Idade , Dedos de Zinco/genéticaRESUMO
A child with acute myelomonocytic leukemia, bone marrow eosinophilia and inv(16) received first-line therapy including etoposide (VP-16). Cytopenia and monocytosis appeared 7 months after complete remission while the child was treated with maintenance chemotherapy. Blood abnormalities persisted after discontinuation of treatment. Nine months after complete remission, t(11;11)(q13;q23) and HRX rearrangement were detected. Five months later, overt leukemia of monocytic type occurred. The responsibility of VP-16 therapy in this treatment-related acute myelocytic leukemia is discussed.
Assuntos
Cromossomos Humanos Par 11 , Proteínas de Ligação a DNA/genética , Etoposídeo/efeitos adversos , Rearranjo Gênico , Leucemia Monocítica Aguda/genética , Leucemia Mielomonocítica Aguda/tratamento farmacológico , Segunda Neoplasia Primária/genética , Proto-Oncogenes , Fatores de Transcrição , Translocação Genética , Adolescente , Southern Blotting , Feminino , Histona-Lisina N-Metiltransferase , Humanos , Hibridização in Situ Fluorescente , Cariotipagem , Leucemia Monocítica Aguda/induzido quimicamente , Proteína de Leucina Linfoide-Mieloide , Segunda Neoplasia Primária/induzido quimicamenteRESUMO
The p11 band of the short arm of chromosome 9 is involved in various cytogenetic alterations occurring in several malignant diseases. Using probes isolated from the 9p11 band in the study of a case of alpha-heavy-chain disease (MAL) with t(9;14)(p11;q32), we studied the DNA from seven malignant cell samples, including four cases of acute lymphoblastic leukemia with tdic(9;12)(p11;p12). Using pulsed-field electrophoresis analysis we demonstrated that the breakpoints were 3-300 kb distant from the original MAL breakpoint without clustering within the subset of leukemias with the tdic(9;12).
Assuntos
Aberrações Cromossômicas , Fragilidade Cromossômica , Cromossomos Humanos Par 9 , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Mapeamento Cromossômico , Cromossomos Humanos Par 12 , Cromossomos Humanos Par 14 , Eletroforese/métodos , Doença das Cadeias Pesadas/genética , Humanos , Cadeias alfa de Imunoglobulina , Leucemia-Linfoma de Células T do Adulto/genética , Translocação GenéticaRESUMO
Rearrangements of the AML-1 gene on chromosome 21 as well as transcriptional expression of AML-1-ETO fusion gene were studied in 35 leukemic patients with t(8;21)(q22;q22). A panel of probes generated from the AML-1 gene regions flanking the breakpoint on chromosome 21 allowed us to detect the rearrangement in 24 out of 29 patients. A specific nested reverse transcriptase/polymerase chain reaction (RT/PCR) was developed to detect the t(8;21), either at diagnosis or as minimal residual disease. PCR amplification products were obtained in ten out of 11 patients investigated, and the sensitivity of the reaction was estimated to be between 1 x 10(4) and 1 x 10(-5) cell. An AML-1 rearrangement was also detected in one patient with 8q- and only one chromosome 21, but without 21q+. This indicated that the molecular rearrangement of the der(8) chromosome is more important than the reciprocal one in the malignant process.
Assuntos
Cromossomos Humanos Par 21 , Cromossomos Humanos Par 8 , Expressão Gênica , Rearranjo Gênico , Leucemia Mieloide Aguda/genética , Translocação Genética , Adolescente , Adulto , Idoso , Sequência de Bases , Biomarcadores Tumorais/análise , Criança , Pré-Escolar , Mapeamento Cromossômico , Clonagem Molecular , Feminino , Marcadores Genéticos , Humanos , Íntrons , Leucemia Mieloide Aguda/diagnóstico , Masculino , Pessoa de Meia-Idade , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , RNA Neoplásico/análise , DNA Polimerase Dirigida por RNA , Transcrição GênicaRESUMO
The MLL gene, located on chromosome band 11q23 is fused to different partner genes as a result of various chromosomal translocations in hematopoietic malignancies. A t(1;11) (q21;q23) resulting in a MLL-AF1q fusion gene has previously been reported. Cytogenetic studies on six cases are reported, including one three-way translocation. FISH analysis using a YAC encompassing the MLL gene and a YAC encompassing the AF1q locus showed splitting in three cases and two patients, respectively. PCR analysis of two cases confirmed that AF1q is specifically associated with t(1;11)(q21;q23). The MLL-AF1q fusion mRNA was similar to that previously described in one case and involved MLL exon 7 in the other. This study confirms the specific involvement of AF1q in t(1;11) (q21;q23)-positive acute leukemia with monocytic involvement.
Assuntos
Fusão Gênica Artificial , Cromossomos Humanos Par 11 , Cromossomos Humanos Par 1 , Leucemia Mielomonocítica Aguda/genética , Translocação Genética , Sequência de Bases , Pré-Escolar , Feminino , Humanos , Hibridização in Situ Fluorescente , Lactente , Cariotipagem , Masculino , Dados de Sequência MolecularRESUMO
A permanent cell line, LEF1, has been established from the cells of an adult suffering from a Philadelphia positive acute lymphoblastic leukemia. The LEF1 cell line was obtained by maintaining peripheral blood cells from the patient in culture on a fibroblast feeder; subsequently, an autonomously growing cell population, independent of that feeder layer, developed. The karyotype of the cell line, 46, t(9;22)(q34;q11), was different from the karyotype at diagnosis which had 53 chromosomes and two Philadelphia chromosomes. Furthermore, compared with the initial leukemic blasts, the immortalized cell had three differences in surface phenotype (CD23+, CD11b-, CD10-). However, molecular studies indicated that the breakpoint in the 3' part of the first intron of the BCR gene was unchanged, confirming the leukemic origin of LEF1. The cell line was shown to be Epstein-Barr virus negative.
Assuntos
Antígenos de Diferenciação de Linfócitos B/análise , Oncogenes , Cromossomo Filadélfia , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Receptores Fc/análise , Adulto , Antígenos CD/análise , Northern Blotting , Southern Blotting , Divisão Celular , Feminino , Citometria de Fluxo , Humanos , Fenótipo , Leucemia-Linfoma Linfoblástico de Células Precursoras/imunologia , Leucemia-Linfoma Linfoblástico de Células Precursoras/patologia , Receptores de IgE , Mapeamento por Restrição , Células Tumorais Cultivadas/imunologia , Células Tumorais Cultivadas/patologiaRESUMO
Molecular rearrangements of Ph1 chromosome, the hallmark of CML, are clustered in a 5.8-kb DNA segment, the so-called breakpoint cluster region (bcr) of the phl gene that is localized to chromosome 22q11. In Ph1-positive (Ph1+) ALLs, the rearrangements have been shown to involve either the 5.8-kb bcr (called bcr+) or a region upstream of bcr in the 5' end of the phl gene (bcr-). To gain insight into the rearrangements occurring in Ph1+ acute leukemias, a 64-kb DNA fragment from the 5' end of phl was analyzed in order to generate molecular probes covering 40 kb of the phl gene first intron. A panel of seven cases of bcr-Ph1+ acute leukemia (three nonlymphocytic and four lymphocytic) was investigated with these intron 1-derived probes. Strikingly, in six of the seven leukemias, the breakpoints were located in a 10.8-kb DNA segment, defining a new bcr which appears to be specific for Ph1+ acute leukemias. By analogy with the CML bcr region located in the 3' part of the phl gene, we propose to designate this 10.8-kb fragment bcr2.
Assuntos
Cromossomos Humanos Par 22 , Leucemia Mieloide Aguda/genética , Oncogenes , Cromossomo Filadélfia , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Mapeamento Cromossômico , Clonagem Molecular , Humanos , Recombinação Genética , Mapeamento por RestriçãoRESUMO
Rearrangements of the BCL2 gene and expression of bcl-2 protein were analyzed in a series of 64 cases of follicular lymphomas in order to establish a relationship between the rearrangements and the protein overexpression. Of the 64 cases, 41 showed BCL2 rearrangement involving one of the three breakpoint clusters: 30 in mbr, eight in mcr, and three in vcr. A double rearrangement mbr+vcr was detected in two cases. Twenty cases with bcl-2 protein expression in tumor cells exhibited no apparent rearrangement, suggesting the possible existence of other mechanisms activating the gene. Interestingly, expression of the LMP1 protein, the Epstein-Barr virus (EBV) encoded gene, whose capacity to induce BCL2 has been recently demonstrated, was only found in 2/41 cases in which BCL2 was rearranged. These data suggest that EBV infection is not an important mechanism in the activation of BCL2 in follicular lymphoma.
Assuntos
Regulação Neoplásica da Expressão Gênica/fisiologia , Linfoma Folicular/genética , Proteínas Proto-Oncogênicas/genética , Antígenos Virais/fisiologia , Rearranjo Gênico/fisiologia , Herpesvirus Humano 4/genética , Herpesvirus Humano 4/imunologia , Herpesvirus Humano 4/fisiologia , Humanos , Imuno-Histoquímica , Linfoma Folicular/química , Linfoma Folicular/imunologia , Proteínas Proto-Oncogênicas/análise , Proteínas Proto-Oncogênicas c-bcl-2 , Ativação Transcricional , Translocação Genética/genética , Regulação para Cima/fisiologia , Proteínas da Matriz Viral/fisiologiaRESUMO
A patient with acute monocytic leukemia (AMoL) and t(6;11)(q27;q23) developed acute lymphoblastic leukemia (ALL) and t(4;11)(q21;23), 10 months after complete remission of the AMoL. The MLL gene, normally located at band 11q23, appeared differently rearranged in the cells of these two leukemias, showing a different origin for the two malignant clones. The responsibility of etoposide, used in treatment of the AML, in the occurrence of the ALL is probable in this patient.