MET is required for the recruitment of anti-tumoural neutrophils

Mutations or amplification of the MET proto-oncogene are involved in the pathogenesis of several tumours, which rely on the constitutive engagement of this pathway for their growth and survival. However, MET is expressed not only by cancer cells but also by tumour-associated stromal cells, although its precise role in this compartment is not well characterized. Here we show that MET is required for neutrophil chemoattraction and cytotoxicity in response to its ligand hepatocyte growth factor (HGF). Met deletion in mouse neutrophils enhances tumour growth and metastasis. This phenotype correlates with reduced neutrophil infiltration to both the primary tumour and metastatic sites. Similarly, Met is necessary for neutrophil transudation during colitis, skin rash or peritonitis. Mechanistically, Met is induced by tumour-derived tumour necrosis factor (TNF)-α or other inflammatory stimuli in both mouse and human neutrophils. This induction is instrumental for neutrophil transmigration across an activated endothelium and for inducible nitric oxide synthase production upon HGF stimulation. Consequently, HGF/MET-dependent nitric oxide release by neutrophils promotes cancer cell killing, which abates tumour growth and metastasis. After systemic administration of a MET kinase inhibitor, we prove that the therapeutic benefit of MET targeting in cancer cells is partly countered by the pro-tumoural effect arising from MET blockade in neutrophils. Our work identifies an unprecedented role of MET in neutrophils, suggests a potential ‘Achilles’ heel’ of MET-targeted therapies in cancer, and supports the rationale for evaluating anti-MET drugs in certain inflammatory diseases

Analysis of human MDM4 variants in papillary thyroid carcinomas reveals new potential markers of cancer properties

A wild-type (wt) p53 gene characterizes thyroid tumors, except for the rare anaplastic histotype. Because p53 inactivation is a prerequisite for tumor development, alterations of p53 regulators represent an alternative way to impair p53 function. Indeed, murine double minute 2 (MDM2), the main p53 negative regulator, is overexpressed in many tumor histotypes including those of the thyroid. A new p53 regulator, MDM4 (a.k.a. MDMX or HDMX) an analog of MDM2, represents a new oncogene although its impact on tumor properties remains largely unexplored. We estimated levels of MDM2, MDM4, and its variants, MDM4-S (originally HDMX-S) and MDM4-211 (originally HDMX211), in a group of 57 papillary thyroid carcinomas (PTC), characterized by wt tumor protein 53, in comparison to matched contra-lateral lobe normal tissue. Further, we evaluated the association between expression levels of these genes and the histopathological features of tumors. Quantitative real-time polymerase chain reaction revealed a highly significant downregulation of MDM4 mRNA in tumor tissue compared to control tissue (P < 0.0001), a finding confirmed by western blot on a subset of 20 tissue pairs. Moreover, the tumor-to-normal ratio of MDM4 levels for each individual was significantly lower in late tumor stages, suggesting a specific downregulation of MDM4 expression with tumor progression. In comparison, MDM2 messenger RNA (mRNA) and protein levels were frequently upregulated with no correlation with MDM4 levels. Lastly, we frequently detected overexpression of MDM4-S mRNA and presence of the aberrant form, MDM4-211 in this tumor group. These findings indicate that MDM4 alterations are a frequent event in PTC. It is worthy to note that the significant downregulation of full-length MDM4 in PTC reveals a novel status of this factor in human cancer that counsels careful evaluation of its role in human tumorigenesis and of its potential as therapeutic target

Integrones: los coleccionistas de genes Integrons: gene collectors

Los integrones son estructuras genéticas que han despertado gran interés, debido a que algunos de ellos vehiculizan genes de resistencia a los antimicrobianos. Están formados por un fragmento que codifica una integrasa (intI) y, a continuación, una secuencia attI a la que se unen los genes en casetes que codifican diferentes mecanismos de resistencia. Dentro de intI, en su extremo 3´, hay una secuencia promotora Pc a partir de la cual se transcriben los casetes de resistencia integrados, ya que estos genes carecen de promotor. Sin embargo, estos casetes presentan una secuencia específica denominada attC, la cual es reconocida por la integrasa que se une, por recombinación, a la secuencia attI del integrón en la orientación adecuada para su expresión. Los integrones se han clasificado según la secuencia de su integrasa, pero en la actualidad se prefiere clasificarlos según su localización. Se habla, en general, de "integrones móviles" para referirse a aquellos asociados a secuencias de inserción, transposones y/o plásmidos conjugativos, los que en su mayoría median mecanismos de resistencia, y de "superintegrones", de localización cromosómica y con grandes arreglos de genes en casetes. Los integrones móviles de clase 1 son los más abundantes en aislamientos clínicos y suelen estar asociados a transposones del subgrupo Tn21, seguidos por los de clase 2, derivados principalmente de Tn7. Estos elementos no son móviles por sí mismos, pero su asociación con elementos que sí lo son facilita su transferencia horizontal, lo que explica su amplia difusión entre las bacterias. Esta revisión intenta recopilar la información disponible acerca de los integrones móviles descritos en Argentina hasta la fecha.<br>Integrons gained great interest due to their participation in resistance gene recruitment and expression. Their basic structure includes a fragment that encodes an integrase (intI) followed by a recognition sequence (attI) into which they may incorporate gene cassettes (encoding resistance mechanisms). A promoter (Pc) embedded within the integrase gene controls the transcription of integrated resistance markers, as these genes do not have their own promoters. When in cassettes, resistance genes are flanked by specific sequences (attC), which are recognized by the integrase that, by site specific recombination, incorporates them after attI in proper orientation for their expression. In the past, integrons were classified according to their sequence homology; currently they are classified according to their location. In general, they are divided into "mobile" integrons (those associated with insertion sequences, transposons and/or plasmids, being most of them associated with resistance mechanisms), and chromosomally-located "super" integrons with large arrangements of cassette genes. "Mobile" class 1 integrons are the most abundant in clinical isolates and are generally associated with Tn21 subgroup transposons, followed by class 2, derived primarily from Tn7. These elements are not mobile themselves, but their association with mobile platforms that facilitate horizontal transfer, explains their wide distribution among bacteria. This review also attempts to describe the mobile integrons described so far in Argentina

Detección de Genes qnr en Aislamientos de Enterobacterias con Resistencia Simultánea a Fluorquinolonas y Oximinocefalosporinas

Se analizaron cepas de enterobacterias con resistencia simultánea a oximinocefalosporinas y fluorquinolonas aisladas entre febrero y agosto de 2007 de pacientes hospitalizados en el Sanatorio Médico de Diagnóstico y Tratamiento, Santa Fe Argentina. Mediante PCR multiplex, se detectó la presencia de genes qnr en 4 de las 30 cepas analizadas, representando el 13% de las cepas estudiadas. Se detectó la presencia del gen qnrB en dos cepas de Enterobacter cloacae y Klebsiella pneumoniae respectivamente. Ninguna de las cepas estudiadas mostró la presencia de genes qnrA ni qnrS.Detection of qnr genes in enterobacteriaceae isolates with simultaneous resistance to oximinocephalosporins and fluoroquinolones. Enterobacteriaceae strains with simultaneous resistance to oximinocephalosporins and fluoroquinolones isolated from hospitalized patients in Sanatorio Medico de Diagnóstico y Tratamiento, Santa Fe Argentina, between February and August 2007 were analyzed. qnr genes was detected by multiplex PCR, in 4 of 30 tested strains, representing 13% of them. qnrB gene was detected in two strains of Enterobacter cloacae and Klebsiella pneumoniae respectively. qnrA and qnrS genes were not detected in the studied strains.Fil: Escobar, A.. Sanatorio Medico de Diagnóstico y Tratamiento. Sección Bacteriología; ArgentinaFil: Porto, Ayelen Patricia. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Cátedra de Microbiología General; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Joris, R.. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Cátedra de Microbiología General; ArgentinaFil: Sansevich, M. E.. Sanatorio Medico de Diagnóstico y Tratamiento. Sección Bacteriología; ItaliaFil: Gutkind, Gabriel Osvaldo. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Di Conza, José Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Cátedra de Microbiología General; ArgentinaFil: Truppia, L. A.. Sanatorio Medico de Diagnóstico y Tratamiento. Sección Bacteriología; Argentin

Characterisation of KLUA-9, a beta-lactamase from extended-spectrum cephalosporin-susceptible Kluyvera ascorbata, and genetic organisation of bla(KLUA-9)

This study characterised the genetic environment of the chromosomally encoded blaKLUA-9 gene from a clinical Kluyvera ascorbata isolate and performed a kinetic characterisation of KLUA-9. Purified KLUA-9 showed the highest catalytic efficacies towards benzylpenicillin, ampicillin, piperacillin, first-generation cephalosporins, cefuroxime and cefoperazone; like other 'cefotaximases', it showed a much higher rate of hydrolysis of cefotaxime than ceftazidime, whilst dicloxacillin, cefoxitin and imipenem behaved as poor substrates. A 9 kb insert from K. ascorbata was cloned (Escherichia coli KK68C1) and sequenced. blaKLUA-9 and its 266 bp upstream flanking region (almost identical to the integron-associated bla(CTX-M-2)) are preceded by an aspat variant, a ypdABC-like operon and two open reading frames with unknown functions. Unlike IS CRI -associated bla(CTX-M-2) genes, we failed to detect the putative orf513 recombination sites. Instead, we were able to localise the 5 bp target sites for insertion of ISEcp1B, suggesting that this element could be responsible for future (or still undetected) mobilisation of blaKLUA-9 to more efficiently transferred elements. (c) 2006 Elsevier B.V and the International Society of Chemotherapy. All rights reserved

Detección de variabilidad genética en aislamientos de Cercospora kikuchii contaminantes de un mismo sembradío de soja Detection of genetic variability in Cercospora kikuchii isolates from a single soybean field

El conocimiento de la epidemiología y la estructura poblacional de Cercospora kikuchii está poco desarrollado y no se han comunicado estudios al respecto en la Argentina. El objetivo de este trabajo fue seleccionar oligonucleótidos que permitan detectar variabilidad genética en aislamientos de C. kikuchii obtenidos a partir de soja proveniente de un mismo sembradío, mediante la aplicación de RAPD. Se trabajó con 6 aislamientos de C. kikuchii, 5 de ellos se obtuvieron a partir de trozos de tejido enfermo y el restante provenía de una colección de cultivos. De los 7 oligonucleótidos empleados, 5 resultaron útiles para el estudio poblacional de los aislamientos de C. kikuchii.Current knowledge about epidemiology and population structure of Cercospora kikuchii is little developed and no studies regarding this subject have been reported in Argentina. The aim of this work was to select primers to study genetic variability in C. kikuchii isolated from the same soybean field using RAPD (Random Amplified Polymorphism DNA). RAPD was applied to the DNA of 5 C. kikuchii, isolated from diseased tissue of the soybean in the same field, another isolate, from a strain collection. Out of seven primers, five of them proved to be useful to study the population of C. kikuchii isolates