Assuntos
Países em Desenvolvimento , Educação Médica , Cooperação Internacional , Liderança , HumanosRESUMO
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an interferon (IFN)-induced molecule with apoptotic activity. We examined gene mutations in the death domains of TRAIL receptor 1 (TRAIL-R1) and TRAIL receptor 2 (TRAIL-R2), and in the TRAIL gene promoter in 46 chronic myelogenous leukemia (CML) patients. In 23 of the 46 patients, all the coding regions of TRAIL-R2 were also examined. However, no mutation or loss of heterozygosity was found. Furthermore, no mutation in the death domains of TRAIL-R1 and TRAIL-R2 genes, which causes amino acid change, was found in 18 myelodysplastic syndrome (MDS) patients. Ribonuclease protection assay (RPA) and real-time quantitative polymerase chain reaction using polymorphonuclear neutrophils of five new CML patients showed that the TRAIL mRNA expression was very low before in vitro IFN-alpha stimulation and markedly upregulated after IFN-alpha stimulation. FAS mRNA was also upregulated with IFN-alpha stimulation but the fold induction was far lower than that of TRAIL mRNA. In addition, RPA revealed that the ratio of (TRAIL-R1 plus TRAIL-R2) to TRAIL-R3 was also increased after IFN-alpha stimulation. Taken together, gene mutations of TRAIL-R1, TRAIL-R2 are infrequent in patients with CML and MDS. And so is the TRAIL promoter for CML. These mutations seem unrelated to tumorigenesis, disease progression, and response to IFN-alpha therapy in CML. A markedly high induction of TRAIL mRNA by IFN-alpha may have some relevance to IFN-alpha action in CML patients.
Assuntos
Substituição de Aminoácidos/genética , Regulação Leucêmica da Expressão Gênica/genética , Leucemia Mielogênica Crônica BCR-ABL Positiva/genética , Perda de Heterozigosidade/genética , Síndromes Mielodisplásicas/genética , Receptores do Fator de Necrose Tumoral/genética , Proteínas Reguladoras de Apoptose , Feminino , Regulação Leucêmica da Expressão Gênica/efeitos dos fármacos , Humanos , Fatores Imunológicos/farmacologia , Fatores Imunológicos/uso terapêutico , Interferon-alfa/farmacologia , Interferon-alfa/uso terapêutico , Leucemia Mielogênica Crônica BCR-ABL Positiva/tratamento farmacológico , Masculino , Glicoproteínas de Membrana/genética , Pessoa de Meia-Idade , Síndromes Mielodisplásicas/tratamento farmacológico , Fases de Leitura Aberta/genética , Regiões Promotoras Genéticas/genética , Estrutura Terciária de Proteína/genética , RNA Mensageiro/genética , Receptores do Ligante Indutor de Apoptose Relacionado a TNF , Ligante Indutor de Apoptose Relacionado a TNF , Células Tumorais Cultivadas , Fator de Necrose Tumoral alfa/genéticaRESUMO
In order to investigate the mechanism of interferon-alpha (IFNalpha) action in the treatment of chronic myelogenous leukemia (CML), we examined surface expressions of both type I interferon receptor 1 (IFNAR1) and 2 (IFNAR2) subunits on CD34-positive cells in bone marrow (BM) in a total of 57 CML patients. Initial cell-surface IFNAR2 expression at diagnosis assessed by flow cytometry widely distributed but showed overall significantly higher expression in CML patients when compared with normal controls. In 15 fresh patients who subsequently received IFNalpha therapy, IFNAR2 expression at diagnosis was significantly higher in cytogenetic good responders than in poor responders. Down-regulation of IFNAR2 expression during IFNalpha therapy was observed only in good responders but not in poor responders. In addition to protein level, both initial high IFNAR2c mRNA expression level and its down-regulation during IFNalpha therapy, in purified CD34-positive cells, were also observed only in good responders. In contrast to IFNAR2, cell-surface IFNAR1 expression was generally lower than IFNAR2, and correlation between either the pretreatment level or down-regulation of IFNAR1 and clinical response was not evident. With in vitro IFNalpha stimulation, CD34-positive cells showed down-regulations of cell-surface IFNAR2, and IFNAR1 to a lesser extent, in one good-responder patient, but not in one poor-responder patient. Serum soluble interferon receptor (sIFNR) was higher in untreated CML patients than in normal controls, without any correlation with clinical response to IFNalpha. Thus, the pretreatment protein and mRNA expression levels of IFNAR2 and their down-regulations during IFNalpha therapy correlate well with IFNalpha response in CML patients.
