RESUMO
L-selectin is a cell adhesion molecule, expressed on leukocytes and involved in the regulation of leukocyte traffic. This adhesion receptor is implicated in hematopoiesis by the interaction of hematopoietic stem cells and progenitors to stroma in the bone marrow microenvironment. We found that L-selectin expression on CD34++ cells from patients with chronic myelogenous leukemia (CML) is decreased or deficient, reflecting one of the features of malignant CML progenitors. In this review, we briefly describe the structure and function of L-selectin, and its role in hematopoiesis and its expression in leukemia and lymphoma. Finally, we discuss the abnormal adhesiveness of CML progenitor cells, and the role of L-selectin in this defect.
Assuntos
Antígenos CD34 , Selectina L/biossíntese , Leucemia Mielogênica Crônica BCR-ABL Positiva/metabolismo , Células-Tronco Neoplásicas/metabolismo , Animais , Adesão Celular , Hematopoese , Humanos , Selectina L/fisiologia , Leucócitos/metabolismo , Células-Tronco Neoplásicas/citologiaRESUMO
Abnormal adhesive interaction between bone marrow stroma and progenitors, one of the causes of unregulated proliferation in chronic myelocytic leukaemia (CML), may be caused by some alterations in adhesion molecules on CML progenitors. We investigated the expression of adhesion molecules (CD44, VLA-5, VLA-4, LFA-1, ICAM-1, L-selectin and c-kit) on bone marrow CD34++ cells from 16 CML patients by three-colour flow cytometry. The mean percentage of cells expressing L-selectin in the CD34++CD38+(or)++ fraction from untreated CML patients was significantly lower, and that in the CD34++CD38- fraction tended to be lower than that from normal controls. Among 11 CML patients treated with interferon-alpha (IFN-alpha), the mean percentage of the cells expressing L-selectin in the CD34++CD38- fraction from three patients with a low percentage of Ph1(+) cells in bone marrow was significantly higher than that from five patients with a high percentage of Ph1(+) cells. In addition, L-selectin expression rate was inversely correlated to the percentage of Ph1(+) cells. There was no significant difference between the untreated patients and normal controls with regard to the expression rates of the other adhesion molecules in each CD34++ fraction except LFA-1. These data suggest that decreased L-selectin expression in CML CD34++ cells reflects one of the features of malignant CML progenitors.
Assuntos
Antígenos CD34/análise , Antígenos CD , Células-Tronco Hematopoéticas/metabolismo , Selectina L/metabolismo , Leucemia Mielogênica Crônica BCR-ABL Positiva/metabolismo , ADP-Ribosil Ciclase , ADP-Ribosil Ciclase 1 , Adulto , Idoso , Antígenos de Diferenciação/metabolismo , Cor , Citometria de Fluxo , Humanos , Molécula 1 de Adesão Intercelular/metabolismo , Interferon-alfa/uso terapêutico , Leucemia Mielogênica Crônica BCR-ABL Positiva/terapia , Glicoproteínas de Membrana , Pessoa de Meia-Idade , N-Glicosil Hidrolases/metabolismo , Proteínas Proto-Oncogênicas c-kit/metabolismo , Receptores de Antígeno muito Tardio/metabolismoRESUMO
Vascular endothelial growth factor (VEGF) has been identified as a peptide growth factor specific for vascular endothelial cells. In this study, we demonstrated the expression of the KDR gene transcript, which encodes a cell surface receptor for VEGF, in normal human hematopoietic stem cells, megakaryocytes, and platelets as well as in human leukemia cell lines, HEL and CMK86. Moreover, we showed the expression of VEGF gene transcript in these normal fresh cells and cell lines. To elucidate biological functions of VEGF on hematopoiesis, we determined whether this growth factor has mitogenic activity to hematopoietic cells or the ability to suppress apoptotic cell death. The liquid culture and colony-formation assay revealed that VEGF suppressed apoptotic cell death of both CMK86 cells and normal hematopoietic stem cells caused by gamma-ray irradiation, although mitogenic activity of VEGF was not detected. The ability of VEGF to suppress apoptotic cell death was independent of the change of cell cycle distribution. These data suggest that VEGF may play an important role in survival or maintenance of hematopoietic stem cells due to the prevention of apoptotic cell death caused by some stresses such as ionizing radiation and that VEGF may give leukemia cells some abilities of resistance against radiotherapy in an autocrine or paracrine manner.
Assuntos
Apoptose/efeitos dos fármacos , Fatores de Crescimento Endotelial/farmacologia , Células-Tronco Hematopoéticas/efeitos dos fármacos , Linfocinas/farmacologia , Receptores Proteína Tirosina Quinases/genética , Receptores de Fatores de Crescimento/genética , Sequência de Bases , Ciclo Celular/efeitos dos fármacos , Linhagem Celular , Fatores de Crescimento Endotelial/análise , Sangue Fetal/citologia , Células-Tronco Hematopoéticas/química , Células-Tronco Hematopoéticas/efeitos da radiação , Humanos , Linfocinas/análise , Dados de Sequência Molecular , Radiação Ionizante , Receptores de Fatores de Crescimento do Endotélio Vascular , Fator A de Crescimento do Endotélio Vascular , Fatores de Crescimento do Endotélio VascularRESUMO
We examined the expression of c-Mpl (MPL) and c-Mpl ligand (ML) gene in hematopoietic cells in individuals with and without myeloproliferative disorders (MPD) and leukemic cell lines by RT-PCR. The MPL gene transcripts were detected in normal CD34+ cells, platelets, megakaryocytes and monocytes, while the ML gene was expressed in CD34+ cells, megakaryocytes, T cells, monocytes and bone marrow fibroblasts, as well as liver tissue. The ML gene product produced in the bone marrow microenvironment might, in part, be involved in hematopoiesis. The MPL gene expression was detected in platelets and peripheral blood mononuclear cells from the majority of patients with MPD including chronic myelocytic leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF). In contrast, the ML gene expression was found in the majority of ET and CML patients, but not in PV or PMF patients. These findings suggest that even in MPD the megakaryocytopoiesis depends on the MPL signal transduction system, and that in ET and CML, the ML production by mononuclear cells in the bone marrow microenvironment might play a part in the higher megakaryocytopoiesis observed in these diseases. Both the MPL and ML gene expression were detected in all the leukemic cell lines tested, suggesting that this cytokine/receptor system is involved in cell growth through autocrine and paracrine systems.
Assuntos
Regulação Neoplásica da Expressão Gênica/fisiologia , Regulação da Expressão Gênica/fisiologia , Células-Tronco Hematopoéticas/metabolismo , Leucemia/genética , Transtornos Mieloproliferativos/genética , Proto-Oncogenes , Sequência de Bases , Humanos , Ligantes , Dados de Sequência Molecular , Células Tumorais CultivadasRESUMO
c-kit is a tyrosine kinase receptor whose ligand is stem cell factor (SCF). Gene alteration of the c-kit extracellular domain was analysed by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) in 25 patients with myeloproliferative disorders (MPD). In the N-terminal part of the domain, mobility shifts indicating sequence alteration were detected in three of the patients, two primary myelofibrosis (PMF) and one chronic myelogenous leukaemia (CML). The subsequent sequencing revealed the same point mutations at codon 52 causing amino acid substitution (Asp-->Asn). To our knowledge this is the first report with a c-kit point mutation found in human fresh tumour cells.
Assuntos
Transtornos Mieloproliferativos/genética , Mutação Puntual , Proteínas Proto-Oncogênicas c-kit/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Sequência de Bases , Feminino , Humanos , Leucemia Mielogênica Crônica BCR-ABL Positiva/genética , Masculino , Pessoa de Meia-Idade , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Polimorfismo Genético , Mielofibrose Primária/genética , Análise de SequênciaRESUMO
Blast cells from six patients with leukemic transformation of primary myelofibrosis (PMF) were studied by morphology, immunophenotype and genotype as well as response to hematopoietic growth factors. The majority of the patients showed granulocytic or granulo-monocytic blasts, and only one had T lymphoid-monocytic blasts. None of the patients showed rearrangement of Ig or TCR genes, or the existence of the bcr-abl fused gene. A prominent growth response to GM-CSF and IL-3 was evident in all of the patients examined in liquid as well as semisolid cultures. The response to G-CSF was observed in four of the six patients in suspension culture, and in two of three patients in the clonogenic assay. Stem cell factor (SCF) was a weak growth stimulant, however the combination of this factor with GM-CSF or IL-3 was synergistically stimulatory. These results suggest that leukemic transformation of PMF occurs mainly at the level of myeloid stem cell, and that GM-CSF, IL-3, G-CSF and SCF are major growth factors for the blast cells in these cases.