A next step in adeno-associated virus-mediated gene therapy for neurological diseases: regulation and targeting.

Recombinant adeno-associated virus (rAAV) vectors mediating long term transgene expression are excellent gene therapy tools for chronic neurological diseases. While rAAV2 was the first serotype tested in the clinics, more efficient vectors derived from the rh10 serotype are currently being evaluated and other serotypes are likely to be tested in the near future. In addition, aside from the currently used stereotaxy-guided intraparenchymal delivery, new techniques for global brain transduction (by intravenous or intra-cerebrospinal injections) are very promising. Various strategies for therapeutic gene delivery to the central nervous system have been explored in human clinical trials in the past decade. Canavan disease, a genetic disease caused by an enzymatic deficiency, was the first to be approved. Three gene transfer paradigms for Parkinson's disease have been explored: converting L-dopa into dopamine through AADC gene delivery in the putamen; synthesizing GABA through GAD gene delivery in the overactive subthalamic nucleus and providing neurotrophic support through neurturin gene delivery in the nigro-striatal pathway. These pioneer clinical trials demonstrated the safety and tolerability of rAAV delivery in the human brain at moderate doses. Therapeutic effects however, were modest, emphasizing the need for higher doses of the therapeutic transgene product which could be achieved using more efficient vectors or expression cassettes. This will require re-addressing pharmacological aspects, with attention to which cases require either localized and cell-type specific expression or efficient brain-wide transgene expression, and when it is necessary to modulate or terminate the administration of transgene product. The ongoing development of targeted and regulated rAAV vectors is described.

An active contour-based atlas registration model applied to automatic subthalamic nucleus targeting on MRI: method and validation.

This paper presents a new non parametric atlas registration framework, derived from the optical flow model and the active contour theory, applied to automatic subthalamic nucleus (STN) targeting in deep brain stimulation (DBS) surgery. In a previous work, we demonstrated that the STN position can be predicted based on the position of surrounding visible structures, namely the lateral and third ventricles. A STN targeting process can thus be obtained by registering these structures of interest between a brain atlas and the patient image. Here we aim to improve the results of the state of the art targeting methods and at the same time to reduce the computational time. Our simultaneous segmentation and registration model shows mean STN localization errors statistically similar to the most performing registration algorithms tested so far and to the targeting expert's variability. Moreover, the computational time of our registration method is much lower, which is a worthwhile improvement from a clinical point of view.

Excitotoxicity-induced endocytosis confers drug targeting in cerebral ischemia.

OBJECTIVE: Targeting neuroprotectants specifically to the cells that need them is a major goal in biomedical research. Many peptidic protectants contain an active sequence linked to a carrier such as the transactivator of transcription (TAT) transduction sequence, and here we test the hypothesis that TAT-linked peptides are selectively endocytosed into neurons stressed by excitotoxicity and focal cerebral ischemia. METHODS: In vivo experiments involved intracerebroventricular injection of TAT peptides or conventional tracers (peroxidase, fluorescein isothiocyanate-dextran) in young rats exposed to occlusion of the middle cerebral artery at postnatal day 12. Cellular mechanisms of uptake were analyzed in dissociated cortical neuronal cultures. RESULTS: In both models, all tracers were taken up selectively into stressed neurons by endocytosis. In the in vivo model, this was neuron specific and limited to the ischemic area, where the neurons displayed enhanced immunolabeling for early endosomal antigen-1 and clathrin. The highly efficient uptake of TAT peptides occurred by the same selective mechanism as for conventional tracers. All tracers were targeted to the nucleus and cytoplasm of neurons that appeared viable, although ultimately destined to die. In dissociated cortical neuronal cultures, an excitotoxic dose of N-methyl-D-aspartate induced a similar endocytosis. It was 100 times more efficient with TAT peptides than with dextran, because the former bound to heparan sulfate proteoglycans at the cell surface, but it depended on dynamin and clathrin in both cases. INTERPRETATION: Excitotoxicity-induced endocytosis is the main entry route for protective TAT peptides and targets selectively the neurons that need to be protected.

Targeting Notch signaling in pancreatic cancer.

IMPORTANCE OF THE FIELD: With some 220,000 new cases/year in the world, pancreatic adenocarcinoma is the fourth highest cause of death by cancers. Among newly diagnosed patients about 210,000 will die within 9 months following diagnosis. Therefore, effective adjuncts to current treatment strategies are necessary. Because embryological signaling pathways are upregulated in pancreatic adenocarcinoma, they represent potential targets for future therapies. AREAS COVERED IN THIS REVIEW: Our aim is to present the Notch pathway, and to describe its involvement in pancreatic pathophysiology/carcinogenesis. This pathway appeared as a prime target for pancreatic cancer therapy. In the light of the crosstalk of Notch with other survival/embryologic pathways, drugs affecting more than one pathway may have to be combined. WHAT THE READER WILL GAIN: Drugs against gamma-secretases could thus serve in cancer treatment and can be combined with drugs targeting survival pathways interplaying with Notch such as Hedgehog. TAKE HOME MESSAGE: Downregulation of Notch contributes to the inhibition and apoptosis of pancreatic cancer cells whereas Hedgehog inhibition will allow for enhanced delivery of drugs to the tumor. Both pathway inhibitors appear to have synergistic effects for future therapeutics for pancreatic adenocarcinoma, once safety issues of compounds are overcome.

Protection from lethal Gram-negative bacterial sepsis by targeting Toll-like receptor 4

Rapport de synthèse : L'immunité innée regroupe les mécanismes moléculaires et cellulaires formant la première ligne de défense contre les infections microbiennes. La détection des micro-organismes pathogènes est assurée par des cellules sentinelles (cellules dendritiques et macrophages) qui jouent un rôle fondamental dans l'initiation des mécanismes de défense de l'hôte. Au contact de produits microbiens, ces cellules produisent un large échantillonnage de molécules, dont des cytokines, impliquées dans le développement de la réponse inflammatoire. La régulation de cette réponse relève d'un équilibre délicat, son insuffisance tant que son excès pouvant compromettre le devenir des patients infectés. La sepsis sévère et le choc septique représentent les formes les plus sévères d'infection, et leur mortalité demeure élevée (25 à 30% pour la sepsis sévère et 50 à 60% pour le choc septique). De plus, l'incidence de la sepsis tend à augmenter, atteignant en 2000 plus de 240 cas pour 100'000 personnes en Grande-Bretagne. La sepsis est caractérisée dans sa phase aiguë par une réponse inflammatoire exubérante. La plupart des thérapies visant à la bloquer ont toutefois montré des bénéfices incertains lors de leur application clinique. Il est donc impératif d'identifier de nouvelles cibles thérapeutiques. Les "Toll-like receptors" (TLRs) sont une famille de récepteurs qui jouent un rôle fondamental dans la détection des micro-organismes par les cellules du système immunitaire inné. Parmi eux, TLR4 est indispensable à la reconnaissance du lipopolysaccharide (LPS) des bactéries Gram-négatives. L'interaction entre TLR4 et le LPS représentant un élément précoce de la réponse de l'hôte à l'infection, nous avons émit l'hypothèse que TLR4 pourrait représenter une cible de choix en vue du développement de nouvelles thérapies contre la sepsis. Dans l'objectif de valider ce concept, nous avons, dans un premier temps, démontré que des souris génétiquement déficientes en TLR4 étaient totalement résistantes au choc septique induit par Escherichia coli (E. coli), une bactérie Gram-négative fréquemment responsable de sepsis. Forts de cette observation, nous avons développé une molécule recombinante composée du domaine extracellulaire de TLR4 fusionné à la partie IgGi-Fc. Cette molécule soluble, qui inhibait la réponse des macrophages au LPS in vitro, a été utilisée pour générer des anticorps anti-TLR4 chez le lapin. La spécificité et l'efficacité de ces anticorps ont été prouvées en démontrant que les anti-TLR4 bloquaient les signaux d'activation intracellulaire et la production de TNF et d'IL-6 en réponse au LPS et aux bactéries Gram-négatives in vitro et in vivo. Enfin, l'efficacité des ces anticorps a été testée dans des modèles de sepsis chez la souris. Ainsi, l'injection prophylactique (-lh) ou thérapeutique (+3h) d'anticorps anti-TLR4 réduisait la production de TNF et protégeait les animaux de la mort. De manière spectaculaire, ces anticorps réduisaient également la production de TNF et protégeaient de la sepsis à E. coli lorsqu'ils étaient administrés de manière prophylactique (-4h) et thérapeutique, jusqu'à 13 heures après l'initiation de l'infection. Ces résultats indiquent donc qu'il est possible de bloquer le développement de la réponse inflammatoire et de protéger du choc septique à bactéries Gram-négatives en utilisant des thérapies ciblant TLR4. Par ailleurs, ils suggèrent qu'une fenêtre d'opportunité de plusieurs heures pourrait être mise à profit pour initier un traitement chez les patients septiques. Ces résultats devraient encourager la poursuite des essais cliniques en cours qui visent à tester l'efficacité de thérapies dirigées contre TLR4 comme traitement complémentaire de la sepsis.

Targeting Cancer Stem-like Cells as an Approach to Defeating Cellular Heterogeneity in Ewing Sarcoma.

Plasticity in cancer stem-like cells (CSC) may provide a key basis for cancer heterogeneity and therapeutic response. In this study, we assessed the effect of combining a drug that abrogates CSC properties with standard-of-care therapy in a Ewing sarcoma family tumor (ESFT). Emergence of CSC in this setting has been shown to arise from a defect in TARBP2-dependent microRNA maturation, which can be corrected by exposure to the fluoroquinolone enoxacin. In the present work, primary ESFT from four patients containing CD133(+) CSC subpopulations ranging from 3% to 17% of total tumor cells were subjected to treatment with enoxacin, doxorubicin, or both drugs. Primary ESFT CSC and bulk tumor cells displayed divergent responses to standard-of-care chemotherapy and enoxacin. Doxorubicin, which targets the tumor bulk, displayed toxicity toward primary adherent ESFT cells in culture but not to CSC-enriched ESFT spheres. Conversely, enoxacin, which enhances miRNA maturation by stimulating TARBP2 function, induced apoptosis but only in ESFT spheres. In combination, the two drugs markedly depleted CSCs and strongly reduced primary ESFTs in xenograft assays. Our results identify a potentially attractive therapeutic strategy for ESFT that combines mechanism-based targeting of CSC using a low-toxicity antibiotic with a standard-of-care cytotoxic drug, offering immediate applications for clinical evaluation.

Conditional gene targeting of the ENaC subunit genes Scnn1b and Scnn1g.

Epithelial sodium channels (ENaC) are members of the degenerin/ENaC superfamily of non-voltage-gated, highly amiloride-sensitive cation channels that are composed of three subunits (alpha-, beta-, and gamma-ENaC). Since complete gene inactivation of the beta- and gamma-ENaC subunit genes (Scnn1b and Scnn1g) leads to early postnatal death, we generated conditional alleles and obtained mice harboring floxed and null alleles for both gene loci. Using quantitative RT-PCR analysis, we showed that the introduction of the loxP sites did not interfere with the mRNA transcript expression level of the Scnn1b and Scnn1g gene locus, respectively. Upon a regular and salt-deficient diet, both beta- and gamma-ENaC floxed mice showed no difference in their mRNA transcript expression levels, plasma electrolytes, and aldosterone concentrations as well as weight changes compared with control animals. These mice can now be utilized to dissect the role of ENaC function in classical and nonclassic target organs/tissues.

Targeting receptor activator of nuclear factor-kappa B as a new therapy for bone metastasis in non-small cell lung cancer.

PURPOSE OF REVIEW: The review aims at comprehensively discussing our current knowledge on bone metastases incidence in non-small cell lung cancer (NSCLC), their related complications as well as clinical impact in patients suffering from advanced disease. RECENT FINDINGS: After evoking the use of zoledronic acid as the established standard of care until recently, the new class of drugs available to prevent skeletal related events and targeting receptor activator of nuclear factor-kappa B (RANK) will be emphasized, reporting on denosumab clinical trials, a RANK-ligand (RANKL) targeting monoclonal antibody. Biological hypothesis regarding their mechanisms of action as well a potential direct impact on tumor cells are described according to the most recent laboratory as well as hypothesis-generating clinical data. SUMMARY: Targeting the RANK pathway is an efficient way to prevent complications of bone metastases in NSCLC. Interesting additional direct effects on tumor biology and evolution are being analyzed and prospectively assessed in clinical trials.

Transition from hemifusion to pore opening is rate limiting for vacuole membrane fusion.

Fusion pore opening and expansion are considered the most energy-demanding steps in viral fusion. Whether this also applies to soluble N-ethyl-maleimide sensitive fusion protein attachment protein receptor (SNARE)- and Rab-dependent fusion events has been unknown. We have addressed the problem by characterizing the effects of lysophosphatidylcholine (LPC) and other late-stage inhibitors on lipid mixing and pore opening during vacuole fusion. LPC inhibits fusion by inducing positive curvature in the bilayer and changing its biophysical properties. The LPC block reversibly prevented formation of the hemifusion intermediate that allows lipid, but not content, mixing. Transition from hemifusion to pore opening was sensitive to guanosine-5'-(gamma-thio)triphosphate. It required the vacuolar adenosine triphosphatase V0 sector and coincided with its transformation. Pore opening was rate limiting for the reaction. As with viral fusion, opening the fusion pore may be the most energy-demanding step for intracellular, SNARE-dependent fusion reactions, suggesting that fundamental aspects of lipid mixing and pore opening are related for both systems.

Targeting endoplasmic reticulum signaling pathways in cancer.

The endoplasmic reticulum (ER) orchestrates the production of membrane-bound and secreted proteins. However, its capacity to process the synthesis and folding of protein is limited. Protein overload and the accumulation of misfolded proteins in the ER trigger an adaptive response known as the ER-stress response that is mediated by specific ER-anchored signaling pathways. This response regulates cell functions aimed at restoring cellular homeostasis or at promoting apoptosis of irreparably damaged cells. Activation or deregulation of ER-signaling pathways has been associated with various diseases including cancer. Here we discuss how tumors engage ER-signaling pathways to promote tumorigenesis and how manipulation of this process by anticancer drugs may contribute to cancer treatment.

Caveolin-1 opens endothelial cell junctions by targeting catenins.

AIMS: A fundamental phenomenon in inflammation is the loss of endothelial barrier function, in which the opening of endothelial cell junctions plays a central role. However, the molecular mechanisms that ultimately open the cell junctions are largely unknown.¦METHODS AND RESULTS: Impedance spectroscopy, biochemistry, and morphology were used to investigate the role of caveolin-1 in the regulation of thrombin-induced opening of cell junctions in cultured human and mouse endothelial cells. Here, we demonstrate that the vascular endothelial (VE) cadherin/catenin complex targets caveolin-1 to endothelial cell junctions. Association of caveolin-1 with VE-cadherin/catenin complexes is essential for the barrier function decrease in response to the pro-inflammatory mediator thrombin, which causes a reorganization of the complex in a rope ladder-like pattern accompanied by a loss of junction-associated actin filaments. Mechanistically, we show that in response to thrombin stimulation the protease-activated receptor 1 (PAR-1) causes phosphorylation of caveolin-1, which increasingly associates with β- and γ-catenin. Consequently, the association of β- and γ-catenin with VE-cadherin is weakened, thus allowing junction reorganization and a decrease in barrier function. Thrombin-induced opening of cell junctions is lost in caveolin-1-knockout endothelial cells and after expression of a Y/F-caveolin-1 mutant but is completely reconstituted after expression of wild-type caveolin-1.¦CONCLUSION: Our results highlight the pivotal role of caveolin-1 in VE-cadherin-mediated cell adhesion via catenins and, in turn, in barrier function regulation.

Targeting PI3KC2β Impairs Proliferation and Survival in Acute Leukemia, Brain Tumours and Neuroendocrine Tumours.

BACKGROUND: Eight human catalytic phosphoinositide 3-kinase (PI3K) isoforms exist which are subdivided into three classes. While class I isoforms have been well-studied in cancer, little is known about the functions of class II PI3Ks. MATERIALS AND METHODS: The expression pattern and functions of the class II PI3KC2β isoform were investigated in a panel of tumour samples and cell lines. RESULTS: Overexpression of PI3KC2β was found in subsets of tumours and cell lines from acute myeloid leukemia (AML), glioblastoma multiforme (GBM), medulloblastoma (MB), neuroblastoma (NB), and small cell lung cancer (SCLC). Specific pharmacological inhibitors of PI3KC2β or RNA interference impaired proliferation of a panel of human cancer cell lines and primary cultures. Inhibition of PI3KC2β also induced apoptosis and sensitised the cancer cells to chemotherapeutic agents. CONCLUSION: Together, these data show that PI3KC2β contributes to proliferation and survival in AML, brain tumours and neuroendocrine tumours, and may represent a novel target in these malignancies.

Nanomedicines for active targeting: physico-chemical characterization of paclitaxel-loaded anti-HER2 immunonanoparticles and in vitro functional studies on target cells.

Paclitaxel (Tx)-loaded anti-HER2 immunonanoparticles (NPs-Tx-HER) were prepared by the covalent coupling of humanized monoclonal anti-HER2 antibodies (trastuzumab, Herceptin) to Tx-loaded poly (dl-lactic acid) nanoparticles (NPs-Tx) for the active targeting of tumor cells that overexpress HER2 receptors. The physico-chemical properties of NPs-Tx-HER were compared to unloaded immunonanoparticles (NPs-HER) to assess the influence of the drug on anti-HER2 coupling to the NP surface. The immunoreactivity of sulfo-MBS activated anti-HER2 mAbs and the in vitro efficacy of NPs-Tx-HER were tested on SKOV-3 ovarian cancer cells that overexpress HER2 antigens. Tx-loaded nanoparticles (NPs-Tx) obtained by a salting-out method had a size of 171+/-22 nm (P.I.=0.1) and an encapsulation efficiency of about of 78+/-10%, which corresponded to a drug loading of 7.8+/-0.8% (w/w). NPs-Tx were then thiolated and conjugated to activated anti-HER2 mAbs to obtain immunonanoparticles of 237+/-43 nm (P.I.=0.2). The influence of the activation step on the immunoreactivity of the mAbs was tested on SKOV-3 cells using 125I-radiolabeled mAbs, and the activity of the anti-HER2 mAbs was minimally affected after sulfo-MBS functionalization. Approximately 270 molecules of anti-HER2 mAbs were bound per nanoparticle. NPs-Tx-HER exhibited a zeta potential of 0.2+/-0.1 mV. The physico-chemical properties of the Tx-loaded immunonanoparticles were very similar to unloaded immunonanoparticles, suggesting that the encapsulation of the drug did not influence the coupling of the mAbs to the NPs. No drug loss was observed during the preparation process. DSC analysis showed that encapsulated Tx is in an amorphous or disordered-crystalline phase. These results suggest that Tx is entrapped in the polymeric matrix and not adsorbed to the surface of the NPs. In vitro studies on SKOV-3 ovarian cancer cells demonstrated the greater cytotoxic effect of NPs-Tx-HER compared to other Tx formulations. The results showed that at 1 ng Tx/ml, the viability of cells incubated with drug encapsulated in NP-Tx-HER was lower (77.32+/-5.48%) than the viability of cells incubated in NPs-Tx (97.4+/-12%), immunonanoparticles coated with Mabthera, as irrelevant mAb (NPs-Tx-RIT) (93.8+/-12%) or free drug (92.3+/-9.3%).