RESUMEN
Burkitt lymphoma (BL) features translocations linking c-myc to the immunoglobulin heavy chain (IgH) locus. By inserting a c-myc gene under the control of the 3'IgH locus control region (LCR) into the mouse genome, we generated c-myc-3'LCR mice that develop clonal BL or diffuse anaplastic lymphoma. We show in the present study that while BL from c-myc-3'LCR mice would be classified as pre-germinal center (GC) cells due to the absence of both BCL-6 expression and somatic hypermutation (SHM) in V(H) sequences, they show a high level of SHM focused on the c-myc oncogene itself. This observation suggests that the c-myc-3'IgH LCR tandem association drives development of lymphoma from naïve B cells by specifically recruiting AID activity on c-myc in a process that early becomes independent from antigen selection and where the successive rounds of SHM rather rely on the selection of the most efficient mutations for oncogene deregulation. Similar to the translocated c-myc gene in human BL, mutations were found in first exon and 5' flanking sequences of transgenic c-myc and specially focused on negative regulatory elements, thus leading to high and constitutive oncogene expression. In conclusion while 3'IgH transcriptional enhancers in c-myc-3'LCR mice first simply act in cis to slightly stimulate c-myc transcription in untransformed B cells, the occurrence of lymphoma appears to result from an additional mechanism necessitating AID-driven mutations within the first exon and 5' flanking sequences which does not occur in parallel but rather circumvents antigen-driven selection.
Asunto(s)
Genes myc/genética , Linfoma/genética , Mutación/genética , Hipermutación Somática de Inmunoglobulina/genética , Región de Flanqueo 5'/genética , Animales , Linfoma de Burkitt/genética , Linfoma de Burkitt/inmunología , Linfoma de Burkitt/patología , Análisis Mutacional de ADN , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Exones/genética , Perfilación de la Expresión Génica , Regulación Neoplásica de la Expresión Génica , Cadenas Pesadas de Inmunoglobulina/genética , Región Variable de Inmunoglobulina/genética , Región de Control de Posición/genética , Linfoma/inmunología , Ratones , Ratones Transgénicos , Datos de Secuencia Molecular , Proteínas Proto-Oncogénicas c-bcl-6 , ARN Mensajero/genética , ARN Mensajero/metabolismoRESUMEN
Several reports have demonstrated an important role of leukotriene B(4) (LTB(4)) in the immune system. We investigated whether leukemic blasts from acute myeloid leukemic (AML) and acute lymphoid leukemic (ALL) patients produced LTB(4), 12- and 15-hydroxyeicosatetraenoic acids (12-HETE and 15-HETE) and whether these compounds affected blast proliferation and apoptosis. Leukemic blasts from AML M(0-2) and ALL patients expressed 5-LOX, 12-LOX and 15-LOX transcripts. Quantitative polymerase chain reaction indicated that 5-LOX transcripts were far more abundant than 12-LOX and 15-LOX ones. Leukemic blasts expressed 5-LOX activating protein (FLAP) transcripts and produced LTB(4) in response to calcium ionophore. In contrast no 15-HETE production was found. Calcium ionophore-stimulated leukemic blasts produced 12-HETE but also released thromboxane A(2) suggesting that contaminating platelets accounted for the release of these compounds. No significant effect of LTB(4), 12-HETE or 15-HETE could be documented on leukemic blast growth and on their apoptose rate. Results of the present study indicate that immature form of leukemic blasts produce LTB(4). However, the three major lipoxygenase metabolites of arachidonic acid; i.e., LTB(4), 12-HETE or 15-HETE, had no evident effect on their growth and apoptosis. We may speculate that LTB(4)-derived blast cells might initiate, augment or prolong tissue inflammation and damages by affecting the marrow and blood cytokine network.
Asunto(s)
Araquidonato 12-Lipooxigenasa/metabolismo , Araquidonato 15-Lipooxigenasa/metabolismo , Araquidonato 5-Lipooxigenasa/metabolismo , Crisis Blástica/enzimología , Leucemia Mieloide Aguda/enzimología , Leucemia-Linfoma Linfoblástico de Células Precursoras/enzimología , Ácido 12-Hidroxi-5,8,10,14-Eicosatetraenoico/metabolismo , Apoptosis/fisiología , Araquidonato 12-Lipooxigenasa/genética , Araquidonato 15-Lipooxigenasa/genética , Araquidonato 5-Lipooxigenasa/genética , Ácido Araquidónico/metabolismo , Crisis Blástica/clasificación , Crisis Blástica/patología , Calcio/metabolismo , Proliferación Celular , Humanos , Ácidos Hidroxieicosatetraenoicos/metabolismo , Ionóforos/farmacología , Leucemia Mieloide Aguda/clasificación , Leucemia Mieloide Aguda/patología , Leucotrieno B4/metabolismo , Reacción en Cadena de la Polimerasa , Leucemia-Linfoma Linfoblástico de Células Precursoras/clasificación , Leucemia-Linfoma Linfoblástico de Células Precursoras/patología , ARN Mensajero/genética , ARN Mensajero/metabolismo , Tromboxano A2/metabolismoAsunto(s)
Crisis Blástica/enzimología , Ciclooxigenasa 2/metabolismo , Leucemia Mieloide Aguda/enzimología , Leucemia-Linfoma Linfoblástico de Células Precursoras/enzimología , Crisis Blástica/patología , Ciclooxigenasa 2/genética , Citometría de Flujo , Humanos , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patología , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/patología , ARN Mensajero/genética , ARN Mensajero/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Receptor Toll-Like 4/genética , Receptor Toll-Like 4/metabolismoRESUMEN
BACKGROUND: Plasma concentrations of sFlt-1, the soluble form of the vascular endothelial growth factor receptor (VEGF), markedly increase during coronary artery bypass graft (CABG) surgery with extracorporeal circulation (ECC). We investigated if plasma sFlt-1 values might be related to the occurrence of surgical complications after CABG. METHODS: Plasma samples were collected from the radial artery catheter before vascular cannulation and after opening the chest, at the end of ECC just before clamp release, after cross release, after weaning from ECC, at the 6th and 24th post-operative hour. Thirty one patients were investigated. The presence of cardiovascular, haematological and respiratory dysfunctions was prospectively assessed. Plasma sFlt-1 levels were measured with commercially ELISA kits. RESULTS: Among the 31 investigated patients, 15 had uneventful surgery. Patients with and without complications had similar pre-operative plasma sFlt-1 levels. Lowered plasma sFlt-1 levels were observed at the end of ECC in patients with haematological (p = 0.001, ANOVA) or cardiovascular (p = 0.006) impairments, but not with respiratory ones (p = 0.053), as compared to patients with uneventful surgery. CONCLUSION: These results identify an association between specific post-CABG complication and the lower release of sFlt-1 during ECC. sFlt-1-induced VEGF neutralisation might, thus, be beneficial to reduce the development of post-operative adverse effects after CABG.
Asunto(s)
Puente de Arteria Coronaria/métodos , Enfermedad Coronaria/sangre , Complicaciones Posoperatorias/epidemiología , Receptor 1 de Factores de Crecimiento Endotelial Vascular/sangre , Enfermedad Coronaria/cirugía , Ensayo de Inmunoadsorción Enzimática , Humanos , Incidencia , Periodo Intraoperatorio , PronósticoRESUMEN
BACKGROUND: This study was conducted to follow plasma concentrations of sFlt-1 and sKDR, two soluble forms of the vascular endothelial growth factor (VEGF) receptor in patients undergoing coronary artery bypass graft (CABG) surgery with extracorporeal circulation (ECC). METHODS: Plasma samples were obtained before, during and after surgery in 15 patients scheduled to undergo CABG. Levels of sFlt-1 and KDR levels were investigated using specific ELISA. RESULTS: A 75-fold increase of sFlt-1 was found during cardiac surgery, sFlt-1 levels returning to pre-operative values at the 6th post-operative hour. In contrast sKDR levels did not change during surgery. The ECC-derived sFlt-1 was functional as judge by its inhibitory effect on the VEGF mitogenic response in human umbilical vein endothelial cells (HUVECs). Kinetic experiments revealed sFlt-1 release immediately after the beginning of ECC suggesting a proteolysis of its membrane form (mFlt-1) rather than an elevated transcription/translation process. Flow cytometry analysis highlighted no effect of ECC on the shedding of mFlt-1 on platelets and leukocytes suggesting vascular endothelial cell as a putative cell source for the ECC-derived sFlt-1. CONCLUSION: sFlt-1 is released during CABG with ECC. It might be suggested that sFlt-1 production, by neutralizing VEGF and/or by inactivating membrane-bound Flt-1 and KDR receptors, might play a role in the occurrence of post-CABG complication.