Thioether analogues of disulfide-bridged cyclic peptides targeting death receptor 5: conformational analysis, dimerisation and consequences for receptor activation.

Cyclic peptides containing redox-stable thioether bridges might provide a useful alternative to disulfide-bridged bioactive peptides. We report the effect of replacing the disulfide bridge with a lanthionine linkage in a 16-mer cyclic peptide that binds to death receptor 5 (DR5, TRAIL-R2). Upon covalent oligomerisation, the disulfide-bridged peptide has previously shown similar behaviour to that of TNF-related apoptosis inducing ligand (TRAIL), by selectively triggering the DR5 cell death pathway. The structural and biological properties of the DR5-binding peptide and its desulfurised analogue were compared. Surface plasmon resonance (SPR) data suggest that these peptides bind DR5 with comparable affinities. The same holds true for dimeric versions of these peptides: the thioether is able to induce DR5-mediated apoptosis of BJAB lymphoma and tumorigenic BJELR cells, albeit to a slightly lower extent compared to its disulfide homologue. NMR analysis revealed subtle variation in the conformations of the two peptides and suggests that the thioether peptide is slightly less folded than its disulfide homologue. These observations could account for the different capability of the two dimers to cluster DR5 receptors on the cell surface and to trigger apoptosis. Nevertheless, our results suggest that the thioether peptide is a potential candidate for evaluation in animal models.

Cysteine-rich domain 1 of CD40 mediates receptor self-assembly.

The activation of CD40 on B cells, macrophages, and dendritic cells by its ligand CD154 (CD40L) is essential for the development of humoral and cellular immune responses. CD40L and other TNF superfamily ligands are noncovalent homotrimers, but the form under which CD40 exists in the absence of ligand remains to be elucidated. Here, we show that both cell surface-expressed and soluble CD40 self-assemble, most probably as noncovalent dimers. The cysteine-rich domain 1 (CRD1) of CD40 participated to dimerization and was also required for efficient receptor expression. Modelization of a CD40 dimer allowed the identification of lysine 29 in CRD1, whose mutation decreased CD40 self-interaction without affecting expression or response to ligand. When expressed alone, recombinant CD40-CRD1 bound CD40 with a K(D) of 0.6 µM. This molecule triggered expression of maturation markers on human dendritic cells and potentiated CD40L activity. These results suggest that CD40 self-assembly modulates signaling, possibly by maintaining the receptor in a quiescent state.

Multimerization of an apoptogenic TRAIL-mimicking peptide by using adamantane-based dendrons.

We have developed a straightforward strategy to multimerize an apoptogenic peptide that mimics the natural tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) by using adamantane-based dendrons as multivalent scaffolds. The selective binding affinity of the ligands to TRAIL receptor 2 (TR2) was studied by surface plasmon resonance, thus demonstrating that the trimeric and hexameric forms of the peptide exert an increased affinity of about 1500- and 20,000-fold, respectively, relative to the monomer. Moreover, only the trimeric and hexameric ligands were able to induce cell death in TR2 expressing cells (BJAB), thus confirming that a multivalent form of the peptide is necessary to trigger a substantial TR2-dependent apoptotic response in vitro. These results provide interesting insight into the multivalency effect on biological ligand/receptor interactions for future therapeutic applications.

Stabilized helical peptides: overview of the technologies and therapeutic promises.

INTRODUCTION: Helical structures in proteins and naturally occurring peptides play a major role in a variety of biological processes by mediating interactions with proteins and other macromolecules such as nucleic acids and lipid membranes. The use of short synthetic peptides encompassing helical segments to modulate or disrupt such interactions, when associated with human diseases, represents great pharmacological interest. AREAS COVERED: Multiple chemical approaches have been developed to increase the conformational and metabolic stabilities of helical peptides and to improve their biomedical potential. After a brief overview of these technologies and the most recent developments, this review will focus on the main therapeutic areas and targets and will discuss their promise. EXPERT OPINION: Potential benefits associated with increased helix stability extend beyond simple affinity enhancement. Some peptidomimetic helices are being endowed with features desirable for cellular activity such as increased resistance to proteolysis and/or cell permeability. Recent advances in the field of peptide and related peptidomimetic helices are not just conceptual, but are likely to be of practical utility in the process of optimizing peptides as clinical candidates, and developing medium-size therapeutics.

First Quantitative Imaging of Organic Fluorine within Angiogenic Tissues by Particle Induced Gamma-Ray Emission (PIGE) Analysis: First PIGE Organic Fluorine Imaging.

PET (Positron Emission Tomography) allows imaging of the in vivo distribution of biochemical compounds labeled with a radioactive tracer, mainly 18F-FDG (2-deoxy-2-[18F] fluoro-D-glucose). 18F only allows a relatively poor spatial resolution (2-3 mm) which does not allow imaging of small tumors or specific small size tissues, e.g. vasculature. Unfortunately, angiogenesis is a key process in various physiologic and pathologic processes and is, for instance, involved in modern anticancer approaches. Thus ability to visualize angiogenesis could allow early diagnosis and help to monitor the response of cancer to specific chemotherapies. Therefore, indirect analytical techniques are required to assess the localization of fluorinated compounds at a micrometric scale. Multimodality imaging approaches could provide accurate information on the metabolic activity of the target tissue. In this article, PIGE method (Particle Induced Gamma-ray Emission) was used to determine fluorinated tracers by the nuclear reaction of 19F(p,p'γ)19F in tissues. The feasibility of this approach was assessed on polyfluorinated model glucose compounds and novel peptide-based tracer designed for angiogenesis imaging. Our results describe the first mapping of the biodistribution of fluorinated compounds in both vascularized normal tissue and tumor tissue.

Comparative toxicity and efficacy of combined radioimmunotherapy and antiangiogenic therapy in carcinoembryonic antigen-expressing medullary thyroid cancer xenograft.

UNLABELLED: A significant antitumor effect was previously observed with radioimmunotherapy using anti-carcinoembryonic antigen (131)I-F6 monoclonal antibody in medullary thyroid cancer-bearing nude mice. Nevertheless, no complete response was observed. As seen with chemotherapy, drugs targeting the tumor microenvironment might improve radioimmunotherapy efficacy. This study evaluated the toxicity and efficacy of combining radioimmunotherapy with thalidomide or a cyclopeptidic vascular endothelial growth inhibitor (CBOP11) in mice grafted with the TT human medullary thyroid cancer cell line. METHODS: Six to 10 nude mice treated with 92.5 MBq of (131)I-F6 in association with 200 mg/kg/d of oral thalidomide during 20 d by force-feeding or 0.45 mg/kg/d of CBOP11 during 25 d using subcutaneous minipumps were compared with control mice receiving either treatment or naked F6 or nonspecific (131)I-734. Combined therapies included (131)I-F6 at day 0 followed by thalidomide between days 20 and 40, thalidomide between days 0 and 20 followed by (131)I-F6 at day 25, (131)I-F6 at day 0 and CBOP11 between days 0 and 25, CBOP11 between days 0 and 25 followed by (131)I-F6 at day 25, and (131)I-F6 at day 0 followed by CBOP11 between days 20 and 45. Animal weight, hematologic toxicity, tumor volume, and serum calcitonin were monitored for the following 3 mo. Improvement of (125)I-F6 tumor biodistribution by antiangiogenic drug was studied after pretreatment by thalidomide. Follow-up of the tumor after combined antiangiogenic and radioimmunotherapy therapies was performed by histology studies. RESULTS: Combined associations, as compared with radioimmunotherapy alone, increased leukopenia but not thrombocytopenia. Tumor volume-quadrupling time (TVQT) was 22.8 +/- 3.3 d in the control group, 29.9 +/- 3.6 d in the group treated with thalidomide, 34.6 +/- 4.4 d in the group treated with CBOP11, and 51.0 +/- 2.8 d after radioimmunotherapy alone. As compared with radioimmunotherapy, TVQT was significantly longer (P < 0.01) after thalidomide followed by radioimmunotherapy (69.83 +/- 3.9), CBOP11 followed by radioimmunotherapy (71.3 +/- 6.1), and CBOP11-radioimmunotherapy in concomitance (64.2 +/- 6.1). Nevertheless, TVQT was not increased after radioimmunotherapy followed by thalidomide (48.8 +/- 4) and radioimmunotherapy followed by CBOP11 (56.8 +/- 4.8). Surprisingly, pretreatment by CBOP11 or thalidomide sensitized larger tumors (>300 mm(3)) to radioimmunotherapy. Change in calcitonin levels confirmed morphologic tumor response. Tumor uptake 24 h after injection of (125)I-F6 was 4.5 +/- 0.6 percentage injected dose per gram (%ID/g) without pretreatment and 8.7 +/- 1.3 %ID/g with pretreatment by thalidomide. An increase of the antitumor effect observed using the antiangiogenic drug combined with radioimmunotherapy was correlated with a decrease of blood vessels shown by von Willebrand immunostaining. CONCLUSION: Pretreatment with antiangiogenic therapies improved radioimmunotherapy efficacy, with acceptable toxicity. Future investigations will be performed to understand how antiangiogenic agents sensitize large tumors to radioimmunotherapy.

Sonochemical approach to the synthesis of Fe(3)O(4)@SiO(2) core-shell nanoparticles with tunable properties.

In this study, we report a rapid sonochemical synthesis of monodisperse nonaggregated Fe(3)O(4)@SiO(2) magnetic nanoparticles (NPs). We found that coprecipitation of Fe(II) and Fe(III) in aqueous solutions under the effect of power ultrasound yields smaller Fe(3)O(4) NPs with a narrow size distribution (4-8 nm) compared to the silent reaction. Moreover, the coating of Fe(3)O(4) NPs with silica using an alkaline hydrolysis of tetraethyl orthosilicate in ethanol-water mixture is accelerated many-fold in the presence of a 20 kHz ultrasonic field. The thickness of the silica shell can be easily controlled in the range of several nanometers during sonication. Mossbauer spectra revealed that nonsuperparamagnetic behavior of obtained core-shell NPs is mostly related to the dipole-dipole interactions of magnetic cores and not to the particle size effect. Core-shell Fe(3)O(4)@SiO(2) NPs prepared with sonochemistry exhibit a higher magnetization value than that for NPs obtained under silent conditions owing to better control of the deposited silica quantities as well as to the high speed of sonochemical coating, which prevents the magnetite from oxidizing.

Analytical performances of FT-IR spectrometry and imaging for concentration measurements within biological fluids, cells, and tissues.

FT-IR spectrometry has proved to be a useful tool for determining a series of plasma molecular concentrations. Dedicated experiments were first performed to test the analytical performance that could be obtained by FT-IR spectrometry using a synthesized N3-peptide exhibiting a -N3 absorption centered at 2110 cm(-1), a spectral region where no organic material of biological samples absorbs. Further, we investigated whether this technology was able to allow quantification of metabolic parameters (glucose and lactic acid) within plasma, cells, and tissues as an alternative method to the "classical" biochemical approaches, which require sophisticated biological material treatment and expensive reagents. For this purpose we used a series of plasma samples to determine glucose and lactic acid concentrations, which are common markers of cancer growth. We compared the results of the main spectral data treatments commonly achieved for FT-IR data analysis, such as univariate (Beer-Lambert) or multivariate (PLS) calibrations, as well as the deconvolution of the spectral interval of interest (1200-900 cm(-1)). No significant differences were found regarding the analytical performances of these methods. Spectral deconvolution was finally undertaken on cultured and on xenografted cells (U87 glial cells implied in human gliomas) to determine glucose and lactic acid concentrations. In this case, qualification was allowed by FT-IR imaging on the cellular models since biochemical approaches are not efficient to reach metabolic concentrations at the cellular level while keeping tissue organization.

Design, synthesis, and evaluation of original carriers for targeting vascular endothelial growth factor receptor interactions.

PURPOSE: Angiogenesis is a key event in tumor growth and metastasis, chronic inflammatory disease, and cardiovascular disease. It is controlled by positive and negative regulators, which include vascular endothelial growth factor (VEGF) as the most active of these. VEGF/VEGF receptors are important targets not only for therapy but also for imaging. Based on the structural study of VEGF, we developed a novel cyclopeptide (cyclo-VEGI) that exhibits powerful antitumor properties. We herein report the design of novel molecules derived from cyclo-VEGI as potential targeting agents in cancer and other angiogenesis-related diseases. METHODS: We performed selective chemical modification of the most active VEGF-derived cyclopeptide (cyclo-VEGI). Original hydrophilic linkers were synthesized and coupled to cyclo-VEGI. These reactions provide nanocarriers for delivery. The inhibitory effect of the different compounds on VEGF binding was evaluated in competition assays with 125I-VEGF. A fluorescent cyclo-VEGI peptide was synthezised to assess direct binding and internalization of cyclo-VEGI. RESULTS: Chemical modifications of cyclo-VEGI do not diminish the biological activity of cyclo-VEGI as measured in competition assays; in fact, it is even increased. Moreover there is a strong cellular accumulation of the fluorescent-labeled cyclo-VEGI. Conjugates synthesized in this study may be useful leads to design delivery systems for targeting approaches in cancer and other angiogenesis-related diseases. CONCLUSION: The modified cyclo-VEGIs may have a wide range of applications and represent a useful tool to develop delivery/carrier systems for therapeutic targeting or imaging.

Structure and inhibitory effects on angiogenesis and tumor development of a new vascular endothelial growth inhibitor.

Blocking angiogenesis is an attractive strategy to inhibit tumor growth, invasion, and metastasis. We describe here the structure and the biological action of a new cyclic peptide derived from vascular endothelial growth factor (VEGF). This 17-amino acid molecule designated cyclopeptidic vascular endothelial growth inhibitor (cyclo-VEGI, CBO-P11) encompasses residues 79-93 of VEGF which are involved in the interaction with VEGF receptor-2. In aqueous solution, cyclo-VEGI presents a propensity to adopt a helix conformation that was largely unexpected because only beta-sheet structures or random coil conformations have been observed for macrocyclic peptides. Cyclo-VEGI inhibits binding of iodinated VEGF165 to endothelial cells, endothelial cells proliferation, migration, and signaling induced by VEGF165. This peptide also exhibits anti-angiogenic activity in vivo on the differentiated chicken chorioallantoic membrane. Furthermore, cyclo-VEGI significantly blocks the growth of established intracranial glioma in nude and syngeneic mice and improves survival without side effects. Taken together, these results suggest that cyclo-VEGI is an attractive candidate for the development of novel angiogenesis inhibitor molecules useful for the treatment of cancer and other angiogenesis-related diseases.

Synthesis and evaluation of organosilicon inhibitors of active purine transport in human osteoblasts.

In the search for new compounds that might, once incorporated into biomaterials, stimulate the natural processes of bone regeneration, a new series of silicon-containing alkyl nucleobase analogues has been synthesized. An active hypoxanthine transport process in human osteoblasts was demonstrated, with an apparent Michaelis constant of 2.3 microM and a maximum possible rate of 0.47 pmol s(-1) x 10(6) cell. The synthesized analogues were tested for toxicity in human osteoblasts. Nontoxic analogues were tested in competition transport studies with [(14)C]hypoxanthine. Two of them were found to inhibit the active transport of hypoxanthine in human osteoblasts, with IC(50) values of 6.5 and 11.6 microM.