| 17015905 |
Bispecific antibody pretargeting PET (immunoPET) with an 124I-labeled hapten-peptide |
None |
J Nucl Med |
Bispecific antibody pretargeting PET (immunoPET) with an 124I-labeled hapten-peptide
Abstract
- We previously described a highly flexible bispecific antibody (bs-mAb) pretargeting procedure using a multivalent, recombinant anti-CEA (carcinoembryonic antigen) x anti-HSG (histamine-succinyl-glycine) fusion protein with peptides radiolabeled with 111In, 90Y, 177Lu, and 99mTc. The objective of this study was to develop a radioiodination procedure primarily to assess PET imaging with 124I.
A new peptide, DOTA-D-Tyr-D-Lys(HSG)-D-Glu-D-Lys(HSG)-NH2 (DOTA is 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid), was synthesized and conditions were established for radioiodination with yields of approximately 70% for 131I and 60% for 124I. Pretargeting with the 131I- and 124I-labeled peptide was tested in nude mice bearing LS174T human colonic tumors that were first given the anti-CEA x anti-HSG bs-mAb. Imaging (including small-animal PET) and necropsy data were collected at several intervals over 24 h. Comparisons were made between animals given 124I-anti-CEA Fab', 18F-FDG, the same peptide radiolabeled with 111In and pretargeted with the bs-mAb, and the radioiodinated peptide alone.
The radioiodinated peptide alone cleared quickly from the blood with no evidence of tumor targeting, but when pretargeted with the bs-mAb, tumor uptake increased 70-fold, with efficient and rapid clearance from normal tissues, allowing clear visualization of tumor within 1-2 h. Tumor uptake measured at necropsy was 3- to 15-fold higher and tumor-to-blood ratios were 10- to 20-fold higher than those for 124I-Fab' at 1 and 24 h, respectively. Thyroid and stomach uptake was observed with the radioiodinated peptide several hours after injection (animals were not premedicated to reduce uptake in these tissues), but gastric uptake was much more pronounced with 124I-Fab'. Tumor visualization with 18F-FDG at approximately 1.5 h was also good but showed substantially more uptake in several normal tissues, making image interpretation in the pretargeted animals less ambiguous than with 18F-FDG.
Bispecific antibody pretargeting has a significant advantage for tumor imaging over directly radiolabeled antibodies and could provide additional enhancements for oncologic imaging, particularly for improving targeting specificity as compared with 18F-FDG.
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| 17016423 |
Drugs, their targets and the nature and number of drug targets |
10.1038/nrd2132. |
Nat Rev Drug Discov |
Drugs, their targets and the nature and number of drug targets
Abstract
- What is a drug target? And how many such targets are there? Here, we consider the nature of drug targets, and by classifying known drug substances on the basis of the discussed principles we provide an estimation of the total number of current drug targets.
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| 17021057 |
Determination of MICs of aminocandin for Candida spp. and filamentous fungi |
10.1128/JCM.01550-06. |
J Clin Microbiol |
Determination of MICs of aminocandin for Candida spp. and filamentous fungi
Abstract
- Candida and Aspergillus spp., as well as other filamentous molds, have increasingly been reported as the causes of severe invasive fungal infections. We evaluated the new echinocandin aminocandin (AMN) for its antifungal activities against a range of fungal pathogens by determination of the MICs for the organisms. The MICs of the comparator drugs amphotericin B, caspofungin, micafungin, and voriconazole were also determined. The MICs of AMN for 25 strains each of non-Candida albicans Candida spp. (including Candida parapsilosis, Candida krusei, Candida guilliermondii, and Candida tropicalis), Aspergillus fumigatus, Scedosporium spp., Fusarium spp., and zygomycetes (including Absidia, Mucor, and Rhizopus spp.) were determined by using the Clinical and Laboratory Standards Institute M27-A2 and M38-A methodologies for yeasts and filamentous molds, respectively. The MIC ranges of AMN for all yeasts were similar (0.03 to 4.0 microg/ml), while the MIC ranges of AMN for filamentous fungi were species specific. AMN demonstrated potent antifungal activity against A. fumigatus, limited activity against Scedosporium spp., and no activity against zygomycetes or Fusarium spp. Our data showed that AMN demonstrated potent antifungal activities against all of the yeasts and Aspergillus isolates tested, suggesting that AMN could be an important addition to our arsenal of antifungals for the treatment of invasive fungal disease.
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| 17028183 |
Crystal structure of the Mycobacterium tuberculosis P450 CYP121- fluconazole complex reveals new azole drug-P450 binding mode. |
10.1074/jbc.m607665200 |
J. Biol. Chem. |
Crystal structure of the Mycobacterium tuberculosis P450 CYP121- fluconazole complex reveals new azole drug-P450 binding mode.
Abstract
- Azole and triazole drugs are cytochrome P450 inhibitors widely used as fungal antibiotics and possessing potent antimycobacterial activity. We present here the crystal structure of Mycobacterium tuberculosis cytochrome P450 CYP121 in complex with the triazole drug fluconazole, revealing a new azole heme ligation mode. In contrast to other structurally characterized cytochrome P450 azole complexes, where the azole nitrogen directly coordinates the heme iron, in CYP121 fluconazole does not displace the aqua sixth heme ligand but occupies a position that allows formation of a direct hydrogen bond to the aqua sixth heme ligand. Direct ligation of fluconazole to the heme iron is observed in a minority of CYP121 molecules, albeit with severe deviations from ideal geometry due to close contacts with active site residues. Analysis of both ligand-on and -off structures reveals the relative position of active site residues derived from the I-helix is a key determinant in the relative ratio of on and off states. Regardless, both ligand-bound states lead to P450 inactivation by active site occlusion. This previously unrecognized means of P450 inactivation is consistent with spectroscopic analyses in both solution and in the crystalline form and raises important questions relating to interaction of azoles with both pathogen and human P450s.
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| 17041104 |
Sensitization of B16 tumor cells with a CXCR4 antagonist increases the efficacy of immunotherapy for established lung metastases |
10.1158/1535-7163.MCT-06-0310. |
Mol Cancer Ther |
Sensitization of B16 tumor cells with a CXCR4 antagonist increases the efficacy of immunotherapy for established lung metastases
Abstract
- Expression of the chemokine receptor CXCR4 by tumor cells promotes metastasis, possibly by activating prosurvival signals that render cancer cells resistant to immune attack. Inhibition of CXCR4 with a peptide antagonist, T22, blocks metastatic implantation of CXCR4-transduced B16 (CXCR4-luc-B16) melanoma cells in lung, but not the outgrowth of established metastases, raising the question of how T22 can best be used in a clinical setting. Herein, whereas the treatment of CXCR4-luc-B16 cells in vitro with the CXCR4 ligand CXCL12 did not reduce killing induced by cisplatin or cyclophosphamide, CXCL12 markedly reduced Fas-dependent killing by gp100-specific (pmel-1) CD8(+) T cells. T22 pretreatment restored sensitivity of CXCR4-luc-B16 cells to pmel-1 killing, even in the presence of CXCL12. Two immune-augmenting regimens were used in combination with T22 to treat experimental lung metastases. First, low-dose cyclophosphamide treatment (100 mg/kg) on day 5 in combination with T22 (days 4-7) yielded a approximately 70% reduction of B16 metastatic tumor burden in the lungs compared with cyclophosphamide treatment alone (P < 0.001). Furthermore, whereas anti-CTL antigen 4 (CTLA4) monoclonal antibody (mAb; or T22 treatment) alone had little effect on established B16 metastases, pretreatment with T22 (in combination with anti-CTLA4 mAb) resulted in a 50% reduction in lung tumor burden (P = 0.02). Thus, in vitro, CXCR4 antagonism with T22 renders B16 cells susceptible to killing by antigen-specific T cells. In vivo, T22 synergizes with cyclophosphamide or anti-CTLA4 mAb in the treatment of established lung metastases, suggesting a novel strategy for augmenting the efficacy of immunotherapy.
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| 17042781 |
Characterization of novel M-superfamily conotoxins with new disulfide linkage |
10.1111/j.1742-4658.2006.05493.x. |
FEBS J |
Characterization of novel M-superfamily conotoxins with new disulfide linkage
Abstract
- The M-superfamily with the typical Cys framework (-CC-C-C-CC-) is one of the seven major superfamilies of conotoxins found in the venom of cone snails. Based on the number of residues in the last Cys loop (between C4 and C5), M-superfamily conotoxins can be provisionally categorized into four branches (M-1, M-2, M-3, M-4) [Corpuz GP, Jacobsen RB, Jimenez EC, Watkins M, Walker C, Colledge C, Garrett JE, McDougal O, Li W, Gray WR, et al. (2005) Biochemistry44, 8176-8186]. Here we report the purification of seven M-superfamily conotoxins from Conus marmoreus (five are novel and two are known as mr3a and mr3b) and one known M-1 toxin tx3a from Conus textile. In addition, six novel cDNA sequences of M-superfamily conotoxins have been identified from C. marmoreus, Conus leopardus and Conus quercinus. Most of the above novel conotoxins belong to M-1 and M-2 and only one to M-3. The disulfide analyses of two M-1 conotoxins, mr3e and tx3a, revealed that they possess a new disulfide bond arrangement (C1-C5, C2-C4, C3-C6) which is different from those of the M-4 branch (C1-C4, C2-C5, C3-C6) and M-2 branch (C1-C6, C2-C4, C3-C5). This newly characterized disulfide connectivity was confirmed by comparing the HPLC profiles of native mr3e and its two regioselectively folded isoforms. This is the first report of three different patterns of disulfide connectivity in conotoxins with the same cysteine framework.
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| 17051221 |
Structures of human insulin-degrading enzyme reveal a new substrate recognition mechanism. |
10.1038/nature05143 |
Nature |
Structures of human insulin-degrading enzyme reveal a new substrate recognition mechanism.
Abstract
- Insulin-degrading enzyme (IDE), a Zn2+-metalloprotease, is involved in the clearance of insulin and amyloid-beta (refs 1-3). Loss-of-function mutations of IDE in rodents cause glucose intolerance and cerebral accumulation of amyloid-beta, whereas enhanced IDE activity effectively reduces brain amyloid-beta (refs 4-7). Here we report structures of human IDE in complex with four substrates (insulin B chain, amyloid-beta peptide (1-40), amylin and glucagon). The amino- and carboxy-terminal domains of IDE (IDE-N and IDE-C, respectively) form an enclosed cage just large enough to encapsulate insulin. Extensive contacts between IDE-N and IDE-C keep the degradation chamber of IDE inaccessible to substrates. Repositioning of the IDE domains enables substrate access to the catalytic cavity. IDE uses size and charge distribution of the substrate-binding cavity selectively to entrap structurally diverse polypeptides. The enclosed substrate undergoes conformational changes to form beta-sheets with two discrete regions of IDE for its degradation. Consistent with this model, mutations disrupting the contacts between IDE-N and IDE-C increase IDE catalytic activity 40-fold. The molecular basis for substrate recognition and allosteric regulation of IDE could aid in designing IDE-based therapies to control cerebral amyloid-beta and blood sugar concentrations.
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| 17055432 |
Insulin degrading enzyme is a cellular receptor mediating varicella-zoster virus infection and cell-to-cell spread. |
10.1016/j.cell.2006.08.046 |
Cell |
Insulin degrading enzyme is a cellular receptor mediating varicella-zoster virus infection and cell-to-cell spread.
Abstract
- Varicella-zoster virus (VZV) causes chickenpox and shingles. While varicella is likely spread as cell-free virus to susceptible hosts, the virus is transmitted by cell-to-cell spread in the body and in vitro. Since VZV glycoprotein E (gE) is essential for virus infection, we postulated that gE binds to a cellular receptor. We found that insulin-degrading enzyme (IDE) interacts with gE through its extracellular domain. Downregulation of IDE by siRNA, or blocking of IDE with antibody, with soluble IDE protein extracted from liver, or with bacitracin inhibited VZV infection. Cell-to-cell spread of virus was also impaired by blocking IDE. Transfection of cell lines impaired for VZV infection with a plasmid expressing human IDE resulted in increased entry and enhanced infection with cell-free and cell-associated virus. These studies indicate that IDE is a cellular receptor for both cell-free and cell-associated VZV.
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| 17056832 |
The in vitro effects of a novel vascular protectant, AGI-1067, on platelet aggregation and major receptor expression in subjects with multiple risk factors for vascular disease |
10.1177/1074248406290598. |
J Cardiovasc Pharmacol Ther |
The in vitro effects of a novel vascular protectant, AGI-1067, on platelet aggregation and major receptor expression in subjects with multiple risk factors for vascular disease
Abstract
- Oxidation-sensitive signals are important in platelet activation. The novel, phenolic, intracellular and extra-cellular antioxidant AGI-1067 inhibits the expression of a number of proinflammatory genes involved in atherosclerosis. The effect of AGI-1067 on human platelets was evaluated. Blood obtained from 20 aspirin-naïve volunteers with multiple risk factors for vascular disease was preincubated with escalating concentrations of AGI-1067 for the assessment of its ex vivo effects on platelet aggregation and expression of major surface receptors flow cytometry, evaluated by flow cytometry. AGI-1067 resulted in significant inhibition of a variety of activation-dependent platelet biomarkers in healthy volunteers, including adenosine diphosphate-induced platelet aggregation and decreased surface platelet expression of glycoprotein IIb/IIIa antigen, activity with PAC-1 antibody, and glycoprotein Ib (CD42b). The effect of AGI-1067 differs from other known antiplatelet agents, suggesting opportunities for therapeutic combination. These data need to be confirmed in subjects receiving orally dosed AGI-1067 to be clinically relevant.
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| 17063408 |
Chemical deterrence of a cyanobacterial metabolite against generalized and specialized grazers |
10.1007/s10886-006-9212-y. |
J Chem Ecol |
Chemical deterrence of a cyanobacterial metabolite against generalized and specialized grazers
Abstract
- Pitipeptolide A is the major secondary metabolite in a persistent population of the cyanobacterium Lyngbya majuscula from Guam. Because this cyanobacterium is of low preference to many sympatric consumers, we tested the hypothesis that this compound acted as a chemical defense. Pitipeptolide A was deterrent to urchins, two species of amphipods, and small herbivorous crabs, whereas it did not deter feeding by the sea hare Stylocheilus striatus, which readily consumes cyanobacteria. Although our comparison included various small invertebrates, which are often tolerant to algal chemical defenses, this cyanobacterial compound proved deterrent at natural concentrations to all but one of the consumer species tested. Thus, the production of defensive secondary metabolites is likely related to the common occurrence of L. majuscula on this coral reef despite the abundance of diverse grazers.
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| 17064074 |
Cyclic MrIA: a stable and potent cyclic conotoxin with a novel topological fold that targets the norepinephrine transporter |
10.1021/jm060299h. |
J Med Chem |
Cyclic MrIA: a stable and potent cyclic conotoxin with a novel topological fold that targets the norepinephrine transporter
Abstract
- Conotoxins, disulfide-rich peptides from the venom of cone snails, have created much excitement over recent years due to their potency and specificity for ion channels and their therapeutic potential. One recently identified conotoxin, MrIA, a 13-residue member of the chi-conotoxin family, inhibits the human norepinephrine transporter (NET) and has potential applications in the treatment of pain. In the current study, we show that the beta-hairpin structure of native MrIA is retained in a synthetic cyclic version, as is biological activity at the NET. Furthermore, the cyclic version has increased resistance to trypsin digestion relative to the native peptide, an intriguing result because the cleavage site for the trypsin is not close to the cyclization site. The use of peptides as drugs is generally hampered by susceptibility to proteolysis, and so, the increase in enzymatic stability against trypsin observed in the current study may be useful in improving the therapeutic potential of MrIA. Furthermore, the structure reported here for cyclic MrIA represents a new topology among a growing number of circular disulfide-rich peptides.
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| 17067157 |
Integerrimides A and B, cyclic heptapeptides from the latex of Jatropha integerrima |
10.1021/np0602012. |
J Nat Prod |
Integerrimides A and B, cyclic heptapeptides from the latex of Jatropha integerrima
Abstract
- Two new cyclic heptapeptides, integerrimides A and B, have been isolated from the latex of Jatropha integerrima. Their structures were elucidated by using extensive 1D and 2D NMR, MS, and chemical degradation. At 50 microM both peptides 1 and 2 significantly inhibited neurite outgrowth in neuronal cell culture. They also partially inhibited proliferation of human IPC-298 melanoma cells as well as migration of human Capan II pancreatic carcinoma cells, but were inactive in HSV-1, antifungal, and antimalarial assays.
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| 17067166 |
Chrysosporide, a cyclic pentapeptide from a New Zealand sample of the fungus Sepedonium chrysospermum |
10.1021/np060137o. |
J Nat Prod |
Chrysosporide, a cyclic pentapeptide from a New Zealand sample of the fungus Sepedonium chrysospermum
Abstract
- A new cyclic pentapeptide, chrysosporide (1), was isolated from a New Zealand sample of the mycoparasitic fungus Sepedonium chrysospermum by bioactivity-guided fractionation. The planar structure was deduced by detailed spectroscopic analysis, and the absolute configurations of the amino acid residues were defined by Marfey's method. As both enantiomers of Leu occurred in chrysosporide, molecular mechanics calculations were applied to the analysis to distinguish between the possible structural isomers. Only the lowest energy conformers of the cyclo-(L-Val-D-Ala-L-Leu-L-Leu-D-Leu) isomer were in agreement with the observed NOEs, suggesting that this was the most probable amino acid sequence for chrysosporide (1).
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| 17080685 |
Isolation and identification of the icosalides--cyclic peptolides with selective antibiotic and cytotoxic activities |
10.1038/ja.2006.68. |
J Antibiot (Tokyo) |
Isolation and identification of the icosalides--cyclic peptolides with selective antibiotic and cytotoxic activities
Abstract
- Three cyclic peptolides have been isolated from two different fungal species and their structures determined. Icosalides A1 (1a), A2 (1b), and B (1c) each contain two serine and two leucine amino acid residues and incorporate two fatty acid moieties as part of the central twenty-member ring. 1a contains L-serine and both D- and L-leucine residues, while 1b and 1c contain only L-amino acid residues. Icosalide A1 displays antimicrobial activity against Streptococcus pyogenes, S. pneumoniae (Felton), and Enterococcus faecalis. Icosalides A2 and B are cytotoxic to replicating MDCK cells.
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| 17080686 |
Cylindrocyclin A, a new cytotoxic cyclopeptide from Cylindrocarpon sp |
10.1038/ja.2006.69. |
J Antibiot (Tokyo) |
Cylindrocyclin A, a new cytotoxic cyclopeptide from Cylindrocarpon sp
Abstract
- In the course of a screening of fungal extracts for new metabolites with cytotoxic activities cylindrocyclin A (1) was isolated. The producing strain was identified as Cylindrocarpon sp. by microscopy and ITS rDNA sequence analysis. 1 is a novel compound that exhibits cytotoxic acticity against six different cell lines with IC50 values ranging from 11 to 53 microM. 1 has no antibacterial or antifungal activity. The compound is a cyclic nonapeptide comprising three alanines, five leucines and one isoleucine. Four amino acids are N-methylated. Its structure was elucidated by spectroscopic methods.
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