RESUMO
Acute myeloid leukemia (AML) is a complex hematological disorder characterized by blockage of differentiation and high proliferation rates of myeloid progenitors. Anthracycline and cytarabinebased therapy has remained the standard treatment for AML over the last four decades. Although this treatment strategy has increased survival rates, patients often develop resistance to these drugs. Despite efforts to understand the mechanisms underlying cytarabine resistance, there have been few advances in the field. The present study developed an in vitro AML cell line model resistant to cytarabine (HL60R), and identified chromosomal aberrations by karyotype evaluation and potential molecular mechanisms underlying chemoresistance. Cytarabine decreased cell viability, as determined by MTT assay, and induced cell death and cell cycle arrest in the parental HL60 cell line, as revealed by Annexin V/propidium iodide (PI) staining and PI DNA incorporation, respectively, whereas no change was observed in the HL60R cell line. In addition, the HL60R cell line exhibited a higher tumorigenic capacity in vivo compared with the parental cell line. Notably, no reduction in tumor volume was detected in mice treated with cytarabine and inoculated with HL60R cells. In addition, western blotting revealed that the protein expression levels of Bcl2, Xlinked inhibitor of apoptosis protein (XIAP) and cMyc were upregulated in HL60R cells compared with those in HL60 cells, along with predominant nuclear localization of the p50 and p65 subunits of NFκB in HL60R cells. Furthermore, the antitumor effect of LQB118 pterocarpanquinone was investigated; this compound induced apoptosis, a reduction in cell viability and a decrease in XIAP expression in cytarabineresistant cells. Taken together, these data indicated that acquired cytarabine resistance in AML was a multifactorial process, involving chromosomal aberrations, and differential expression of apoptosis and cell proliferation signaling pathways. Furthermore, LQB118 could be a potential alternative therapeutic approach to treat cytarabineresistant leukemia cells.
Assuntos
Aberrações Cromossômicas , Leucemia Mieloide Aguda/tratamento farmacológico , Naftoquinonas/farmacologia , Pterocarpanos/farmacologia , Animais , Apoptose/efeitos dos fármacos , Apoptose/genética , Citarabina/uso terapêutico , Resistencia a Medicamentos Antineoplásicos/genética , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Células HL-60 , Humanos , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patologia , Masculino , Camundongos , Naftoquinonas/uso terapêutico , Pterocarpanos/uso terapêutico , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/genética , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
The discovery of the Ten-Eleven Translocation (TET) protein family was initiated by the identification of the MLL partner TET1, and of mutations in the TET2 gene in hematological malignancies including myeloproliferative neoplasms (MPN). TET1, 2 and 3 proteins hydroxylate 5-methylcytosine (5-mC) into 5-hydroxymethylcytosine (5-hmC) and further oxidize 5-hmC into 5-formylcytosine (5-fC) and 5-carboxylcytosine (5-caC). Previous studies highlight the involvement of TET proteins in somatic cells reprogramming into induced pluripotent stem cells (iPSC), particularly Tet1 and 2 in mouse and TET1 in human. Here, we asked whether endogenous TET2 knockdown also displays this function. Using different shRNA against TET2, we provide evidence that TET2 strongly decreases the reprogramming of human hematopoietic progenitor cells into iPSC. Importantly, using 2 MPN patients, we observed that TET2 mutations affecting catalytic domain allowed iPSC generation. Instead, using another TET2 and TET3-mutated patient, we could only reprogram IPSC with TET3 mutation alone, suggesting that the type of TET2 mutation and/or the cooperation with TET3 mutations may alter the reprogramming activity. Altogether, this work highlights the importance of endogenous TET in the reprogramming process of human hematopoietic progenitors.
Assuntos
Proteínas de Ligação a DNA , Células-Tronco Pluripotentes Induzidas , Proteínas Proto-Oncogênicas , Animais , Metilação de DNA , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Dioxigenases , Haploinsuficiência , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Camundongos , Oxigenases de Função Mista/genética , Oxigenases de Função Mista/metabolismo , Mutação/genética , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismoAssuntos
Calreticulina/genética , Janus Quinase 2/genética , Mutação de Sentido Incorreto , Mielofibrose Primária , Trombocitemia Essencial , Adulto , Idoso , Idoso de 80 Anos ou mais , Substituição de Aminoácidos , Calreticulina/metabolismo , Feminino , Humanos , Janus Quinase 2/metabolismo , Masculino , Pessoa de Meia-Idade , Mielofibrose Primária/sangue , Mielofibrose Primária/genética , Mielofibrose Primária/patologia , Trombocitemia Essencial/sangue , Trombocitemia Essencial/genética , Trombocitemia Essencial/patologiaRESUMO
Polycythemia vera (PV), essential thrombocythemia (ET) and idiopathic myelofibrosis (IMF) are myeloproliferative disorders (MPD) that arise from the clonal proliferation of a pluripotent hematopoietic progenitor, leading to the overproduction of one or more myeloid lineages. Recently, a specific mutation in the JAK2 gene, which encodes a tyrosine kinase, has been shown to be associated with the myeloproliferative phenotype observed in PV, ET and IMF. In this study of Brazilian patients, the JAK2 V617F mutation [c.1887G > T) was detected in four out of 49 patients with PV (96 percent), 14 out of 25 patients with IMF (56 percent), and in eight out of 29 patients with ET, which is in accordance with previous screenings of this mutation in other populations.
