Dorsal Anterior Cingulate Cortices Differentially Lateralize Prediction Errors and Outcome Valence in a Decision-Making Task.

The dorsal anterior cingulate cortex (dACC) is proposed to facilitate learning by signaling mismatches between the expected outcome of decisions and the actual outcomes in the form of prediction errors. The dACC is also proposed to discriminate outcome valence—whether a result has positive (either expected or desirable) or negative (either unexpected or undesirable) value. However, direct electrophysiological recordings from human dACC to validate these separate, but integrated, dimensions have not been previously performed. We hypothesized that local field potentials (LFPs) would reveal changes in the dACC related to prediction error and valence and used the unique opportunity offered by deep brain stimulation (DBS) surgery in the dACC of three human subjects to test this hypothesis. We used a cognitive task that involved the presentation of object pairs, a motor response, and audiovisual feedback to guide future object selection choices. The dACC displayed distinctly lateralized theta frequency (3–8 Hz) event-related potential responses—the left hemisphere dACC signaled outcome valence and prediction errors while the right hemisphere dACC was involved in prediction formation. Multivariate analyses provided evidence that the human dACC response to decision outcomes reflects two spatiotemporally distinct early and late systems that are consistent with both our lateralized electrophysiological results and the involvement of the theta frequency oscillatory activity in dACC cognitive processing. Further findings suggested that dACC does not respond to other phases of action-outcome-feedback tasks such as the motor response which supports the notion that dACC primarily signals information that is crucial for behavioral monitoring and not for motor control

Implication des mécanismes de réparation de l'ADN dans la résistance des glioblastomes à la chimiothérapie : De l'identification de gènes candidats in silico à leur validation préclinique

Gliomas are common malignant tumors of the central nervous system whom oligodendrogliomas and glioblastomas are the major subtypes. Among them, oligodendrogliomas are distinguished by their remarkable sensitivity to chemotherapy, responding dramatically to treatment, contrasting with resistance of glioblastomas. Anaplastic oligodendrogliomas have loss of chromosomal arms 1p and 19q. This genetic alteration is statistically significantly associated with both chemosensitivity and longer recurrence-free survival after chemotherapy. We hypothesized that there are some resistance genes on this area, responsible for chemo-resistance of glioblastomas. Among them we focused on DNA-repair genes because they correct chemotherapy-induced adducts on DNA. We screened these genes with an in vitro chemosensitivity test that we developped, and identified 4 of them as involved in resistance of glioma cells to cisplatin : ercc1, ercc2, mutyh and pnkp. These results were confirmed with the gold standard chemotherapy drug : temozolomide. Expression of these genes were measured in resistant and sensitive human tumors, and the first 3 genes are overexpressed in glioblastomas. Thus, these genes can be considered as innovant targets of a chemo-sensitizing treatment. We entered a pre-clinical trial, financed by LNCC, to test this treatment on mice. We developped sub-cutaneous and intra-cerebral human xenografts of glioma on mice and treated them with siRNA directed to target genes, and with temozolomide. This treatment increased the tumor chemo-sensitivity, reducing tumoral volume. Our preclinical results confirmed both our in vitro data and the potentiality to chemosensitize glioblastoma using siRNA.Les tumeurs primitives du système nerveux central les plus fréquentes sont les gliomes et se classent en deux grandes catégories : les astrocytomes et les oligodendrogliomes. La survie des patients porteurs d'oligodendrogliomes est de 70 % à 5 ans alors qu'elle ne dépasse pas une année en moyenne pour les glioblastomes. La divergence de pronostic observée entre ces deux types de gliomes résulte d'une différence de sensibilité aux traitements conventionnels. La chimiothérapie classique appliquée à ces tumeurs permet en effet d'obtenir une réponse pour 90 % des oligodendrogliomes contrastant avec moins de 10 % pour les glioblastomes. La chimio-sensibilité particulière des oligodendrogliomes peut être la conséquence des altérations géniques survenant lors du processus oncogène. Elle résulterait de l'absence d'expression de gènes de résistance des régions chromosomiques 1p et 19q, gènes ainsi distinctement exprimés entre les deux entités tumorales. Les gènes de réparation de l'ADN peuvent rendre compte de la résistance aux traitements, puisque responsables de la correction des adduits créés par la chimiothérapie. Nous avons recherché grâce à une évaluation fonctionnelle in vitro, quels gènes de réparation de la région 1p/19q sont impliqués dans la correction des adduits du CDDP. Quatre gènes ont ainsi été identifiés : ercc1, ercc2, mutyh et pnkp. Ces résultats ont été vérifiés avec du témozolomide, la drogue de référence dans le traitement des gliomes. L'expression des ces gènes a été mesurée dans des extraits de tumeurs de patients, résistantes (glioblastomes) et sensibles (oligodendrogliomes) à la chimiothérapie, et les 3 premiers sont effectivement surexprimés dans les glioblastomes. Ces gènes définissent ainsi les cibles d'un traitement chimio-sensibilisant. Nous avons entrepris l'étude préclinique de ce traitement basé sur l'utilisation concomitante de siRNA dirigés contre les gènes d'intérêt et de chimiothérapie. Des modèles de gliomes humains sous-cutanés et intra-cérébraux résistants à la chimiothérapie ont été utilisés chez les souris. Le traitement chimio-sensibilisant ciblant ercc1 a significativement augmenté l'effet du témozolomide sur les tumeurs, permettant ainsi de diminuer leur volume. Il pourrait faire prochainement l'objet d'essais cliniques. Nos travaux, menés de l'in silico au stade préclinique, d'une part démontrent la validité de notre hypothèse, c'est-à-dire l'implication des gènes de réparation du 1p/19q dans la chimio-résistance, et conduisent surtout à une opportunité thérapeutique nouvelle de chimio-sensibilisation

Novel fingerprinting method characterises the necessary and sufficient structural connectivity from deep brain stimulation electrodes for a successful outcome

Deep brain stimulation (DBS) is a remarkably effective clinical tool, used primarily for movement/ndisorders. DBS relies on precise targeting of specific brain regions to rebalance the oscillatory behaviour/nof whole-brain neural networks. Traditionally, DBS targeting has been based upon animal/nmodels (such asMPTPfor Parkinson’s disease) but has also been the result of serendipity during/nhuman lesional neurosurgery. There are, however, no good animal models of psychiatric disorders/nsuch as depression and schizophrenia, and progress in this area has been slow. In this paper, we use/nadvanced tractography combined with whole-brain anatomical parcellation to provide a rational/nfoundation for identifying the connectivity ‘fingerprint’ of existing, successful DBS targets. This/nknowledge can then be used pre-surgically and even potentially for the discovery of novel targets. First,/nusing data from our recent case series of cingulate DBS for patients with treatment-resistant chronic/npain, we demonstrate how to identify the structural ‘fingerprints’ of existing successful and unsuccessful/nDBS targets in terms of their connectivity to other brain regions, as defined by the whole-brain/nanatomical parcellation. Second, we use a number of different strategies to identify the successful fingerprints/nof structural connectivity across four patients with successful outcomes compared with/ntwo patients with unsuccessful outcomes. This fingerprinting method can potentially be used presurgically/nto account for a patient’s individual connectivity and identify the best DBS target. Ultimately,/nour novel fingerprinting method could be combined with advanced whole-brain computational/nmodelling of the spontaneous dynamics arising from the structural changes in disease, to/nprovide new insights and potentially new targets for hitherto impenetrable neuropsychiatric/ndisorders.We thank Ms Eloise Starkfor her valuable comments. MLK was supported by the ERC ConsolidatorGrant:/nCAREGIVING (n. 615539) and the TrygFonden Charitable Foundation. GD was supported by the ERC Advanced/nGrant: DYSTRUCTURE (n. 295129), by the Spanish Research Project SAF2010-16085 and the FP7-ICT BrainScales

Spatial and temporal distribution of information processing in the human dorsal anterior cingulate cortex

The dorsal anterior cingulate cortex (dACC) is a key node in the human salience network. It has been ascribed motor, pain-processing and affective functions. However, the dynamics of information flow in this complex region and how it responds to inputs remain unclear and are difficult to study using non-invasive electrophysiology. The area is targeted by neurosurgery to treat neuropathic pain. During deep brain stimulation surgery, we recorded local field potentials from this region in humans during a decision-making task requiring motor output. We investigated the spatial and temporal distribution of information flow within the dACC. We demonstrate the existence of a distributed network within the anterior cingulate cortex where discrete nodes demonstrate directed communication following inputs. We show that this network anticipates and responds to the valence of feedback to actions. We further show that these network dynamics adapt following learning. Our results provide evidence for the integration of learning and the response to feedback in a key cognitive region

Illustrative cases.

<p>All MRI examinations were performed using a 1.5 Tesla scanner (Philips Medical System). Standard MRI work-up systematically comprised at least one series of T2-weighted images (turbo spin echo, repetition time msec (RT)/echo time msec (ET=0.625/120; numbers of signals averaged ((NAS)=2; turbo factor=15) and T1-weigthed images (spin echo, RT/ET= 500/10; NAS=2) obtained prior to and after gadolinium injection. Representative contrast-enhanced images from low (a,b,c) and high (d,e,f) levels of sVE patients. (A,B,C) 36 years old man, oligodendroglioma grade III, in the left posterior temporal region (6 cm major axis): (A) Sagittal T1-weighted image after gadolinium injection shows diffuse and extensive contrast enhancement, (B) axial T2-weighted image shows heterogeneous aspect and few perilesional edema of the same lesion with (C) T2/fluid attenuated inversion recovery (FLAIR) shows infiltrative lesion with mass effect on ventricular junction. On all panels, the tumor area is indicated using a dotted white line. For this patient, sVE=296 ng/mL and overall survival was 12 months. (D,E,F) 60 years old women, glioblastoma in the left parietal region (3.5 cm major axis): (D) Sagittal T1-weighted image after gadolinium injection shows a ring of contrast enhancement around an area of hypointensity (necrosis). (E) axial T2-weighted image (T2) shows irregular contours and significative perilesional edema. (F) T2/fluid attenuated inversion recovery (FLAIR) shows few mass effect. For this patient, sVE=1.843 µg/mL and overall survival was 36 months.</p

Evidence for Post-Translational Processing of Vascular Endothelial (VE)-Cadherin in Brain Tumors: Towards a Candidate Biomarker

<div><p>Vessel abnormalities are among the most important features in malignant glioma. Vascular endothelial (VE)-cadherin is of major importance for vascular integrity. Upon cytokine challenge, VE-cadherin structural modifications have been described including tyrosine phosphorylation and cleavage. The goal of this study was to examine whether these events occurred in human glioma vessels. We demonstrated that VE-cadherin is highly expressed in human glioma tissue and tyrosine phosphorylated at site Y⁶⁸⁵, a site previously found phosphorylated upon VEGF challenge, via Src activation. <i>In vitro</i> experiments showed that VEGF-induced VE-cadherin phosphorylation, preceded the cleavage of its extracellular adhesive domain (sVE, 90 kDa). Interestingly, metalloproteases (MMPs) secreted by glioma cell lines were responsible for sVE release. Because VEGF and MMPs are important components of tumor microenvironment, we hypothesized that VE-cadherin proteolysis might occur in human brain tumors. Analysis of glioma patient sera prior treatment confirmed the presence of sVE in bloodstream. Furthermore, sVE levels studied in a cohort of 53 glioma patients were significantly predictive of the overall survival at three years (HR 0.13 [0.04; 0.40] p≤0.001), irrespective to histopathological grade of tumors. Altogether, these results suggest that VE-cadherin structural modifications should be examined as candidate biomarkers of tumor vessel abnormalities, with promising applications in oncology. </p> </div

VE-cadherin expression and phosphorylation in human glioma tissues.

<p>(A,B) Representative (n=10 samples) micrographs of primary human glioma stained for VE-cadherin (in red; nuclei are stained in blue). Images were processed using Adobe Photoshop Scale bar: 25 μm. A capillary network positive for VE-cadherin was detected in all the tumors. (C) A 125 kDa fragment of VE-cadherin was highly detectable in glioblastoma (GBM) extract and not in non-tumor brain tissue (N). (D) Protein lysates from N and GBM were analyzed by SDS-PAGE and western blotting with the antiphophotyrosine antibody (clone 4G10). Several proteins with apparent molecular masses (indicated by filled arrowheads) ranging from 220 to 25 kDa displayed clearly strong tyrosine phosphorylation in GBM but not in non-tumor tissue. (E) 500 μg of GBM tissue lysate protein were immunoprecipitated with an anti-human VE-Cadherin antibody directed to C-term of the protein and blotted with the indicated antibodies (Ptyr or VE-cad). Immunoprecipitation of VE-cadherin from glioma extracts allowed to detect a tyrosine phosphorylated form of VE-cadherin. Sample loading was controlled using actin detection. (F) Active Src (phosphoY418) was highly detectable in GBM but not in non-tumor (N) brain extract. (G) Orthovanadate treated-HUVECs lysates (control: CTL) and GBM extracts (50 µg) were analyzed by western blot using antiphosphosite antibodies directed against Y⁶⁵⁸ and Y⁷³¹, and the antibody directed against pY⁶⁸⁵ VE-cadherin raised in our laboratories. Only pY⁶⁸⁵ was detected in GBM as in HUVECs upon VEGF stimulation (50 ng/mL). (H) Same experiment as described in (E), and immunoblotting with anti-Csk antibody and anti-pY⁶⁸⁵ VE-cadherin antibody. The association of Csk with VE-cadherin in GBM confirmed the phosphorylation at the site Y⁶⁸⁵ also detected with the antiphosphosite antibody. Filled arrowhead indicates the position of the IgG heavy chains of the crosslinking antibody. In all blots the position of size markers (in kDa) is indicated on the left. These experiments were repeated at least three times in a similar configuration.</p

Scheme for hypothetical mechanism of a link between VE-cadherin phosphorylation and cleavage.

<p>In tumours, VEGF secreted by tumoral cells bind to VEGFR2 which leads to src activation. Activated src rapidly phosphorylates VE-cadherin on Y685. This covalent modification of the protein is followed by the cleavage of its extracellular domain upon MMP2,9. </p

Metalloproteinases are secreted by glioma cell line and induced VE-cadherin cleavage.

<p>(A) Conditioned media from Astrocytoma grade IV (LN229, LN) and Astrocytoma grade III (U87, U) cells lines were tested for protease activities using a zymography assay. Inhibition of protease activities by EDTA identified MMPs. (B) U87 (U) cell line media induced VE-cadherin cleavage from HUVECs (90 kDa fragment). Glioma cell line conditioned media was added to HUVEC confluent monolayer during two hours and HUVEC (H) conditioned media was analyzed for sVE content by western blot. The effect was impaired by broad spectrum MMPs inhibitor (GM6001, I). (C) Western blot analysis of glioma patient sera at dilution 1:50, 1:100, 1:500 revealed the presence of the 90 kDa fragment of VE-cadherin (sVE). (D) Deglycosylation Assay of sVE in serum shows, using two different antibodies to sVE that the soluble fragment is glycosylated. </p