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John H. Miller - One of the best experts on this subject based on the ideXlab platform.
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Preclinical Development Peloruside- and Laulimalide-Resistant Human Ovarian Carcinoma Cells Have bI-Tubulin Mutations and Altered Expression of bII- and bIII-Tubulin Isotypes
2016Co-Authors: Anja Wilmes, Ernest Hamel, Pisana Rawson, Bronwyn M. Kivell, Peter T. Northcote, Janet Crawford, Paraskevi Giannakakou, John H. MillerAbstract:Peloruside A and Laulimalide are potent microtubule-stabilizing natural products with a mechanism of action similar to that of paclitaxel. However, the binding site of peloruside A and Laulimalide on tubulin remains poorly understood. Drug resistance in anticancer treatment is a serious problem. We developed peloruside A- and Laulimalide-resistant cell lines by selecting 1A9 human ovarian carcinoma cells that were able to grow in the presence of one of these agents. The 1A9-Laulimalide resistant cells (L4) were 39-fold resistant to the selecting agent and 39-fold cross-resistant to peloruside A, whereas the 1A9-peloruside A resistant cells (R1) were 6-fold resistant to the selecting agent while they remained sensitive to Laulimalide. Neither cell line showed resistance to paclitaxel or other drugs that bind to the taxoid site on b-tubulin nor was there resistance to microtubule-destabilizing drugs. The resistant cells exhibited impaired peloruside A/ Laulimalide-induced tubulin polymerization and impaired mitotic arrest. Tubulin mutations were found in the bI-tubulin isotype, R306H or R306C for L4 and A296T for R1 cells. This is the first cell-based evidence to support a b-tubulin–binding site for peloruside A and Laulimalide. To determine whether the different resistance phenotypes of the cells were attributable to any other tubulin alterations, the b-tubulin isotype composition of the cells was examined. Increased expression of bII- and bIII-tubulin was observed in L4 cells only. These results provide insight into how alterations in tubulin lead to unique resistance profiles for two drugs, peloruside A and Laulimalide, that have a similar mode of action. Mol Cancer Ther; 10(8); 1–11. 2011 AACR
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Effect of taxoid and nontaxoid site microtubule‐stabilizing agents on axonal transport of mitochondria in untransfected and ECFP‐htau40‐transfected rat cortical neurons in culture
Journal of Neuroscience Research, 2014Co-Authors: Viswanath Das, Dalice A. Sim, John H. MillerAbstract:An important aspect of synaptic plasticity in the brain is axonal transport of essential components such as mitochondria from the soma to the synapse. For uninterrupted transport of cellular cargo down the axon, functional microtubules are required. Altered microtubule dynamics induced by changes in expression of microtubule-associated tau protein affects normal microtubule function and interferes with axonal transport. Here we investigate the effects of the nontaxoid-binding-site microtubule-stabilizing agents peloruside A (PelA) and Laulimalide, compared with the taxoid-site-binding agents paclitaxel (Ptx) and ixabepilone, on axonal transport of mitochondria in 1-day-old rat pup cerebral cortical neuron cultures. The differences in effects of these two types of compound on mitochondrial trafficking were specifically compared under conditions of excess tau expression. PelA and Laulimalide had no adverse effects on their own on mitochondrial transport compared with Ptx and ixabepilone, which inhibited mitochondrial run length at higher concentrations. PelA, like Ptx, was able to partially reverse the blocked mitochondrial transport seen in ECFP-htau40-overexpressing neurons, although at higher concentrations of microtubule-stabilizing agent, the PelA response was improved over the Ptx response. These results support a neuroprotective effect of microtubule stabilization in maintaining axonal transport in neurons overexpressing tau protein and may be beneficial in reducing the severity of neurodegenerative diseases such as Alzheimer's disease. © 2014 Wiley Periodicals, Inc.
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Structural basis of microtubule stabilization by Laulimalide and peloruside a.
Angewandte Chemie International Edition, 2014Co-Authors: Andrea E. Prota, Karl-heinz Altmann, Peter T. Northcote, John H. Miller, Katja Bargsten, May Marsh, José Fernando Díaz, Michel O. SteinmetzAbstract:Laulimalide and peloruside A are microtubule-stabilizing agents (MSAs), the mechanism of action on microtubules of which is poorly defined. Here, using X-ray crystallography it is shown that Laulimalide and peloruside A bind to a unique non-taxane site on β-tubulin and use their respective macrolide core structures to interact with a second tubulin dimer across protofilaments. At the same time, they allosterically stabilize the taxane-site M-loop that establishes lateral tubulin contacts in microtubules. Structures of ternary complexes of tubulin with Laulimalide/peloruside A and epothilone A are also solved, and a crosstalk between the Laulimalide/peloruside and taxane sites via the M-loop of β-tubulin is found. Together, the data define the mechanism of action of Laulimalide and peloruside A on tubulin and microtubules. The data further provide a structural framework for understanding the synergy observed between two classes of MSAs in tubulin assembly and the inhibition of cancer cell growth.
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Characterizing the Laulimalide–peloruside binding site using site-directed mutagenesis of TUB2 in S. cerevisiae
Mol. BioSyst., 2014Co-Authors: Reem Hanna, Peter T. Northcote, David S Bellows, Paul H Atkinson, David R. Maass, Paul H. Teesdale-spittle, John H. MillerAbstract:Baker's yeast, Saccharomyces cerevisiae, has significant sequence conservation with a core subset of mammalian proteins and can serve as a model for disease processes. The aim of this study was to determine whether yeast could be used as a model system to identify new agents that interact with the Laulimalide–peloruside binding site on β-tubulin. Agents that bind to this site cause stabilization of microtubules and interfere with cell division. Based on the location of the proposed Laulimalide–peloruside binding site and of previously identified mutations shown to cause resistance in mammalian cells, we made the corresponding mutations in yeast and tested whether they conferred resistance to Laulimalide and peloruside. Mutations A296T and R306H, which cause 6-fold and 40-fold increased resistance in human 1A9 ovarian carcinoma cells, respectively, also led to resistance in yeast to these compounds. Similarly, other mutations led to resistance or, in one case, increased sensitivity. Thus, we conclude that yeast is an appropriate model to screen for small molecule drugs that may be efficacious in cancer therapy in humans through the newly characterised Laulimalide–peloruside binding site.
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characterizing the Laulimalide peloruside binding site using site directed mutagenesis of tub2 in s cerevisiae
Molecular BioSystems, 2014Co-Authors: Reem Hanna, Peter T. Northcote, David S Bellows, Paul H Atkinson, David R. Maass, Paul H Teesdalespittle, John H. MillerAbstract:Baker's yeast, Saccharomyces cerevisiae, has significant sequence conservation with a core subset of mammalian proteins and can serve as a model for disease processes. The aim of this study was to determine whether yeast could be used as a model system to identify new agents that interact with the Laulimalide–peloruside binding site on β-tubulin. Agents that bind to this site cause stabilization of microtubules and interfere with cell division. Based on the location of the proposed Laulimalide–peloruside binding site and of previously identified mutations shown to cause resistance in mammalian cells, we made the corresponding mutations in yeast and tested whether they conferred resistance to Laulimalide and peloruside. Mutations A296T and R306H, which cause 6-fold and 40-fold increased resistance in human 1A9 ovarian carcinoma cells, respectively, also led to resistance in yeast to these compounds. Similarly, other mutations led to resistance or, in one case, increased sensitivity. Thus, we conclude that yeast is an appropriate model to screen for small molecule drugs that may be efficacious in cancer therapy in humans through the newly characterised Laulimalide–peloruside binding site.
Arun K. Ghosh - One of the best experts on this subject based on the ideXlab platform.
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the assembly inducing Laulimalide peloruside a binding site on tubulin molecular modeling and biochemical studies with 3h peloruside a
Journal of Chemical Information and Modeling, 2010Co-Authors: Tam Luong Nguyen, Arun K. Ghosh, Rick Gussio, Ernest HamelAbstract:We used synthetic peloruside A for the commercial preparation of [3H]peloruside A. The radiolabeled compound bound to preformed tubulin polymer in amounts stoichiometric with the polymer’s tubulin content, with an apparent Kd value of 0.35 μM. A less active peloruside A analogue, (11-R)-peloruside A and Laulimalide acted as competitive inhibitors of the binding of the [3H]peloruside A, with apparent Ki values of 9.3 and 0.25 μM, respectively. Paclitaxel, epothilone B, and discodermolide had essentially no ability to inhibit [3H]peloruside A binding, confirming that these compounds bind to a different site on tubulin polymer. We modeled both Laulimalide and peloruside A into the binding site on β-tubulin that was identified by Huzil et al. (J. Mol. Biol. 2008, 378, 1016−1030), but our model provides a more reasonable structural basis for the protein−ligand interaction. There is a more complete desolvation of the peloruside A ligand and a greater array of favorable hydrophobic and electrostatic interactions...
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The Assembly-Inducing Laulimalide/Peloruside A Binding Site on Tubulin: Molecular Modeling and Biochemical Studies with [3H]Peloruside A
Journal of Chemical Information and Modeling, 2010Co-Authors: Tam Luong Nguyen, Arun K. Ghosh, Rick Gussio, Ernest HamelAbstract:We used synthetic peloruside A for the commercial preparation of [3H]peloruside A. The radiolabeled compound bound to preformed tubulin polymer in amounts stoichiometric with the polymer’s tubulin content, with an apparent Kd value of 0.35 μM. A less active peloruside A analogue, (11-R)-peloruside A and Laulimalide acted as competitive inhibitors of the binding of the [3H]peloruside A, with apparent Ki values of 9.3 and 0.25 μM, respectively. Paclitaxel, epothilone B, and discodermolide had essentially no ability to inhibit [3H]peloruside A binding, confirming that these compounds bind to a different site on tubulin polymer. We modeled both Laulimalide and peloruside A into the binding site on β-tubulin that was identified by Huzil et al. (J. Mol. Biol. 2008, 378, 1016−1030), but our model provides a more reasonable structural basis for the protein−ligand interaction. There is a more complete desolvation of the peloruside A ligand and a greater array of favorable hydrophobic and electrostatic interactions...
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Synergistic effects of peloruside A and Laulimalide with taxoid site drugs, but not with each other, on tubulin assembly.
Molecular Pharmacology, 2006Co-Authors: Ernest Hamel, Arun K. Ghosh, M. Katherine Jung, Peter T. Northcote, John H. Miller, Billy W. Day, Dennis P. Curran, Mark Cushman, K. C. Nicolaou, Ian PatersonAbstract:Previous studies on the drug content of pelleted tubulin polymers suggest that peloruside A binds in the Laulimalide site, which is distinct from the taxoid site. In a tubulin assembly system containing microtubule-associated proteins and GTP, however, peloruside A was significantly less active than Laulimalide, inducing assembly in a manner that was most similar to sarcodictyins A and B. Because peloruside A thus far seems to be the only compound that mimics the action of Laulimalide, we examined combinations of microtubule-stabilizing agents for synergistic effects on tubulin assembly. We found that peloruside A and Laulimalide showed no synergism but that both compounds could act synergistically with a number of taxoid site agents [paclitaxel, epothilones A/B, discodermolide, dictyostatin, eleutherobin, the steroid derivative 17β-acetoxy-2-ethoxy-6-oxo-B-homo-estra-1,3,5(10)-trien-3-ol, and cyclostreptin]. None of the taxoid site compounds showed any synergism with each other. From an initial study with peloruside A and cyclostreptin, we conclude that the synergism phenomenon derives, at least in part, from an apparent lowering of the tubulin critical concentration with drug combinations compared with single drugs. The apparent binding of peloruside A in the Laulimalide site led us to attempt construction of a pharmacophore model based on superposition of an energy-minimized structure of peloruside A on the crystal structure of Laulimalide. Although the different sizes of the macrocycles limited our ability to superimpose the two molecules, atom correspondences that were observed were consistent with the difficulty so far experienced in creation of fully active analogs of Laulimalide.
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Conformations of Laulimalide in DMSO-d6
Journal of the American Chemical Society, 2005Co-Authors: Pahk Thepchatri, Arun K. Ghosh, Daniel O. Cicero, Edith Monteagudo, Ben Cornett, Eric R. Weeks, James P. SnyderAbstract:Laulimalide is one of the newest naturally occurring macrolides known to act as a microtubule stabilizing agent with properties similar to Taxol. It also stands as being one of the most flexible with 18 rotatable bonds. This large number of rotatable bonds allows for approximately 318 potential conformers. To examine the conformational energy surface of Laulimalide, we have performed an NAMFIS deconvolution analysis for Laulimalide in DMSO-d6. The latter has been supplemented with a post-NAMFIS energy analysis at the Becke3LYP/6-31G* level that examines the opposing effects of internal hydrogen bonding and syn-pentane interactions. In this way, we have identified 15 Laulimalide conformations that can be classified into 5 different families: Supine, Convex, Cobra, Stretch, and Concave motifs.
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Laulimalide and Paclitaxel: A Comparison of Their Effects on Tubulin Assembly and Their Synergistic Action When Present Simultaneously
Molecular Pharmacology, 2004Co-Authors: Eric J. Gapud, Arun K. Ghosh, Ruoli Bai, Ernest HamelAbstract:Previous work has shown that Laulimalide, a sponge-derived natural product, resembles paclitaxel in enhancing tubulin assembly and in its effects on cellular microtubules. The two compounds, however, seem to have distinct binding sites on tubulin polymer. Nearly equimolar amounts of tubulin, Laulimalide, and paclitaxel are recovered from microtubules formed with both drugs. In the present study, we searched for differences between Laulimalide and paclitaxel in their interactions with tubulin polymer. Laulimalide was compared with paclitaxel and epothilone A, a natural product that competes with paclitaxel in binding to microtubules, for assembly properties at different temperatures and for effects of GTP and microtubule-associated proteins on assembly. Although minor differences were observed among the three drugs, their overall effects were highly similar, except that aberrant assembly products were observed more frequently with paclitaxel and that the polymers formed with Laulimalide and epothilone A were more stable at 0 degrees C. The most dramatic difference observed between Laulimalide and epothilone A was that only Laulimalide was able to enhance assembly synergistically with paclitaxel, as would be predicted if the two drugs bound at different sites in polymer. Because stoichiometric amounts of Laulimalide and paclitaxel can cause extensive tubulin assembly, maximum synergy was observed at lower temperatures under reaction conditions in which each drug alone is relatively inactive. Laulimalide-induced assembly, like paclitaxel-induced assembly, was inhibited by drugs that inhibit tubulin assembly by binding at either the colchicine- or vinblastine-binding site. When radiolabeled GTP is present in a reaction mixture with either Laulimalide or paclitaxel, nucleotide hydrolysis occurs with incorporation of radiolabeled GDP into polymer.
Johann Mulzer - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and biological evaluation of a des-dihydropyran Laulimalide analog
Tetrahedron Letters, 2009Co-Authors: Andreas Gollner, Karl-heinz Altmann, Jürg Gertsch, Johann MulzerAbstract:Abstract The preparation of a novel simplified Laulimalide analog via a highly convergent and efficient route and its biological evaluation are presented. The outlined route enables the synthesis of C 5 –C 9 modified analog 2 and uses Julia–Kocienski olefination for fragment assembly and a regioselective Yamaguchi macrolactonization for ring closure. This strategy should be suitable for the generation of various new C 5 –C 9 des -dihydropyran Laulimalide derivatives for further SAR studies.
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The Laulimalide Family: Total Synthesis and Biological Evaluation of NeoLaulimalide, IsoLaulimalide, Laulimalide and a Nonnatural Analogue
Chemistry - A European Journal, 2009Co-Authors: Andreas Gollner, Karl-heinz Altmann, Jürg Gertsch, Johann MulzerAbstract:We herein describe in full detail the first total synthesis of the antitumor agents neoLaulimalide and isoLaulimalide as well as a highly efficient route to Laulimalide. A Kulinkovich reaction followed by a cyclopropyl-allyl rearrangement is used to install the exo-methylene group. The C(2)-C(16) aldehyde fragment is coupled with the C(17)-C(28) sulfone fragments by a highly (E)-selective Julia-Lythgoe-Kocienski olefination to deliver the key intermediates of all three syntheses. Various conditions for the Yamaguchi macrolactonization are applied to close the individual macrocycles. Finally a carefully elaborated endgame was developed to solve the problem of acyl migration in the case of neoLaulimalide. All compounds were tested against several cell lines. The cytotoxicity of neoLaulimalide could be confirmed for the first time since its original isolation and it could be shown that it induces tubulin polymerization as efficiently as Laulimalide.
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Total Synthesis of the Microtubule Stabilizing Antitumor Agent Laulimalide and Some Nonnatural Analogues: The Power of Sharpless' Asymmetric Epoxidation
The Journal of Organic Chemistry, 2003Co-Authors: Anjum Ahmed, E. Kate Hoegenauer, Valentin S. Enev, Martin Hanbauer, Hanspeter Kaehlig, Elisabeth Öhler, Johann MulzerAbstract:Three different routes are described for the synthesis of deoxyLaulimalide (3), which is the immediate precursor of the marine sponge metabolite Laulimalide (1). These routes mainly differ with respect to their ring closing step. Thus, route 1 uses a Still-Gennari olefination, route 2 a Yamaguchi lactonization, and route 3 an intramolecular allylsilane-aldehyde addition for establishing the macrocyclic structure. The unprotected deoxy derivative 3 was subjected to Sharpless' asymmetric epoxidation (SAE). With (R,R)-tartrate the 16,17-epoxide Laulimalide (1) is formed selectively, whereas (S,S)-tartrate generates the 21,22-epoxide 142. This demonstrates the high reagent control involved in the SAE process, which in this case is used to achieve high stereo- and regioselectivity. Laulimalide and some derivatives thereof have been tested with respect to antitumor activity and compared to standard compounds paclitaxel and epothilone B.
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total synthesis of the antitumor agent Laulimalide
Tetrahedron Letters, 2002Co-Authors: Johann Mulzer, Martin HanbauerAbstract:A stereocontrolled synthesis of the title compound is described. Key steps are an allylsilane addition to a chiral acetal as the major coupling step and a Yamaguchi macrolactonization for ring closure.
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A chirally catalysed ene reaction in a novel formal total synthesis of the antitumor agent Laulimalide
Tetrahedron Letters, 2002Co-Authors: Michael R Pitts, Johann MulzerAbstract:Abstract A short highly efficient synthesis of the C3 C16 fragment 2 of Laulimalide 1 is described. Fragment 2 was a key intermediate in a previous approach and thus constitutes a formal total synthesis with improved efficiency. The key steps are an Evans’ alkylation, a Brown allylation and a chirally catalysed stereocontrolled ene-reaction.
Peter T. Northcote - One of the best experts on this subject based on the ideXlab platform.
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Preclinical Development Peloruside- and Laulimalide-Resistant Human Ovarian Carcinoma Cells Have bI-Tubulin Mutations and Altered Expression of bII- and bIII-Tubulin Isotypes
2016Co-Authors: Anja Wilmes, Ernest Hamel, Pisana Rawson, Bronwyn M. Kivell, Peter T. Northcote, Janet Crawford, Paraskevi Giannakakou, John H. MillerAbstract:Peloruside A and Laulimalide are potent microtubule-stabilizing natural products with a mechanism of action similar to that of paclitaxel. However, the binding site of peloruside A and Laulimalide on tubulin remains poorly understood. Drug resistance in anticancer treatment is a serious problem. We developed peloruside A- and Laulimalide-resistant cell lines by selecting 1A9 human ovarian carcinoma cells that were able to grow in the presence of one of these agents. The 1A9-Laulimalide resistant cells (L4) were 39-fold resistant to the selecting agent and 39-fold cross-resistant to peloruside A, whereas the 1A9-peloruside A resistant cells (R1) were 6-fold resistant to the selecting agent while they remained sensitive to Laulimalide. Neither cell line showed resistance to paclitaxel or other drugs that bind to the taxoid site on b-tubulin nor was there resistance to microtubule-destabilizing drugs. The resistant cells exhibited impaired peloruside A/ Laulimalide-induced tubulin polymerization and impaired mitotic arrest. Tubulin mutations were found in the bI-tubulin isotype, R306H or R306C for L4 and A296T for R1 cells. This is the first cell-based evidence to support a b-tubulin–binding site for peloruside A and Laulimalide. To determine whether the different resistance phenotypes of the cells were attributable to any other tubulin alterations, the b-tubulin isotype composition of the cells was examined. Increased expression of bII- and bIII-tubulin was observed in L4 cells only. These results provide insight into how alterations in tubulin lead to unique resistance profiles for two drugs, peloruside A and Laulimalide, that have a similar mode of action. Mol Cancer Ther; 10(8); 1–11. 2011 AACR
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Structural basis of microtubule stabilization by Laulimalide and peloruside a.
Angewandte Chemie International Edition, 2014Co-Authors: Andrea E. Prota, Karl-heinz Altmann, Peter T. Northcote, John H. Miller, Katja Bargsten, May Marsh, José Fernando Díaz, Michel O. SteinmetzAbstract:Laulimalide and peloruside A are microtubule-stabilizing agents (MSAs), the mechanism of action on microtubules of which is poorly defined. Here, using X-ray crystallography it is shown that Laulimalide and peloruside A bind to a unique non-taxane site on β-tubulin and use their respective macrolide core structures to interact with a second tubulin dimer across protofilaments. At the same time, they allosterically stabilize the taxane-site M-loop that establishes lateral tubulin contacts in microtubules. Structures of ternary complexes of tubulin with Laulimalide/peloruside A and epothilone A are also solved, and a crosstalk between the Laulimalide/peloruside and taxane sites via the M-loop of β-tubulin is found. Together, the data define the mechanism of action of Laulimalide and peloruside A on tubulin and microtubules. The data further provide a structural framework for understanding the synergy observed between two classes of MSAs in tubulin assembly and the inhibition of cancer cell growth.
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Characterizing the Laulimalide–peloruside binding site using site-directed mutagenesis of TUB2 in S. cerevisiae
Mol. BioSyst., 2014Co-Authors: Reem Hanna, Peter T. Northcote, David S Bellows, Paul H Atkinson, David R. Maass, Paul H. Teesdale-spittle, John H. MillerAbstract:Baker's yeast, Saccharomyces cerevisiae, has significant sequence conservation with a core subset of mammalian proteins and can serve as a model for disease processes. The aim of this study was to determine whether yeast could be used as a model system to identify new agents that interact with the Laulimalide–peloruside binding site on β-tubulin. Agents that bind to this site cause stabilization of microtubules and interfere with cell division. Based on the location of the proposed Laulimalide–peloruside binding site and of previously identified mutations shown to cause resistance in mammalian cells, we made the corresponding mutations in yeast and tested whether they conferred resistance to Laulimalide and peloruside. Mutations A296T and R306H, which cause 6-fold and 40-fold increased resistance in human 1A9 ovarian carcinoma cells, respectively, also led to resistance in yeast to these compounds. Similarly, other mutations led to resistance or, in one case, increased sensitivity. Thus, we conclude that yeast is an appropriate model to screen for small molecule drugs that may be efficacious in cancer therapy in humans through the newly characterised Laulimalide–peloruside binding site.
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characterizing the Laulimalide peloruside binding site using site directed mutagenesis of tub2 in s cerevisiae
Molecular BioSystems, 2014Co-Authors: Reem Hanna, Peter T. Northcote, David S Bellows, Paul H Atkinson, David R. Maass, Paul H Teesdalespittle, John H. MillerAbstract:Baker's yeast, Saccharomyces cerevisiae, has significant sequence conservation with a core subset of mammalian proteins and can serve as a model for disease processes. The aim of this study was to determine whether yeast could be used as a model system to identify new agents that interact with the Laulimalide–peloruside binding site on β-tubulin. Agents that bind to this site cause stabilization of microtubules and interfere with cell division. Based on the location of the proposed Laulimalide–peloruside binding site and of previously identified mutations shown to cause resistance in mammalian cells, we made the corresponding mutations in yeast and tested whether they conferred resistance to Laulimalide and peloruside. Mutations A296T and R306H, which cause 6-fold and 40-fold increased resistance in human 1A9 ovarian carcinoma cells, respectively, also led to resistance in yeast to these compounds. Similarly, other mutations led to resistance or, in one case, increased sensitivity. Thus, we conclude that yeast is an appropriate model to screen for small molecule drugs that may be efficacious in cancer therapy in humans through the newly characterised Laulimalide–peloruside binding site.
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Acquired Resistance to Peloruside A and Laulimalide is Associated with Downregulation of Vimentin in Human Ovarian Carcinoma Cells
Pharmaceutical Research, 2012Co-Authors: Arun Kanakkanthara, Pisana Rawson, Peter T. Northcote, John H. MillerAbstract:Purpose Acquired β-tubulin alterations in human ovarian carcinoma 1A9 cells were previously shown to confer resistance to the microtubule stabilizing agents peloruside A (PLA) and Laulimalide (LAU). We examined the proteome of resistant cells to see what other protein changes occurred as a result of the acquired drug resistance.
Ian Paterson - One of the best experts on this subject based on the ideXlab platform.
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Synergistic interactions between peloruside A and other microtubule-stabilizing and destabilizing agents in cultured human ovarian carcinoma cells and murine T cells
Cancer Chemotherapy and Pharmacology, 2011Co-Authors: Anja Wilmes, Ariane Chan, Peter T. Northcote, Ian Paterson, David O’sullivan, Clarissa Chandrahasen, Anne Camille La Flamme, John H. MillerAbstract:Purpose Microtubule-stabilizing agents are an important class of anticancer compounds. Peloruside A and Laulimalide bind to a different site on the microtubule to taxoid site drugs such as paclitaxel (Taxol^®), docetaxel (Taxotere^®), ixabepilone (Ixempra^®), the epothilones, and discodermolide. The purpose of this study was to examine the synergistic interactions of these drugs when given in combination in relation to the differences in their binding sites on the microtubule. Methods Human ovarian carcinoma cells (1A9 cells) and murine T cells were treated with different combinations of microtubule-stabilizing or destabilizing agents. The compounds were given individually and in combination, and the antiproliferative activity was assessed to calculate a combination index (CI) from the equation: CI = D _1/ Dx _1 + D _2/ Dx _2 in which D _1 and D _2 are the concentrations of drug 1 and drug 2 that when given together give the same response as drug 1 and 2 alone ( Dx _1 and Dx _2). Thus, a CI value of less than 1.0 indicates a synergistic effect between the two drugs in which the response to the two drugs given together is greater than the additive response of the two drugs if given on their own. Results As anticipated from previous in vitro studies, peloruside A and Laulimalide did not synergize with each other. They also failed to synergize with the microtubule-destabilizing agents vinblastine and 2-methoxyestradiol. Peloruside A and Laulimalide did, however, synergize with the epothilones, as had been previously shown, but not with docetaxel or discodermolide. Conclusions Combining two microtubule-targeting agents with different binding sites does not guarantee a synergistic interaction in cells, and additional factors are likely to be involved. This study highlights the importance of preclinical testing of actual combinations of drugs before proceeding into clinical trials.
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Synergistic interactions between peloruside A and other microtubule-stabilizing and destabilizing agents in cultured human ovarian carcinoma cells and murine T cells.
Cancer Chemotherapy and Pharmacology, 2010Co-Authors: Anja Wilmes, Ariane Chan, Peter T. Northcote, Ian Paterson, Clarissa Chandrahasen, Anne Camille La Flamme, David O'sullivan, John H. MillerAbstract:Purpose Microtubule-stabilizing agents are an important class of anticancer compounds. Peloruside A and Laulimalide bind to a different site on the microtubule to taxoid site drugs such as paclitaxel (Taxol®), docetaxel (Taxotere®), ixabepilone (Ixempra®), the epothilones, and discodermolide. The purpose of this study was to examine the synergistic interactions of these drugs when given in combination in relation to the differences in their binding sites on the microtubule.
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Synergistic effects of peloruside A and Laulimalide with taxoid site drugs, but not with each other, on tubulin assembly.
Molecular Pharmacology, 2006Co-Authors: Ernest Hamel, Arun K. Ghosh, M. Katherine Jung, Peter T. Northcote, John H. Miller, Billy W. Day, Dennis P. Curran, Mark Cushman, K. C. Nicolaou, Ian PatersonAbstract:Previous studies on the drug content of pelleted tubulin polymers suggest that peloruside A binds in the Laulimalide site, which is distinct from the taxoid site. In a tubulin assembly system containing microtubule-associated proteins and GTP, however, peloruside A was significantly less active than Laulimalide, inducing assembly in a manner that was most similar to sarcodictyins A and B. Because peloruside A thus far seems to be the only compound that mimics the action of Laulimalide, we examined combinations of microtubule-stabilizing agents for synergistic effects on tubulin assembly. We found that peloruside A and Laulimalide showed no synergism but that both compounds could act synergistically with a number of taxoid site agents [paclitaxel, epothilones A/B, discodermolide, dictyostatin, eleutherobin, the steroid derivative 17β-acetoxy-2-ethoxy-6-oxo-B-homo-estra-1,3,5(10)-trien-3-ol, and cyclostreptin]. None of the taxoid site compounds showed any synergism with each other. From an initial study with peloruside A and cyclostreptin, we conclude that the synergism phenomenon derives, at least in part, from an apparent lowering of the tubulin critical concentration with drug combinations compared with single drugs. The apparent binding of peloruside A in the Laulimalide site led us to attempt construction of a pharmacophore model based on superposition of an energy-minimized structure of peloruside A on the crystal structure of Laulimalide. Although the different sizes of the macrocycles limited our ability to superimpose the two molecules, atom correspondences that were observed were consistent with the difficulty so far experienced in creation of fully active analogs of Laulimalide.
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Conformational studies and solution structure of Laulimalide and simplified analogues using NMR spectroscopy and molecular modelling
Tetrahedron Letters, 2005Co-Authors: Ian Paterson, Dirk Menche, Robert A. Britton, Anders E. Håkansson, Marı́a Á. Silva-martı́nezAbstract:The solution structures of the potent microtubule-stabilizing anti-cancer agent Laulimalide and simplified analogues were determined by a combination of high field 1H NMR spectroscopic studies (J-based configuration analysis and NOESY) and constrained molecular dynamics simulations and discussed in relation to their antiproliferative activity.
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Design, synthesis and biological evaluation of novel, simplified analogues of Laulimalide: modification of the side chain.
Bioorganic & Medicinal Chemistry Letters, 2005Co-Authors: Ian Paterson, Rubén M. Buey, Dirk Menche, Anders E. Håkansson, Adrian Longstaff, David T. Wong, Isabel Barasoain, J. Fernando DíazAbstract:Novel, simplified analogues of the microtubule-stabilizing anticancer agent Laulimalide, including the first derivatives with unnatural side chains, were designed by molecular modelling, synthesized by a late-stage diversification strategy, and evaluated in vitro for growth inhibition of human ovarian carcinoma cell lines (A2780, A2780/AD10).