RESUMO
Lead levels were measured by inductively coupled plasma mass spectrometry (ICP-MS) in umbilical cord blood samples of 150 neonates in an urban inner-city hospital. The mean (SD) gestation and birth weight of our cohort were 38.8 (1.7) weeks and 3,217 (519) grams. There were 89% African-Americans, 53% males and 79% were born via vaginal delivery. Mean (SD) maternal age was 24.5 (5.8) years. History of drug abuse and smoking was reported in 8.7% and 10.7% respectively, with only 1 mother reporting a history of high lead level in childhood. Prenatal vitamin intake was reported in 99.3%. Cord blood lead level was available in 144 patients, with lead level of <1µg/dL seen in 141 (97.9%) and>1 in 3 (2.1%) patients. No patient had cord blood lead level of >2µg/dL. High lead levels during childhood in high-risk urban population, however, suggest the need for intensive efforts for prevention of environmental exposure to lead in early childhood.
Assuntos
Sangue Fetal/química , Hospitais Urbanos , Chumbo/sangue , Peso ao Nascer , População Negra , Feminino , Idade Gestacional , Humanos , Recém-Nascido , Intoxicação por Chumbo/sangue , Masculino , Exposição Materna/estatística & dados numéricos , Michigan/epidemiologia , Gravidez , População Urbana , Adulto JovemAssuntos
Síndrome de Down/complicações , Leucemia Megacarioblástica Aguda/etiologia , Neoplasia Residual/diagnóstico , Adolescente , Adulto , Criança , Pré-Escolar , Análise Citogenética , Síndrome de Down/genética , Síndrome de Down/mortalidade , Feminino , Humanos , Lactente , Recém-Nascido , Leucemia Megacarioblástica Aguda/mortalidade , Leucemia Megacarioblástica Aguda/patologia , Masculino , Neoplasia Residual/genética , Neoplasia Residual/mortalidade , Prognóstico , Estudos Prospectivos , Taxa de Sobrevida , Adulto JovemRESUMO
t(8;21)(q22;q22) results in the AML1-ETO (A1E) fusion gene and is a common cytogenetic abnormality in acute myeloid leukemia (AML). Although insertions at the breakpoint region of the A1E fusion transcripts have been reported, additional structural alterations are largely uncharacterized. By RT-PCR amplifications and DNA sequencing, numerous in-frame and out-of-frame AML1b-ETO and AML1c-ETO transcripts were identified in 13 pediatric t(8;21) AMLs, likely resulting from alternate splicing, internal deletions and/or breakpoint region insertions involving both the AML1 (RUNX1) and ETO regions. The in-frame A1E fusion transcript forms represented minor forms. These structure alterations were found in AML1c-ETO but not AML1b-ETO transcripts in two adult t(8;21) AMLs. Although no analogous alterations were detected in native AML1b transcripts, identical alterations in native ETO transcripts were identified. When transfected into HeLa cells, only AML1b, and not the in-frame A1E forms, transactivated the GM-CSF promoter. In co-transfection experiments, the effects of A1E proteins on GM-CSF transactivation by AML1b ranged from repressive to activating. Our results demonstrate a remarkable and unprecedented heterogeneity in A1E fusion transcripts in t(8;21) myeloblasts and suggest that synthesis of alternate A1E transcript and protein forms can significantly impact the regulation of AML1 responsive genes.
Assuntos
Cromossomos Humanos Par 21 , Cromossomos Humanos Par 8 , Subunidade alfa 2 de Fator de Ligação ao Core/genética , Leucemia Mieloide Aguda/genética , Proteínas de Fusão Oncogênica/genética , RNA Mensageiro/genética , Translocação Genética , Processamento Alternativo , Sequência de Bases , Primers do DNA , Fator Estimulador de Colônias de Granulócitos e Macrófagos/genética , Humanos , Regiões Promotoras Genéticas , Proteína 1 Parceira de Translocação de RUNX1 , Reação em Cadeia da Polimerase Via Transcriptase ReversaAssuntos
Cromossomos Humanos Par 6 , Cromossomos Humanos Par 9 , Leucemia Mieloide/genética , Leucemia Mieloide/terapia , Translocação Genética , Doença Aguda , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Ensaios Clínicos como Assunto , Feminino , Humanos , Leucemia Mieloide/classificação , Masculino , Pessoa de Meia-Idade , Estudos Multicêntricos como Assunto , Prognóstico , Estudos Prospectivos , Estudos RetrospectivosRESUMO
Secreted protein, acidic and rich in cysteine (SPARC), is a matricellular glycoprotein with growth-inhibitory and antiangiogenic functions. Although SPARC has been implicated as a tumor suppressor in humans, its function in normal or malignant hematopoiesis has not previously been studied. We found that the leukemic cells of AML patients with MLL gene rearrangements express low to undetectable amounts of SPARC whereas normal hematopoietic progenitors and most AML patients express this gene. SPARC RNA and protein levels were also low or undetectable in AML cell lines with MLL translocations. Consistent with its tumor suppressive effects in various solid tumor models, exogenous SPARC protein selectively reduced the growth of cell lines with MLL rearrangements by inhibiting cell cycle progression from G1 to S phase. The lack of SPARC expression in MLL-rearranged cell lines was associated with dense promoter methylation. However, we found no evidence of methylation-based silencing of SPARC in primary patient samples. Our results suggest that low or absent SPARC expression is a consistent feature of AML cells with MLL rearrangements and that SPARC may function as a tumor suppressor in this subset of patients. A potential role of exogenous SPARC in the therapy of MLL-rearranged AML warrants further investigation.
Assuntos
Rearranjo Gênico , Leucemia Mieloide/metabolismo , Proteína de Leucina Linfoide-Mieloide/genética , Osteonectina/metabolismo , Doença Aguda , Sequência de Bases , Western Blotting , Linhagem Celular Tumoral , Primers do DNA , Histona-Lisina N-Metiltransferase , Humanos , Leucemia Mieloide/patologia , Osteonectina/genética , RNA Mensageiro/genética , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
From 1981 to 2000, a total of 1823 children with acute myeloid leukemia (AML) enrolled on four consecutive Pediatric Oncology Group (POG) clinical trials. POG 8101 demonstrated that the induction rate associated with the 3+7+7 combination of daunorubicin, Ara-C, and 6-thioguanine (DAT) was greater than that associated with an induction regimen used to treat acute lymphoblastic leukemia (82 vs 61%; P=0.02). Designed as a pilot study to determine the feasibility of administration of noncross-resistant drug pairs and later modified to assess the effect of dose intensification of Ara-C during the second induction course, POG 8498 confirmed the high initial rate of response to DAT (84.2%) and showed that dose intensification of Ara-C during the second induction course resulted in a trend toward higher event-free survival (EFS) estimates than did standard-dose DAT (2+5) during the second induction course (5 year EFS estimates, 22 vs 27%; P=0.33). Age <2 years and leukocyte count <100 000/mm3 emerged as significantly good prognostic factors. The most significant observation made in the POG 8498 study was the markedly superior outcome of children with Down's syndrome who were treated on the high-dose Ara-C regimen. POG 8821 compared the efficacy of autologous bone marrow transplantation (BMT) with that of intensive consolidation chemotherapy. Intent-to-treat analysis revealed similar 5-year EFS estimates for the group that underwent autologous BMT (36+/-4.7%) and for the group that received only intensive chemotherapy (35+/-4.5%) (P=0.25). There was a high rate of treatment-related mortality in the autologous transplantation group. The study demonstrated superior results of allogeneic BMT for patients with histocompatible related donors (5-year EFS estimate 63+/-5.4%) and of children with Down's syndrome (5-year EFS estimate, 66+/-8.6%). The POG 9421 AML study evaluated high-dose Ara-C as part of the first induction course and the use of the multidrug resistance modulator cyclosporine. Preliminary results showed that patients receiving both high-dose Ara-C for remission induction and the MDR modulator for consolidation had a superior outcome (5-year EFS estimate, 42+/-8.2%) than did patients receiving other treatment; however, the difference was not statistically significant. These four studies demonstrate the importance of dose intensification of Ara-C in the treatment of childhood AML; cytogenetics as the single most prognostic factor and the unique curability of AML in children with Down's syndrome.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Protocolos Antineoplásicos/normas , Leucemia Mieloide/terapia , Doença Aguda , Adolescente , Transplante de Medula Óssea , Criança , Pré-Escolar , Citarabina/uso terapêutico , Relação Dose-Resposta a Droga , Síndrome de Down/complicações , Síndrome de Down/tratamento farmacológico , Seguimentos , Humanos , Lactente , Recém-Nascido , Leucemia Mieloide/complicações , Leucemia Mieloide/mortalidade , Prognóstico , Indução de Remissão/métodos , Análise de Sobrevida , Resultado do TratamentoAssuntos
Proteínas de Ligação a DNA/genética , Desoxicitidina Quinase/genética , Leucemia Mieloide/genética , Fatores de Transcrição/genética , Doença Aguda , Proteínas de Ligação a DNA/metabolismo , Regulação Enzimológica da Expressão Gênica , Regulação Leucêmica da Expressão Gênica , Humanos , Fatores de Transcrição/metabolismo , Fatores Estimuladores UpstreamAssuntos
Antineoplásicos/uso terapêutico , Arsenicais/uso terapêutico , Leucemia Promielocítica Aguda/tratamento farmacológico , Óxidos/uso terapêutico , Tretinoína/uso terapêutico , Trióxido de Arsênio , Criança , Humanos , Leucemia Promielocítica Aguda/complicações , Indução de Remissão , Taxa de Sobrevida , Resultado do TratamentoRESUMO
AIMS: Because of the observation of an abundance of leukaemia/lymphoma cell microparticles in the bone marrow aspiration sample of a patient with Burkitt's leukaemia at diagnosis, the occurrence of this phenomenon in leukaemia/lymphoma samples with available immune phenotyping data was investigated retrospectively. METHODS: Flow cytometric immune phenotyping and spontaneous apoptosis analysis of the bone marrow mononuclear cell preparation of the index case were performed. Microparticles isolated form the bone marrow sample were also studied for the presence of leukaemia/lymphoma cell microparticles. List mode analysis of 225 cases of acute leukaemia or lymphoma with previously performed immune phenotyping was also carried out. RESULTS: The presence of leukaemia/lymphoma cell microparticles could be detected by flow cytometry and they were found to be different from apoptotic bodies. Leukaemia/lymphoma cell microparticles were released in all cases of mature B cell neoplasms studied, although this phenomenon was rare in precursor B cell disorders and acute myeloid leukaemia. CONCLUSIONS: The generation of leukaemia/lymphoma cell microparticles in mature B cell neoplasms appears to be a common phenomenon. The pathogenesis and clinical implications must be investigated.
Assuntos
Leucemia de Células B/patologia , Células da Medula Óssea/imunologia , Células da Medula Óssea/ultraestrutura , Linfoma de Burkitt/imunologia , Linfoma de Burkitt/patologia , Linfoma de Burkitt/virologia , Criança , Citoplasma/ultraestrutura , Infecções por Vírus Epstein-Barr/complicações , Infecções por Vírus Epstein-Barr/patologia , Humanos , Imunofenotipagem , Leucemia de Células B/imunologia , Leucemia de Células B/virologia , Estudos RetrospectivosAssuntos
Cistationina beta-Sintase/genética , Síndrome de Down/complicações , Leucemia Mieloide/genética , Mutação/genética , Doença Aguda , Estudos de Casos e Controles , Primers do DNA/química , Síndrome de Down/genética , Genótipo , Humanos , Leucemia Mieloide/complicações , Reação em Cadeia da Polimerase , Polimorfismo GenéticoRESUMO
The purpose of this study was to assess the effect of the multidrug resistance modulator cyclosporine (CsA) on the pharmacokinetics of etoposide and mitoxantrone in children with de novo acute myeloid leukemia (AML). Serial blood samples for pharmacokinetic studies were obtained in 38 children over a 24-h period following cytotoxin treatment with or without CsA on days 1 and 4. Drug concentrations were quantitated using validated HPLC methods, and pharmacokinetic parameters were determined using compartmental modeling with an iterative two-stage approach, implemented on ADAPT II software. Etoposide displayed a greater degree of interindividual variability in clearance and systemic exposure than mitoxantrone. With CsA treatment, etoposide and mitoxantrone mean clearance declined by 71% and 42%, respectively. These effects on clearance, in combination with the empiric 40% dose reduction for either cytotoxin, resulted in a 47% and 12% increases in the mean AUC for etoposide and mitoxantrone, respectively. There were no differences in the rates of stomatitis or infection between the two groups. CsA treatment resulted in an increased incidence of hyperbilrubinemia, which rapidly reversed upon conclusion of drug therapy. The variability observed in clearance, combined with the empiric 40% dose reduction of the cytotoxins, resulted in statistically similar systemic exposure and similar toxicity.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/farmacocinética , Ciclosporina/farmacocinética , Etoposídeo/farmacocinética , Leucemia Mieloide/tratamento farmacológico , Mitoxantrona/farmacocinética , Doença Aguda , Adolescente , Protocolos de Quimioterapia Combinada Antineoplásica/administração & dosagem , Protocolos de Quimioterapia Combinada Antineoplásica/sangue , Área Sob a Curva , Criança , Pré-Escolar , Cromatografia Líquida de Alta Pressão , Ciclosporina/administração & dosagem , Ciclosporina/toxicidade , Interações Medicamentosas , Resistência a Múltiplos Medicamentos , Etoposídeo/administração & dosagem , Etoposídeo/sangue , Feminino , Humanos , Lactente , Leucemia Mieloide/complicações , Masculino , Taxa de Depuração Metabólica/efeitos dos fármacos , Mitoxantrona/administração & dosagem , Mitoxantrona/sangueAssuntos
Distinções e Prêmios , Hematologia/história , Pediatria/história , Criança , História do Século XX , Humanos , MichiganAssuntos
Antimetabólitos Antineoplásicos/farmacologia , Metotrexato/farmacologia , Oxirredutases atuantes sobre Doadores de Grupo CH-NH/genética , Polimorfismo Genético , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Adolescente , Antimetabólitos Antineoplásicos/uso terapêutico , Criança , Pré-Escolar , DNA de Neoplasias/metabolismo , Resistência a Medicamentos , Genótipo , Heterozigoto , Homozigoto , Humanos , Lactente , Metotrexato/uso terapêutico , Metilenotetra-Hidrofolato Redutase (NADPH2) , Reação em Cadeia da Polimerase , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamento farmacológico , Leucemia-Linfoma Linfoblástico de Células Precursoras/enzimologiaRESUMO
The presence of sequence variants in the human reduced folate carrier (hRFC) was assessed in leukemia blasts from children with acute lymphoblastic leukemia (ALL) and in normal peripheral blood specimens. A CATG frame shift insertion at position 191 was detected in 10-60% of hRFC transcripts from 10 of 16 ALL specimens, by RFLP analysis and direct sequencing of hRFC cDNAs. In genomic DNAs prepared from 105 leukemia (n = 54) and non-leukemia (n = 51) specimens, PCR amplifications and direct sequencing of exon 3 identified a high-frequency G to A single nucleotide polymorphism at position 80 that resulted in a change of arginine-27 to histidine-27. The allelic frequencies of G/A80 were nearly identical for the non-leukemia (42.2% CGC and 57.8% CAC) and leukemia (40.7% CGC and 59.3% CAC) genomic DNAs. In cDNAs prepared from 10 of these ALL patients, identical allelic frequencies (40 and 60%, respectively) were recorded. In up to 62 genomic DNAs, hRFC-coding exons 4-7 were PCR-amplified and sequenced. A high-abundance C/T696 polymorphism was detected with nearly identical frequencies for both alleles, and a heterozygous C/A1242 sequence variant was identified in two ALL specimens. Both C/T696 and C/A1242 were phenotypically silent. In transport assays with [(3)H]methotrexate and [(3)H]5-formyl tetrahydrofolate, nearly identical uptake rates were measured for the arginine-27- and histidine-27-hRFC proteins expressed in transport-impaired K562 cells. Although there were no significant differences between the kinetic parameters for methotrexate transport for the hRFC forms, minor (approximately 2-fold) differences were measured in the K(i)s for other substrates including Tomudex, 5,10-dideazatetrahydrofolate, GW1843U89, and 10-ethyl-10-deazaaminopterin and for 5-formyl tetrahydrofolate.
Assuntos
Proteínas de Transporte/genética , Proteínas de Membrana Transportadoras , Polimorfismo de Nucleotídeo Único , Leucemia-Linfoma Linfoblástico de Células Precursoras/patologia , Substituição de Aminoácidos , Linfócitos B/metabolismo , Sequência de Bases , Transporte Biológico/genética , Criança , Análise Mutacional de DNA , DNA Complementar/química , DNA Complementar/genética , DNA de Neoplasias/química , DNA de Neoplasias/genética , Frequência do Gene , Humanos , Células K562 , Metotrexato/farmacocinética , Mutagênese Insercional , Plasmídeos/genética , Mutação Puntual , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , RNA Neoplásico/genética , RNA Neoplásico/metabolismo , Proteína Carregadora de Folato Reduzido , Células-Tronco/metabolismo , TransfecçãoRESUMO
Infantile or congenital cases of thrombotic microangiopathy have been reported that were familial and characterized by ongoing microangiopathic hemolysis and thrombocytopenia in the absence of regular fresh-frozen plasma transfusions. The authors describe a child with congenital microangiopathic hemolytic anemia and thrombocytopenia (CMHAT) who has received regular fresh-frozen plasma transfusions since infancy and has never had thrombotic complications. von Willebrand factor (vWF)-cleaving protease activity was studied in the patient's pretransfusion and posttransfusion plasma samples as well as in her parents' plasma. The effects of the patient's and a control subject's plasma on human microvascular endothelial cells were also investigated. Unusually large vWF multimers were present in the patient's plasma both before transfusion (thrombocytopenic) and after transfusion. Unlike cases of chronic relapsing thrombotic thrombocytopenic purpura, vWF-cleaving protease activity was present and treatment of cultured human endothelial cells with the patient's plasma did not induce apoptosis. These findings suggest that the patient with CMHAT may represent a different group in the broad spectrum of thrombotic microangiopathies.
Assuntos
Anemia Hemolítica Congênita/sangue , Metaloendopeptidases/sangue , Trombocitopenia/sangue , Fator de von Willebrand/metabolismo , Proteínas ADAM , Proteína ADAMTS13 , Anemia Hemolítica Congênita/complicações , Anemia Hemolítica Congênita/enzimologia , Apoptose , Transfusão de Sangue , Pré-Escolar , Endotélio Vascular/patologia , Feminino , Humanos , Lactente , Trombocitopenia/complicações , Trombocitopenia/congênito , Trombocitopenia/enzimologiaRESUMO
The downstream effects of p15 and p16 gene deletions and loss of transcripts on dihydrofolate reductase (DHFR) were examined in 63 B-precursor (BP) acute lymphoblastic leukaemia (ALL) samples. p15 and/or p16 gene deletions were seen in 6% and 8%, respectively, of BP-ALL samples; however, losses of p15 and/or p16 transcripts were seen in 26 out of 63 (41%) samples. Loss of p15 transcripts (36.5%) exceeded that for p16 (17.5%). For the 26 BP-ALLs that lacked p15 and/or p16 transcripts, only six (23%) exhibited low levels of DHFR by flow cytometry assay with Pt430, a fluorescent anti-folate. Conversely, 18 out of 37 (49%) BP-ALL samples with intact p15 and/or p16 genes and transcripts showed low levels of DHFR (P = 0.04). In p15- and p16-null K562 cells transfected with a tetracycline-inducible p15 cDNA construct, induction of p15 transcripts and protein was accompanied by decreased growth rates, decreased S-phase fraction, decreased retinoblastoma protein phosphorylation, and markedly reduced levels of DHFR transcripts and protein. Collectively, our results suggest that losses of p15 and/or p16 gene expression result in elevated levels of DHFR in BP-ALL in children. However, additional downstream factors undoubtedly also contribute to elevated levels of this enzyme target.
Assuntos
Linfoma de Burkitt/genética , Proteínas de Ciclo Celular , Deleção de Genes , Genes p16 , Tetra-Hidrofolato Desidrogenase/genética , Fatores de Transcrição/genética , Proteínas Supressoras de Tumor , Adolescente , Southern Blotting , Linfoma de Burkitt/enzimologia , Estudos de Casos e Controles , Ciclo Celular , Criança , Pré-Escolar , Intervalos de Confiança , Inibidor de Quinase Dependente de Ciclina p15 , Relação Dose-Resposta a Droga , Doxiciclina/farmacologia , Feminino , Citometria de Fluxo , Expressão Gênica/efeitos dos fármacos , Humanos , Lactente , Células K562 , Modelos Logísticos , Masculino , Razão de Chances , RNA Mensageiro/análise , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
PURPOSE: To assess thiopurine S-methyltransferase (TPMT) phenotype and genotype in patients who were intolerant to treatment with mercaptopurine (MP) or azathioprine (AZA), and to evaluate their clinical management. PATIENTS AND METHODS: TPMT phenotype and thiopurine metabolism were assessed in all patients referred between 1994 and 1999 for evaluation of excessive toxicity while receiving MP or AZA. TPMT activity was measured by radiochemical analysis, TPMT genotype was determined by mutation-specific polymerase chain reaction restriction fragment length polymorphism analyses for the TPMT*2, *3A, *3B, and *3C alleles, and thiopurine metabolites were measured by high-performance liquid chromatography. RESULTS: Of 23 patients evaluated, six had TPMT deficiency (activity < 5 U/mL of packed RBCs [pRBCs]; homozygous mutant), nine had intermediate TPMT activity (5 to 13 U/mL of pRBCs; heterozygotes), and eight had high TPMT activity (> 13.5 U/mL of pRBCs; homozygous wildtype). The 65.2% frequency of TPMT-deficient and heterozygous individuals among these toxic patients is significantly greater than the expected 10% frequency in the general population (P <.001, chi(2)). TPMT phenotype and genotype were concordant in all TPMT-deficient and all homozygous-wildtype patients, whereas five patients with heterozygous phenotypes did not have a TPMT mutation detected. Before thiopurine dosage adjustments, TPMT-deficient patients experienced more frequent hospitalization, more platelet transfusions, and more missed doses of chemotherapy. Hematologic toxicity occurred in more than 90% of patients, whereas hepatotoxicity occurred in six patients (26%). Both patients who presented with only hepatic toxicity had a homozygous-wildtype TPMT phenotype. After adjustment of thiopurine dosages, the TPMT-deficient and heterozygous patients tolerated therapy without acute toxicity. CONCLUSION: There is a significant (> six-fold) overrepresentation of TPMT deficiency or heterozygosity among patients developing dose-limiting hematopoietic toxicity from therapy containing thiopurines. However, with appropriate dosage adjustments, TPMT-deficient and heterozygous patients can be treated with thiopurines, without acute dose-limiting toxicity.
Assuntos
Antimetabólitos Antineoplásicos/efeitos adversos , Azatioprina/efeitos adversos , Mercaptopurina/efeitos adversos , Metiltransferases/deficiência , Metiltransferases/genética , Polimorfismo de Fragmento de Restrição , Trombocitopenia/induzido quimicamente , Adolescente , Adulto , Criança , Pré-Escolar , Feminino , Genótipo , Hospitalização , Humanos , Lactente , Masculino , Metiltransferases/metabolismo , Neoplasias/tratamento farmacológico , Fenótipo , Transfusão de Plaquetas , Fatores de Risco , Trombocitopenia/genéticaRESUMO
Acute myeloid leukemia (AML) has one of the lowest survival rates of childhood cancers. The first significant improvement in AML therapy started with the introduction of the now standard regimen of 3 days of anthracyclines and 7 days of cytarabine (Ara-C), the so-called 3+7 combinations. Several different therapeutic approaches have been taken in attempts to improve the outcome, including intensification of therapy both for remission induction and in the postremission phase. Intensification of postremission therapy included multiple courses of high-dose chemotherapy and/or myeloablative therapy followed by stem- cell rescue from either allogeneic or autologous sources. Furthermore, risk-tailored therapy is now possible, by cytogenetic risk stratification, promptness of remission induction, and identification of distinct clinical subgroups such as children with Down syndrome. This approach is rapidly changing potential therapeutic strategies for children with AML. It is in this changing mileu that we address the proper role of stem-cell transplantation, a modality that is changing (like chemotherapy) with expanding stem-cell sources and approaches to decrease transplant-related toxicity.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Transplante de Medula Óssea , Transplante de Células-Tronco Hematopoéticas , Leucemia Mieloide/terapia , Doença Aguda , Transplante de Medula Óssea/efeitos adversos , Criança , Síndrome de Down/complicações , Sobrevivência de Enxerto , Humanos , Leucemia Mieloide/classificação , Leucemia Mieloide/patologia , Prognóstico , Ensaios Clínicos Controlados Aleatórios como Assunto , Medição de Risco , Análise de SobrevidaRESUMO
The significantly higher event-free survival rates of Down syndrome (DS) children with acute myeloid leukemia compared with non-DS children is linked to increased sensitivity of DS myeloblasts to 1-beta-D-arabinofuranosylcytosine (ara-C) and the enhanced metabolism of ara-C to ara-C triphosphate (J. W. Taub et al., Blood, 87: 3395-3403, 1996). The cystathionine-beta-synthase (CBS) gene (localized to chromosome 21q22.3) may have downstream effects on reduced folate and S-adenosylmethionine pathways; ara-C metabolism and folate pools are linked by the known synergistic effect of sequential methotrexate and ara-C therapy. We have shown that relative CBS transcripts were significantly higher in DS compared with non-DS myeloblasts, and CBS transcript levels correlated with in vitro ara-C sensitivity (J. W. Taub et al., Blood, 94: 1393-1400, 1999). A leukemia cell line model to study the relationship of the CBS gene and ara-C metabolism/sensitivity was developed by transfecting CBS-null CCRF-CEM cells with the CBS cDNA. CBS-transfected cells were a median 15-fold more sensitive in vitro to ara-C compared with wild-type cells and generated 8.5-fold higher [3H]ara-C triphosphate levels after in vitro incubation with [3H]ara-C. Severe combined immunodeficient mice implanted with CBS-transfected CEM cells demonstrated greater responsiveness to therapy, reflected in significantly prolonged survivals after ara-C administration compared with mice implanted with wild-type cells and treated with the same dosage schedule. The transfected cells also demonstrated increased in vitro and in vivo sensitivity to gemcitabine. Deoxycytidine kinase (dCK) activity was approximately 22-fold higher in transfected CEM cells compared with wild-type cells. However, levels of dCK transcripts on Northern blots and protein levels on Western blots were nearly identical between CBS-transfected and wild-type cells. Collectively, these results suggest a posttranscriptional regulation of dCK in CBS-overexpressing cells that contributes to increased ara-C phosphorylation and drug activity. Further elucidating the mechanisms of increased sensitivity of DS cells to ara-C related to the CBS gene may lead to the application of these novel approaches to acute myeloid leukemia therapy for non-DS patients.