Stainless steel is a promising electrode material for anodes of microbial fuel cells.

The abilities of carbon cloth, graphite plate and stainless steel to form microbial anodes were compared under identical conditions. Each electrode was polarised at −0.2 V vs. SCE in soil leachate and fed by successive additions of 20 mM acetate. Under these conditions, the maximum current densities provided were on average 33.7 A m−2 for carbon cloth, 20.6 A m−2 for stainless steel, and 9.5 A m−2 for flat graphite. The high current density obtained with carbon cloth was obviously influenced by the three dimensional electrode structure. Nevertheless, a fair comparison between flat electrodes demonstrated the great interest of stainless steel. The comparison was even more in favour of stainless steel at higher potential values. At +0.1 V vs. SCE stainless steel provided up to 35 A m−2, while graphite did not exceed 11 A m−2. This was the first demonstration that stainless steel offers a very promising ability to form microbial anodes. The surface topography of the stainless steel did not significantly affect the current provided. Analysis of the voltammetry curves allowed two groups of electrode materials to be distinguished by their kinetics. The division into two well-defined kinetics groups proved to be appropriate for a wide range of microbial anodes described in the literature

Electroactivity of phototrophic river biofilms and constitutive cultivable bacteria

Electroactivity is a property of microorganisms assembled in biofilms that has been highlighted in a variety of environments. This characteristic was assessed for phototrophic river biofilms at the community scale and at the bacterial population scale. At the community scale, electroactivity was evaluated on stainless steel and copper alloy coupons used both as biofilm colonization supports and as working electrodes. At the population scale, the ability of environmental bacterial strains to catalyze oxygen reduction was assessed by cyclic voltammetry. Our data demonstrate that phototrophic river biofilm development on the electrodes, measured by dry mass and chlorophyll a content, resulted in significant increases of the recorded potentials, with potentials of up to +120 mV/saturated calomel electrode (SCE) on stainless steel electrodes and +60 mV/SCE on copper electrodes. Thirty-two bacterial strains isolated from natural phototrophic river biofilms were tested by cyclic voltammetry. Twenty-five were able to catalyze oxygen reduction, with shifts of potential ranging from 0.06 to 0.23 V, cathodic peak potentials ranging from −0.36 to −0.76 V/SCE, and peak amplitudes ranging from −9.5 to −19.4 μA. These isolates were diversified phylogenetically (Actinobacteria, Firmicutes, Bacteroidetes, and Alpha-, Beta-, and Gammaproteobacteria) and exhibited various phenotypic properties (Gram stain, oxidase, and catalase characteristics). These data suggest that phototrophic river biofilm communities and/or most of their constitutive bacterial populations present the ability to promote electronic exchange with a metallic electrode, supporting the following possibilities: (i) development of electrochemistry-based sensors allowing in situ phototrophic river biofilm detection and (ii) production of microbial fuel cell inocula under oligotrophic conditions

DGKI Methylation Status Modulates the Prognostic Value of MGMT in Glioblastoma Patients Treated with Combined Radio-Chemotherapy with Temozolomide

International audienceBackgroundConsistently reported prognostic factors for glioblastoma (GBM) are age, extent of surgery, performance status, IDH1 mutational status, and MGMT promoter methylation status. We aimed to integrate biological and clinical prognostic factors into a nomogram intended to predict the survival time of an individual GBM patient treated with a standard regimen. In a previous study we showed that the methylation status of the DGKI promoter identified patients with MGMT-methylated tumors that responded poorly to the standard regimen. We further evaluated the potential prognostic value of DGKI methylation status.Methods399 patients with newly diagnosed GBM and treated with a standard regimen were retrospectively included in this study. Survival modelling was performed on two patient populations: intention-to-treat population of all included patients (population 1) and MGMT-methylated patients (population 2). Cox proportional hazard models were fitted to identify the main prognostic factors. A nomogram was developed for population 1. The prognostic value of DGKI promoter methylation status was evaluated on population 1 and population 2.ResultsThe nomogram-based stratification of the cohort identified two risk groups (high/low) with significantly different median survival. We validated the prognostic value of DGKI methylation status for MGMT-methylated patients. We also demonstrated that the DGKI methylation status identified 22% of poorly responding patients in the low-risk group defined by the nomogram.ConclusionsOur results improve the conventional MGMT stratification of GBM patients receiving standard treatment. These results could help the interpretation of published or ongoing clinical trial outcomes and refine patient recruitment in the future

DNA methylation in glioblastoma: impact on gene expression and clinical outcome

International audienceBACKGROUND: Changes in promoter DNA methylation pattern of genes involved in key biological pathways have been reported in glioblastoma. Genome-wide assessments of DNA methylation levels are now required to decipher the epigenetic events involved in the aggressive phenotype of glioblastoma, and to guide new treatment strategies. RESULTS: We performed a whole-genome integrative analysis of methylation and gene expression profiles in 40 newly diagnosed glioblastoma patients. We also screened for associations between the level of methylation of CpG sites and overall survival in a cohort of 50 patients uniformly treated by surgery, radiotherapy and chemotherapy with concomitant and adjuvant temozolomide (STUPP protocol). The methylation analysis identified 616 CpG sites differentially methylated between glioblastoma and control brain, a quarter of which was differentially expressed in a concordant way. Thirteen of the genes with concordant CpG sites displayed an inverse correlation between promoter methylation and expression level in glioblastomas: B3GNT5, FABP7, ZNF217, BST2, OAS1, SLC13A5, GSTM5, ME1, UBXD3, TSPYL5, FAAH, C7orf13, and C3orf14. Survival analysis identified six CpG sites associated with overall survival. SOX10 promoter methylation status (two CpG sites) stratified patients similarly to MGMT status, but with a higher Area Under the Curve (0.78 vs. 0.71, p-value < 5e-04). The methylation status of the FNDC3B, TBX3, DGKI, and FSD1 promoters identified patients with MGMT-methylated tumors that did not respond to STUPP treatment (p-value < 1e-04). CONCLUSIONS: This study provides the first genome-wide integrative analysis of DNA methylation and gene expression profiles obtained from the same GBM cohort. We also present a methylome-based survival analysis for one of the largest uniformly treated GBM cohort ever studied, for more than 27,000 CpG sites. We have identified genes whose expression may be tightly regulated by epigenetic mechanisms and markers that may guide treatment decisions

Étude du méthylome des glioblastomes de l'adulte

Les glioblastomes sont les tumeurs primitives d'un système nerveux central les plus fréquentes et les plus agressives. Ce cancer est aujourd'hui incurable et le pronostic des patients, dramatique. Les glioblastomes sont caractérisés par une très forte hétérogénéité en terme d'altérations moléculaires, de pronostic, de réponse thérapeutique. Néanmoins, très peu de biomarqueurs ont été identifiés à ce jour. La méthylation de l'ADN joue un rôle majeur dans l'orchestration de l'expression génique. Les altérations de la méthylation de l'ADN sont fréquentes dans les cancers. Elles représentent des cibles thérapeutiques prometteuses et constituent d'excellents biomarqueurs utilisables en oncologie clinique. Dans ce contexte, les travaux de recherche menées au cours de cette thèse ont permis d'affiner la caractérisation moléculaire des glioblastomes en identifiant des gènes dont l'expression est à priori sous contrôle de la méthylation de leur promoteur, et d'identifier des biomarqueurs épigénétiques qui améliorent la stratification moléculaire des patients atteints d'un glioblastome. Ces résultats ouvrent de nombreuses perspectives à la fois en recherche translationnelle et fondamentale. Nos efforts sont désormais concentrés sur la validation des biomarqueurs épigénétiques identifiés en vue d'un transfert vers la clinique et sur leur étude fonctionnelle.Glioblastoma, the most common and most aggressive malignant primary brain tumour in adults, is characterised by a poor prognosis. This tumour is heterogeneous in terms of molecular alterations, prognosis, and therapeutic response. Despite this heterogeneity, few biomarkers have been associated with patient survival. DNA methylation plays a major role in orchestrating gene expression. Alterations in DNA methylation are common in cancers. They represent promising therapeutic targets and excellent biomarkers for use in clinical oncology. In this context, the research conducted during this thesis has led to refine the molecular characterization of glioblastoma by identifying genes whose expression is regulated by epigenetic mechanisms and identify epigenetic biomarkers that improve the molecular stratification of glioblastoma patients. These results open numerous perspectives in both fundamental and translational research. Our efforts are focused on the validation of the identified epigenetic biomarkers and on their functional study.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Intérêt de la MGMT dans les gliomes. [MGMT analysis in gliomas].

International audienceMGMT status is now regarded as a strong predictive factor of response to standard treatment of newly diagnosed glioblastomas involving temozolomide (TMZ) and radiotherapy. MGMT promoter methylation is also a prognostic factor - independent of treatment - in anaplastic gliomas. The predictive function can be explained by the role of the DNA repair enzyme MGMT, which antagonizes the effects of alkylating agents such as TMZ. MGMT promoter methylation could also reflect a particular molecular phenotype with its own specific prognostic significance. Since MGMT status determination is becoming a crucial biological marker in new clinical glioma trials, and is beginning to be used in day-to-day clinical practice, there is currently a strong need to determine the best technique for MGMT analysis. A French multicenter study has been set up for this purpose

From the core to beyond the margin: a genomic picture of glioblastoma intratumor heterogeneity

PMID 25940437International audienceGlioblastoma (GB) is a highly invasive primary brain tumor that almost systematically recurs despite aggressive therapies. One of the most challenging problems in therapy of GB is its extremely complex and heterogeneous molecular biology. To explore this heterogeneity, we performed a genome-wide integrative screening of three molecular levels: genome, transcriptome, and methylome. We analyzed tumor biopsies obtained by neuro-navigation in four distinct areas for 10 GB patients (necrotic zone, tumor zone, interface, and peripheral brain zone). We classified samples and deciphered a key genes signature of intratumor heterogeneity by Principal Component Analysis and Weighted Gene Co-expression Network Analysis. At the genome level, we identified common GB copy number alterations and but a strong interindividual molecular heterogeneity. Transcriptome analysis highlighted a pronounced intratumor architecture reflecting the surgical sampling plan of the study and identified gene modules associated with hallmarks of cancer. We provide a signature of key cancer-heterogeneity genes highly associated with the intratumor spatial gradient and show that it is enriched in genes with correlation between methylation and expression levels. Our study confirms that GBs are molecularly highly diverse and that a single tumor can harbor different transcriptional GB subtypes depending on its spatial architecture

Identification of two glioblastoma-associated stromal cell subtypes with different carcinogenic properties in histologically normal surgical margins.

International audienceGlioblastoma (GB) is a highly infiltrative tumor recurring within a few centimeters of the resection cavity in 90% of cases, even in cases of complete tumor resection and adjuvant chemo/radiotherapy. We recently isolated GB-associated stromal cells (GASCs) from the GB peritumoral zone, with phenotypic and functional properties similar to those of the cancer-associated fibroblasts (CAFs) present in the stroma of carcinomas. In particular, GASCs promote blood vessel development and have tumor-promoting effects on glioma cells in vitro and in vivo. In this study, we characterized these cells further, by analyzing the transcriptome and methylome of 14 GASC and five control stromal cell preparations derived from non-GB peripheral brain tissues. We identified two subtypes of GASCs in surgical margins in GB patients: GASC-A and GASC-B. GASC-B promoted the development of tumors and endothelium, whereas GASC-A did not. A difference in DNA methylation may underlie these two subtypes. We identified various proteins as being produced in the procarcinogenic GASC-B. Some of these proteins may serve as prognostic factors for GB and/or targets for anti-glioma treatment. In conclusion, in this era of personalized therapy, the status of GASCs in GB-free surgical margins should be taken into account, to improve treatment and the prevention of recurrence

Gene Expression Meta-Analysis Identifies Grading and Survival Markers in Anaplastic Glioma.

International audiencePurpose: Although molecular analyses have been shown to be useful for classifying tumors and formulating a prognosis for patients, current methods applied to glioma are mostly based on histopathology. To search for robust diagnostic and prognostic markers of high-grade gliomas (HGGs), we applied a meta-analysis that extracts the most reliable information from the available gene expression data. Methods: We obtained data sets from three studies in HGGs. We selected a consensus set of 267 patients. Differential analyses were performed separately for each study and we applied a meta-analysis approach based on nonparametric rank products to evaluate the combined data. The genes selected in both analyses were used to construct a gene classifier by logistic regression modeling. We performed survival analyses on 144 patients by fitting Cox proportional hazard model. Genes identified as both differentially expressed and correlated to survival were used to build an optimal survival model. Performances were evaluated on an independent data set comprising 54 patients. Several genes were validated using RT, Q-PCR, and immunohistochemistry on a local cohort of 130 patients. Results: This interstudy cross-validation approach generated a set of 65 genes consistently and specifically differentially expressed in GBM. Functional annotation revealed a clear association with the nervous system development and the cell communication. The genes significantly associated with grading were mostly related to the extracellular matrix. The optimal survival model was built on a four genes signature. Kaplan-Meier curves and the log rank test (training: p52 e-11, testing: p51 e-4) indicated the high survival prognostic potential for this classifier. Finally, applied only to GBM it clearly outperformed previous reports, by grouping GBM in two subtypes with significant different prognosis (p53 e-4). Conclusions: Meta-analysis allows the identification and validation of HGGs biomarkers that might represent good candidates for novel diagnostic and prognostic approaches in HGGs