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2.
Blood Adv ; 3(23): 4002-4020, 2019 12 10.
Artigo em Inglês | MEDLINE | ID: mdl-31809537

RESUMO

To address the global burden of sickle cell disease and the need for novel therapies, the American Society of Hematology partnered with the US Food and Drug Administration to engage the work of 7 panels of clinicians, investigators, and patients to develop consensus recommendations for clinical trial end points. The panels conducted their work through literature reviews, assessment of available evidence, and expert judgment focusing on end points related to patient-reported outcome, pain (non-patient-reported outcomes), the brain, end-organ considerations, biomarkers, measurement of cure, and low-resource settings. This article presents the findings and recommendations of the end-organ considerations, measurement of cure, and low-resource settings panels as well as relevant findings and recommendations from the biomarkers panel.


Assuntos
Anemia Falciforme/fisiopatologia , Cardiopatias/etiologia , Pneumopatias/etiologia , Insuficiência Renal Crônica/etiologia , Cardiopatias/patologia , Humanos , Pneumopatias/patologia , Insuficiência Renal Crônica/patologia
3.
Blood Adv ; 3(23): 3982-4001, 2019 12 10.
Artigo em Inglês | MEDLINE | ID: mdl-31809538

RESUMO

To address the global burden of sickle cell disease (SCD) and the need for novel therapies, the American Society of Hematology partnered with the US Food and Drug Administration to engage the work of 7 panels of clinicians, investigators, and patients to develop consensus recommendations for clinical trial end points. The panels conducted their work through literature reviews, assessment of available evidence, and expert judgment focusing on end points related to: patient-reported outcomes (PROs), pain (non-PROs), the brain, end-organ considerations, biomarkers, measurement of cure, and low-resource settings. This article presents the findings and recommendations of the PROs, pain, and brain panels, as well as relevant findings and recommendations from the biomarkers panel. The panels identify end points, where there were supporting data, to use in clinical trials of SCD. In addition, the panels discuss where further research is needed to support the development and validation of additional clinical trial end points.


Assuntos
Anemia Falciforme/diagnóstico , Encéfalo/fisiopatologia , Dor/etiologia , Medidas de Resultados Relatados pelo Paciente , Ensaios Clínicos como Assunto , Humanos , Dor/patologia
4.
Oncologist ; 23(12): 1520-1524, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30120160

RESUMO

On November 6, 2017, the U.S. Food and Drug Administration (FDA) granted regular approval to vemurafenib for the treatment of adult patients with Erdheim-Chester disease (ECD) with BRAFV600 mutation. ECD is a type of histiocytosis, a rare disorder characterized by an abnormal accumulation and behavior of cells of the mononuclear phagocytic system, which includes antigen-processing cells, dendritic cells, monocytes, or macrophages. Recently published data confirm a frequency of 54% of BRAFV600E mutations in patients with ECD.Approval was based on a cohort of 22 patients who received 960 mg of vemurafenib twice daily within the VE Basket Trial (MO28072), a single-arm, multicenter, multiple cohort study. Patients in the ECD cohort had histologically confirmed ECD with BRAFV600 mutations that were refractory to standard therapy. The ECD cohort achieved an overall response rate of 54.5% (95% confidence interval: 32.2-75.6), with a complete response rate of 4.5%. With a median duration of follow-up of 26.6 months, the median duration of response has not been reached. The most frequently reported adverse reactions (>50%) in the ECD cohort were arthralgia, rash maculo-papular, alopecia, fatigue, electrocardiogram QT interval prolonged, and skin papilloma. The median treatment duration for ECD patients in this study was 14.2 months. This article describes the FDA review of the vemurafenib efficacy supplement for patients with ECD with BRAFV600 mutations. IMPLICATIONS FOR PRACTICE: Vemurafenib, an oral monotherapy targeting a mutation in BRAF, is the first U.S. Food and Drug Administration approval for the treatment of Erdheim-Chester disease (ECD). ECD is an extremely rare hematopoietic neoplasm that represents clonal proliferation of myeloid progenitor cells. ECD may involve bone and one or more organ systems, primarily affecting adults in their 5th and 7th decades of life, with a slight male predominance. This approval provides an effective and reasonably safe therapy for patients with a serious and life-threatening condition for which no approved therapy exists.


Assuntos
Antineoplásicos/uso terapêutico , Doença de Erdheim-Chester/tratamento farmacológico , Proteínas Proto-Oncogênicas B-raf/genética , Vemurafenib/uso terapêutico , Adulto , Idoso , Antineoplásicos/farmacologia , Doença de Erdheim-Chester/patologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Mutação , Estados Unidos , United States Food and Drug Administration , Vemurafenib/farmacologia
6.
Hemoglobin ; 40(5): 295-299, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27643740

RESUMO

Renal dysfunction in sickle cell disease is not only a chronic comorbidity but also a mortality risk factor. Though renal dysfunction starts early in life in sickle cell patients, the predictors that can identify sickle cell disease patients at risk of developing renal dysfunction is not known. We used the Truven Health MarketScan® Medicaid Databases from 2007 to 2012. Incidence of new acute renal failure (ARF) and chronic kidney disease (CKD) was calculated in this cohort. There were 9481 patients with a diagnosis of sickle cell disease accounting for 64,201 hospital admissions, during the study period. Both ARF and CKD were associated with higher risk of inpatient mortality, longer duration of the hospital stay and expensive hospitalizations. The yearly incidence of new ARF in sickle cell disease patients was 1.4% and annual CKD incidence was 1.3%. The annual rate of new ARF and CKD in the control group was 0.4 and 0.6%, respectively. The most important predictors of new CKD were proteinuria, ARF and hypertension. Chronic kidney disease, hypertension and sickle cell crisis were the most important predictors of new ARF. The annual rate of incidences of ARF and CKD were 2- to 3-fold higher in sickle cell disease compared to the non sickle cell disease group. Besides the common risk factors for renal disease in the general population, it is imperative to monitor the sickle cell disease patients with more severe disease to prevent them from developing renal dysfunction.


Assuntos
Anemia Falciforme/complicações , Insuficiência Renal/etiologia , Injúria Renal Aguda/epidemiologia , Injúria Renal Aguda/prevenção & controle , Estudos de Coortes , Hospitalização , Humanos , Hipertensão/complicações , Incidência , Tempo de Internação , Mortalidade , Prevalência , Proteinúria/complicações , Insuficiência Renal/epidemiologia , Insuficiência Renal Crônica/epidemiologia , Insuficiência Renal Crônica/prevenção & controle , Fatores de Risco
7.
Case Rep Hematol ; 2016: 7231503, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27559485

RESUMO

Pernicious anemia is a common cause of vitamin B12 deficiency. Here, we discuss a case of a young woman who presented with severe anemia along with a history of iron deficiency anemia. After a review of her clinical presentation and laboratory data, we identified an autoimmune hemolytic anemia and a concomitant pernicious anemia. The concurrence of both these hematological diagnoses in a patient is rare.

8.
Case Rep Oncol ; 9(1): 182-7, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27064217

RESUMO

Hepatoid adenocarcinoma (HAC) is a rare extrahepatic tumor distinguished by having both hepatoid and adenomatous features, which can make the diagnosis challenging. Although it mostly originates in the stomach, several other sites of origin have been reported. We report a case of HAC originating in the duodenum, a very unusual location. We also discuss an approach to the diagnosis of HAC using morphological and immunohistochemical features, and explore possible therapeutic options.

10.
Blood Adv ; 1(3): 170-183, 2016 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-28203649

RESUMO

The low incidence of HIV-1 infection in patients with sickle cell disease (SCD) and inhibition of HIV-1 replication in vitro under the conditions of low intracellular iron or heme treatment suggests a potential restriction of HIV-1 infection in SCD. We investigated HIV-1 ex vivo infection of SCD peripheral blood mononuclear cells (PBMCs) and found that HIV-1 replication was inhibited at the level of reverse transcription (RT) and transcription. We observed increased expression of heme and iron-regulated genes, previously shown to inhibit HIV-1, including ferroportin, IKBα, HO-1, p21, and SAM domain and HD domain-containing protein 1 (SAMHD1). HIV-1 inhibition was less pronounced in hepcidin-treated SCD PBMCs and more pronounced in the iron or iron chelators treated, suggesting a key role of iron metabolism. In SCD PBMCs, labile iron levels were reduced and protein levels of ferroportin, HIF-1α, IKBα, and HO-1 were increased. Hemin treatment induced ferroportin expression and inhibited HIV-1 in THP-1 cells, mimicking the HIV-1 inhibition in SCD PBMCs, especially as hepcidin similarly prevented HIV-1 inhibition. In THP-1 cells with knocked down ferroportin, IKBα, or HO-1 genes but not HIF-1α or p21, HIV-1 was not inhibited by hemin. Activity of SAMHD1-regulatory CDK2 was decreased, and SAMHD1 phosphorylation was reduced in SCD PBMCs and hemin-treated THP-1 cells, suggesting SAMHD1-mediated HIV-1 restriction in SCD. Our findings point to ferroportin as a trigger of HIV-1 restriction in SCD settings, linking reduced intracellular iron levels to the inhibition of CDK2 activity, reduction of SAMHD1 phosphorylation, increased IKBα expression, and inhibition of HIV-1 RT and transcription.

11.
Case Rep Hematol ; 2015: 784783, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26137331

RESUMO

Aromatase inhibitors (AIs) are most commonly used for breast cancer patients with hormone receptor positive disease. Although the side effect profile of aromatase inhibitors is well known, including common side effects like arthralgia, bone pain, arthritis, hot flashes, and more serious problems like osteoporosis, we present a case of an uncommon side effect of these medications. We report the case of a postmenopausal woman on adjuvant hormonal therapy with anastrozole after completing definitive therapy for stage IIIB estrogen receptor-positive breast cancer, who was referred to hematology service for evaluation of persistent erythrocytosis. Primary and known secondary causes of polycythemia were ruled out. On further evaluation, we found that her erythrocytosis began after initiation of anastrozole and resolved after it was discontinued. We discuss the pathophysiology of aromatase inhibitor-induced erythrocytosis and reference of similar cases reported in the literature.

12.
Curr Med Res Opin ; 31(3): 513-23, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25495135

RESUMO

BACKGROUND: Over the past few decades, lifespans of sickle cell disease (SCD) patients have increased; hence, they encounter multiple complications. Early detection, appropriate comprehensive care, and treatment may prevent or delay onset of complications. OBJECTIVE: We collected longitudinal data on sickle cell disease (SCD) complication rates and associated resource utilization relative to blood transfusion patterns and iron chelation therapy (ICT) use in patients aged ≥16 years to address a gap in the literature. RESEARCH DESIGN AND METHODS: Medical records of 254 SCD patients ≥16 years were retrospectively reviewed at three US tertiary care centers. MAIN OUTCOME MEASURES: We classified patients into cohorts based on cumulative units of blood transfused and ICT history: <15 units, no ICT (Cohort 1 [C1]), ≥15 units, no ICT (Cohort 2 [C2]), and ≥15 units with ICT (Cohort 3 [C3]). We report SCD complication rates per patient per year; cohort comparisons use rate ratios (RRs). RESULTS: Cohorts had 69 (C1), 91 (C2), and 94 (C3) patients. Pain led to most hospitalizations (76%) and emergency department (ED) (82%) visits. Among transfused patients (C2+C3), those receiving ICT were less likely to experience SCD complications than those who did not (RR [95% CI] C2 vs. C3: 1.33 [1.25-1.42]). Similar trends (RR [95% CI]) were observed in ED visits and hospitalizations associated with SCD complications (C2 vs. C3, ED: 1.94 [1.70-2.21]; hospitalizations: 1.61 [1.45-1.78]), but not in outpatient visits. CONCLUSIONS: Although the most commonly reported SCD complication among all patients was pain, patients who received ICT were less likely to experience pain and other complications than those who did not. These results highlight the need for increased patient and provider education on the importance of comprehensive disease management.


Assuntos
Anemia Falciforme , Terapia por Quelação , Ferro/uso terapêutico , Dor , Adulto , Anemia Falciforme/complicações , Anemia Falciforme/diagnóstico , Anemia Falciforme/epidemiologia , Anemia Falciforme/terapia , Transfusão de Sangue/métodos , Transfusão de Sangue/estatística & dados numéricos , Terapia por Quelação/métodos , Terapia por Quelação/estatística & dados numéricos , Gerenciamento Clínico , Diagnóstico Precoce , Intervenção Médica Precoce , Feminino , Hospitalização , Humanos , Masculino , Registros Médicos Orientados a Problemas , Dor/etiologia , Dor/prevenção & controle , Estudos Retrospectivos , Prevenção Secundária , Oligoelementos/uso terapêutico , Estados Unidos/epidemiologia
13.
Br J Haematol ; 167(5): 687-91, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25146244

RESUMO

Using health insurance claims databases we compared the frequency/incidence of acute myeloid leukaemia (AML) and inpatient mortality in sickle cell disease (SCD) subjects taking (n = 1051), or not taking (n = 9203) hydroxycarbamide (HC). Patients taking HC were older (median 19 vs. 17 years of age), had a higher proportion of males (53% vs. 38%), and their median hospitalizations per year was five times greater than in SCD patients not on HC (all P < 0·001). No new AML cases occurred in HC-treated paediatric SCD patients. For adults, the new AML incidence with HC exposure was 10·7/10 000 patient years, vs. 4·0/10 000 patient years in subjects not on HC (P = 0·2), a possible AML risk ratio of 3·18. Adjustment for a probable database bias for AML diagnosis/ascertainment lowered the risk ratio to 0·94 (95% confidence interval = 0·16-5·47). Despite their greater disease severity, the inpatient mortality in SCD adults prescribed HC (0·29%) was lower than that of patients not taking the drug (0·42%, P = 0·032). In this SCD population we find no increased risk for AML with HC treatment. If such a risk is eventually proven, it will probably be lower than that for drugs with known AML association. By contrast, HC treatment appears to confer a survival benefit.


Assuntos
Anemia Falciforme , Antidrepanocíticos , Bases de Dados Factuais , Hospitalização , Hidroxiureia , Leucemia Mieloide Aguda , Adolescente , Adulto , Fatores Etários , Anemia Falciforme/tratamento farmacológico , Anemia Falciforme/mortalidade , Antidrepanocíticos/administração & dosagem , Antidrepanocíticos/efeitos adversos , Criança , Intervalo Livre de Doença , Feminino , Humanos , Hidroxiureia/administração & dosagem , Hidroxiureia/efeitos adversos , Leucemia Mieloide Aguda/etiologia , Leucemia Mieloide Aguda/mortalidade , Masculino , Fatores de Risco , Fatores Sexuais , Taxa de Sobrevida
14.
Case Rep Gastrointest Med ; 2014: 724256, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24872902

RESUMO

Lymphomas arising in the liver are extremely rare. Here, we describe a case of Hepatitis C virus infection with primary hepatic lymphoma (PHL) presenting with hyperbilirubinemia. A 45-year-old African American male presented with abdominal pain, pruritus, and itching for two days. CT of abdomen and pelvis with contrast showed numerous masses in the liver. The liver biopsy was consistent with diffuse large B cell lymphoma (DLBCL). Conventional chemotherapy was avoided initially because of hyperbilirubinemia. Hence, radiation therapy was given initially to reduce his bilirubin levels and tumor size. The patient was able to complete six cycles of rituximab combined with cyclophosphamide, adriamycin, vincristine, and prednisone (R-CHOP) chemotherapy and achieved a complete response verified by positron emission tomography-computed tomography (PET-CT). PHL should be considered when there are numerous space occupying liver lesions seen on imaging. Hyperbilirubinemia may be a reason for delay in treatment for some of these patients. Hence, the role of radiation therapy prior to treatment with R-CHOP is an alternative to management for stage IV diffuse large B cell lymphoma.

15.
BMJ Case Rep ; 20132013 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-23645646

RESUMO

Infections are a significant cause of morbidity and mortality in patients with sickle cell disease. Loss of splenic function in these patients makes them highly susceptible to some bacterial infections. Non-tuberculous mycobacterial infections in patients with sickle cell disease are extremely rare and only two cases have been reported previously. We describe a case of sepsis caused by non-tuberculous mycobacterium, Mycobacterium terrae complex in a patient with febrile sickle cell disease. M terrae complex is a rare clinical pathogen and this is the first reported case of sepsis secondary to this organism in a patient with sickle cell disease. The patient responded to imipenem and amikacin therapy.


Assuntos
Anemia Falciforme/complicações , Infecções por Mycobacterium não Tuberculosas/microbiologia , Micobactérias não Tuberculosas , Sepse/microbiologia , Adulto , Antibacterianos/uso terapêutico , Feminino , Humanos , Infecções por Mycobacterium não Tuberculosas/tratamento farmacológico , Infecções por Mycobacterium não Tuberculosas/etiologia , Sepse/tratamento farmacológico , Sepse/etiologia
16.
Eur J Haematol ; 87(3): 191-207, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21615795

RESUMO

Acute chest syndrome (ACS) is a common complication and reason for hospital admission in patients with sickle cell disease (SCD). It is also the most common cause of death in this patient population. Most of the time, the trigger for ACS in an individual patient cannot be identified. However, although infection is the most common identifiable cause for ACS, other important triggers are vaso-occlusive crisis (VOC) and asthma. This comprehensive review will focus on the pathogenesis, clinical characteristics, complications and treatment available to manage ACS. But importantly, this review will highlight new possible etiologies, with the goal of improving oxygenation and, therefore, a reduction in sickling and lung damage in this patient population.


Assuntos
Síndrome Torácica Aguda/etiologia , Anemia Falciforme/complicações , Síndrome Torácica Aguda/prevenção & controle , Síndrome Torácica Aguda/terapia , Arteriopatias Oclusivas/complicações , Asma/complicações , Humanos , Oxigênio
17.
Blood ; 114(11): 2299-306, 2009 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-19597182

RESUMO

Therapeutic regulation of globin genes is a primary goal of translational research aimed toward hemoglobinopathies. Signal transduction was used to identify chromatin modifications and transcription factor expression patterns that are associated with globin gene regulation. Histone modification and transcriptome profiling were performed using adult primary CD34(+) cells cultured with cytokine combinations that produced low versus high levels of gamma-globin mRNA and fetal hemoglobin (HbF). Embryonic, fetal, and adult globin transcript and protein expression patterns were determined for comparison. Chromatin immunoprecipitation assays revealed RNA polymerase II occupancy and histone tail modifications consistent with transcriptional activation only in the high-HbF culture condition. Transcriptome profiling studies demonstrated reproducible changes in expression of nuclear transcription factors associated with high HbF. Among the 13 genes that demonstrated differential transcript levels, 8 demonstrated nuclear protein expression levels that were significantly changed by cytokine signal transduction. Five of the 8 genes are recognized regulators of erythropoiesis or globin genes (MAFF, ID2, HHEX, SOX6, and EGR1). Thus, cytokine-mediated signal transduction in adult erythroid cells causes significant changes in the pattern of globin gene and protein expression that are associated with distinct histone modifications as well as nuclear reprogramming of erythroid transcription factors.


Assuntos
Citocinas/metabolismo , Células Eritroides/metabolismo , Hemoglobina Fetal/biossíntese , Histonas/metabolismo , Processamento de Proteína Pós-Traducional , Fatores de Transcrição/metabolismo , Adulto , Antígenos CD34 , Células Cultivadas , Células Eritroides/citologia , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Hemoglobinopatias/metabolismo , Humanos , RNA Polimerase II/metabolismo , Transdução de Sinais , Transcrição Gênica
18.
Biochim Biophys Acta ; 1782(9): 504-10, 2008 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-18586086

RESUMO

In vivo, inhibition of fetal hemoglobin (HbF) expression in humans around the time of birth causes the clinical manifestation of sickle cell and beta-thalassemia syndromes. Inhibition of HbF among cultured cells was recently described by the adenosine derivative molecule named SQ22536. Here, a primary cell culture model was utilized to further explore the inhibition of HbF by adenosine derivative molecules. SQ22536 demonstrated down-regulation of growth and HbF expression among erythroblasts cultured from fetal and adult human blood. The effects upon HbF were noted in a majority of cells, and quantitative PCR analysis demonstrated a transcriptional mechanism. Screening assays demonstrated that two additional molecules named 5'-deoxy adenosine and 2',3'-dideoxy adenosine had effects on HbF comparable to SQ22536. Other adenosine derivative molecules, adenosine receptor binding ligands, and cAMP-signaling regulators failed to inhibit HbF in matched cultures. These results suggest that structurally related ribofuranose-substituted adenosine analogues act through an unknown mechanism to inhibit HbF expression in fetal and adult human erythroblasts.


Assuntos
Adenosina/farmacologia , Eritroblastos/citologia , Eritroblastos/efeitos dos fármacos , Hemoglobina Fetal/biossíntese , Adenina/análogos & derivados , Adenina/química , Adenina/farmacologia , Adenosina/química , Adulto , Ciclo Celular/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Colforsina/farmacologia , AMP Cíclico/metabolismo , Desoxiadenosinas/química , Desoxiadenosinas/farmacologia , Didesoxiadenosina/química , Didesoxiadenosina/farmacologia , Eritropoetina/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Inativação Gênica/efeitos dos fármacos , Globinas/genética , Globinas/metabolismo , Humanos , Cinética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transdução de Sinais/efeitos dos fármacos , Fator de Células-Tronco/farmacologia , Fator de Crescimento Transformador beta/farmacologia
19.
Nat Med ; 13(9): 1096-101, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17721544

RESUMO

In thalassemia, deficient globin-chain production during erythropoiesis results in anemia. Thalassemia may be further complicated by iron overload (frequently exacerbated by blood transfusion), which induces numerous endocrine diseases, hepatic cirrhosis, cardiac failure and even death. Accumulation of iron in the absence of blood transfusions may result from inappropriate suppression of the iron-regulating peptide hepcidin by an erythropoietic mechanism. To test this hypothesis, we examined erythroblast transcriptome profiles from 15 healthy, nonthalassemic donors. Growth differentiation factor 15 (GDF15), a member of the transforming growth factor-beta superfamily, showed increased expression and secretion during erythroblast maturation. Healthy volunteers had mean GDF15 serum concentrations of 450 +/- 50 pg/ml. In comparison, individuals with beta-thalassemia syndromes had elevated GDF15 serum levels (mean 66,000 +/- 9,600 pg/ml; range 4,800-248,000 pg/ml; P < 0.05) that were positively correlated with the levels of soluble transferrin receptor, erythropoietin and ferritin. Serum from thalassemia patients suppressed hepcidin mRNA expression in primary human hepatocytes, and depletion of GDF15 reversed hepcidin suppression. These results suggest that GDF15 overexpression arising from an expanded erythroid compartment contributes to iron overload in thalassemia syndromes by inhibiting hepcidin expression.


Assuntos
Peptídeos Catiônicos Antimicrobianos/genética , Citocinas/sangue , Regulação da Expressão Gênica , Talassemia/sangue , Talassemia/genética , Perfilação da Expressão Gênica , Fator 15 de Diferenciação de Crescimento , Hepcidinas , Humanos , Reação em Cadeia da Polimerase , RNA Mensageiro/genética , Valores de Referência , Transcrição Gênica
20.
Blood ; 108(6): 2081-6, 2006 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-16735596

RESUMO

Interruption of the normal fetal-to-adult transition of hemoglobin expression should largely ameliorate sickle cell and beta-thalassemia syndromes. Achievement of this clinical goal requires a robust understanding of gamma-globin gene and protein silencing during human development. For this purpose, age-related changes in globin phenotypes of circulating human erythroid cells were examined from 5 umbilical cords, 99 infants, and 5 adult donors. Unexpectedly, an average of 95% of the cord blood erythrocytes and reticulocytes expressed HbA and the adult beta-globin gene, as well as HbF and the gamma-globin genes. The distribution of hemoglobin and globin gene expression then changed abruptly due to the expansion of cells lacking HbF or gamma-globin mRNA (silenced cells). In adult reticulocytes, less than 5% expressed gamma-globin mRNA. These data are consistent with a "switching" model in humans that initially results largely from gamma- and beta-globin gene coexpression and competition during fetal development. In contrast, early postnatal life is marked by the rapid accumulation of cells that possess undetectable gamma-globin mRNA and HbF. The silencing phenomenon is mediated by a mechanism of cellular replacement. This novel silencing pattern may be important for the development of HbF-enhancing therapies.


Assuntos
Hemoglobina Fetal/genética , Inativação Gênica , Adulto , Anemia Falciforme/sangue , Anemia Falciforme/genética , Anemia Falciforme/terapia , Sangue Fetal/metabolismo , Hemoglobina Fetal/metabolismo , Globinas/genética , Hemoglobina A/genética , Hemoglobina A/metabolismo , Humanos , Lactente , Recém-Nascido , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Talassemia beta/sangue , Talassemia beta/genética , Talassemia beta/terapia
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