1. Introduction

Marine Drugs

1660-3397

Molecular Diversity Preservation International

10.3390/md8041059

marinedrugs-08-01059

Review

Microtubule-Stabilizing Drugs from Marine Sponges: Focus on Peloruside A and Zampanolide

Miller

John H.

1* Singh

A. Jonathan

2 Northcote

Peter T.

1 School of Biological Sciences and Centre for Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington, New Zealand 2 School of Chemical and Physical Sciences and Centre for Biodiscovery, Victoria University of Wellington, PO Box 600, Wellington, New Zealand; E-Mails: jonathan.singh@vuw.ac.nz (A.J.S.); peter.northcote@vuw.ac.nz (P.T.N.)

*Author to whom correspondence should be addressed; E-Mail: john.h.miller@vuw.ac.nz; Tel.: +64-4-463-6082; Fax: +64-4-463-5331.

2010

31 3 2010

8 4 1059 1079 1 3 2010 13 3 2010 29 3 2010

2010

This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).

Marine sponges are an excellent source of bioactive secondary metabolites with potential therapeutic value in the treatment of diseases. One group of compounds of particular interest is the microtubule-stabilizing agents, the most well-known compound of this group being paclitaxel (Taxol^®), an anti-cancer compound isolated from the bark and leaves of the Pacific yew tree. This review focuses on two of the more recent additions to this important class of drugs, peloruside A and zampanolide, both isolated from marine sponges. Peloruside A was isolated from Mycale hentscheli collected in New Zealand coastal waters, and it already shows promising anti-cancer activity. Two other potent bioactive compounds with different modes of action but isolated from the same sponge, mycalamide A and pateamine, will also be discussed. The fourth compound, zampanolide, most recently isolated from the Tongan sponge Cacospongia mycofijiensis, has only recently been added to the microtubule-stabilizing group of compounds, and further work is in progress to determine its activity profile relative to peloruside A and other drugs of this class.

mycalamide pateamine peloruside zampanolide microtubule stabilization

1. Introduction 1.1. Drugs from marine sources

Despite significant medical advances, cancer continues to be a major cause of disease-related death in most countries. New therapeutic options to treat this disease are a high priority for many pharmaceutical companies and independent research organisations. Current drug discovery involves screening for potential lead compounds with known targets, few side effects, and activity against one or more diseases. There is then potential to remodel the lead compound to improve activity and expand its therapeutic window. De novo design and synthesis of bioactive molecules, even with sophisticated computer modelling, is unlikely to replace the millions of years of evolution and natural selection available to living organisms, and thus, natural products, particularly those from marine sources, are still the most promising approach to new drug discovery [1–7]. The diversity of marine life can be attributed to the fact that oceans cover most of the earth’s surface, and marine organisms pre-date terrestrial organisms by hundreds of millions of years, allowing for greater evolutionary variation [8,9]. The success of marine-derived drugs in the clinical treatment of cancer has been particularly encouraging [10–12]. Of the many different types of marine organisms used as a source for drug discovery, sponges have proven to be one of the most successful groups [13], followed by others such as marine bacteria, coelenterates, tunicates, and bryozoans. Marine-derived drugs are generally more potent than plant-derived compounds because of the dilution effect of the ocean environment. Determining the actual source of the bioactive secondary metabolites is an interesting problem; however, the chemical structures of the metabolites provide clues to the metabolic pathways involved in their biosynthesis. Marine sponges harbour microorganisms on their surfaces, in their canal systems, and in their intercellular spaces, and these may contribute up to 40% of the total cellular content of a sponge. Most of these microorganisms are endosymbionts and are probably the major source of the compounds isolated from marine sponges [14–18]. Some indirect evidence for this is the fact that a species of sponge that produces a compound often shows considerable variability between individuals and locations, ranging from some that produce no compound to others that produce large amounts of the compound [19,20].

1.2. Cytoskeletal targets

The actual targets of a number of the compounds isolated from marine organisms, including some of those in clinical use, are unidentified, and further work on these compounds is required to understand their mode of action. A common target of bioactive compounds in eukaryotes, however, is the cytoskeleton, largely because it has a major role in many essential cell processes including cell division, cell movement, and cell secretion. The cytoskeleton consists primarily of microtubules, microfilaments, and intermediate filaments. Microtubules and microfilaments are the most vulnerable, and many bioactive compounds target these two structures [21–26]. Microfilaments consist of G-actin monomer proteins polymerized into long, thin F-actin filaments. Examples of marine-derived drugs that target the actin cytoskeleton and cause depolymerization of the filaments are latrunculin A, halichondramide, mycalolide, and the swinholides. Marine drugs that induce or support actin polymerization include phalloidin, jasplakinolide, and dolastatin. The other main cytoskeletal target, the microtubule, consists of polymers of α- and β-tubulin dimers, and there are drugs that either promote tubulin polymerization (microtubule-stabilizing agents) (MSAs) or promote depolymerization (microtubule-destabilizing agents) (MDAs). Paclitaxel was the first MSA discovered and translated into the clinic as an anti-cancer drug, being approved by the U.S. FDA for treatment of ovarian cancer in 1992 [27]. More recent work with paclitaxel involves alterations in its formulation and delivery in attempts to maximise its effectiveness and decrease its toxicity [28]. There are a number of excellent reviews on drugs that target the microtubules and microfilaments in eukaryote cells [21–26,29].

1.3. Microtubule-targeting drugs

The number of marine drugs that have been identified as microtubule targeting agents (MTAs) has increased considerably over the years. The first drugs identified as MTAs such as colchicine and the Vinca alkaloids, both derived from plants, were found to depolymerize microtubules [23]. Other MTAs have been isolated from non-marine organisms, such as paclitaxel, isolated from the Pacific yew tree Taxus brevifolia [30,31], and its semi-synthetic derivative docetaxel, the steroid MDA taccalonolide isolated from the plant Tacca chantrieri [32], and the MSAs epothilone A and B, isolated from myxobacteria [33]. Other MSAs are derived from marine sources but not from sponges, including eleutherobin [34,35] and sarcodictyin [36,37], both from soft corals. Marine sponges, however, remain the most prolific source of MTAs [24–26] and include the MDAs jaspolide, dolastatin, halichondrin, spongistatin, and milnamide and the MSAs hemiasterlin, dictyostatin, discodermolide, laulimalide, peloruside A, and zampanolide. The present review will focus on the last two of the MDAs listed above, peloruside A (1) and zampanolide (2) (Figure 1). The history of their isolation, purification, and the determination of their mode of action will be discussed. In addition, two other bioactive compounds collected from the same sponge that produces peloruside A but that does not target the cytoskeleton, the mycalamides 3–5 and pateamine (6), will also be discussed in conjunction with peloruside A.

2. Discussion 2.1. Peloruside A and its cell-mates, mycalamide A and pateamine

The history of lead compound development from marine natural sources is a fascinating aspect of drug discovery. Dr Peter Northcote, working with Dr John Blunt and Dr Murray Munro at the University of Canterbury in Christchurch, and then later in his own laboratory at Victoria University of Wellington, was instrumental in the identification of two of three bioactive secondary metabolites isolated from a single species of marine sponge Mycale hentscheli from New Zealand coastal waters (Figure 2). The sponge produces three structurally dissimilar classes of secondary metabolites with potent bioactivity in the low nanomolar range, the mycalamides 3–5, pateamine (6), and the pelorusides A (1) and B (7) [38–40] (Figure 1).

2.2. Mycalamides

Mycalamide A (3) was originally isolated from Mycale sp. marine sponges collected in Otago Harbour in New Zealand by Perry et al. in 1988 using a bioactivity-directed isolation protocol [41]. Mycalamide analogues B (4) and D (5) have also been identified in Mycale marine sponges [42,43]. A related compound, mycalamide C, was reported from a Stylinos sp. sponge [44]. The mycalamides have a high degree of structural similarity to pederin, a toxin isolated from the terrestrial blister beetle Paederus fiscipes [45–47], as well as the onnamides and theopederins, isolated from Theonella and Discodermia marine sponges [48–54]. The structures of mycalamides A, B, and D, 3–5, are shown in Figure 1. Mycalamide A was found to be a potent inhibitor of cell proliferation (IC₅₀ 1–5 nM) [38,42,55] and, like onnamide A, inhibits in vitro protein translation at concentrations close to those required to inhibit cell proliferation [55]. Mycalamide B (4), with three oxymethyl groups instead of two, is a more potent inhibitor of both cell proliferation and in vitro translation than mycalamide A, suggesting that an additional oxymethyl group increases the affinity of binding to the cellular target, rather than promotes uptake by the cell. Another mycalamide congener isolated from the same sponge species, mycalamide D (5), with one oxymethyl group, is less potent than mycalamides A or B [43], and this decrease in activity may result from the increased polarity of the analog and therefore decreased entry into the cell. The ability of pederin, with structural similarities to the mycalamides, to inhibit protein synthesis by binding irreversibly to ribosomes was originally described by Carrasco et al. in 1976 [56]. Closer examination of the structure of pederin revealed a region in the molecule similar to a peptide bond, and this may explain the protein synthesis inhibitor properties of pederin [57]. Both pederin and mycalamide bind to the large ribosomal subunit of eukaryotic cells [58].

The total synthesis of mycalamide A has been described [59–63], as well as syntheses of a number of biologically active analogs and semi-synthetic derivatives [57,64–68]. The synthetic analogue 18-O-methyl mycalamide B is slightly more potent than mycalamide A and inhibits [¹²⁵I]-uridine and [³H]-leucine incorporation into RNA and protein in cultured cells [57]. In animal studies, mycalamides A and B increased the life span of mice bearing ascitic P388 lymphoma and other solid tumours, although significant side effects were observed [55]. Since this initial study, further in vivo studies with the mycalamides have not been reported in the literature.

2.3. Pateamine

Pateamine (6) (Figure 1) was reported from sponges collected in Fiordland, New Zealand by Northcote et al. in 1991 and found to be highly toxic against P388 leukemic cells (IC₅₀ = 0.15 ng/mL), as well as exhibiting anti-fungal properties [69]. Romo et al. described the first synthesis of pateamine in 1998 and also noted its immunosuppressive properties [70]. Pateamine was proposed to be a protein synthesis inhibitor, based on the early work with the compound. In one study, pateamine was chemically modified by the addition of dexamethasone to the primary C-3 amino group to allow yeast-three hybrid screens to be performed to identify the cellular receptor of the drug [70,71]. To our knowledge, however, no further work using this approach has been published. The cellular target of pateamine was subsequently identified by affinity chromatography to be the protein initiation factor eIF4A [72–74]. By stimulating eIF4A, pateamine inhibits protein synthesis. Interestingly, it was also shown to inhibit nonsense-mediated mRNA decay [75]. This second effect was also via eIF4A, but the mRNA decay was independent of the translation inhibition effects of the drug. Thus, pateamine is a novel small molecule inhibitor of protein synthesis that works by binding to and stimulating a eukaryote translation initiation factor. As such, it is an important molecular tool for studying the biochemical events of protein synthesis initiation and mRNA turnover.

2.4. Peloruside A 2.4.1. Discovery and mode of action

The third secondary metabolite from Mycale hentscheli that showed potent bioactivity was isolated in 1999 from sponges collected from Pelorus Sound on the north coast of the South Island of New Zealand [76]. This novel compound was named peloruside A (1) after the location where the sponges were found (Figure 1). Dr Northcote and his PhD student at the time, Lyndon West, identified peloruside A using a unique fractionation procedure that enriched for bioactive compounds on the basis of their intermediate solubility in aqueous methanol, being neither too lipophilic nor too hydrophilic. Peloruside A was initially found to be ten-fold less potent an inhibitor of proliferation of P388 murine leukemic cells (IC₅₀ = 18 nM) [76] than the two other natural products isolated from the same sponge, mycalamide A and pateamine. Although all three metabolites are cytotoxic at nanomolar concentrations, the mechanism of action of peloruside A differed considerably from the other two which were known protein synthesis inhibitors. Shortly after the structure of peloruside A was determined and published [76], Dr Northcote and Dr John Miller, a cell biologist at the same university, began collaborating together to identify new natural products and determine their modes of action. Although initial studies on the mechanism of action of peloruside A followed up on a false lead that was based on structural similarity of the active sites on peloruside A to those of bryostatin-1 [39], Kylie Hood, then a PhD student of Dr Miller’s, discovered that peloruside A had potent anti-mitotic activity, blocking cells in G₂/M of the cell cycle [39,40]. Further investigations determined that peloruside A stabilized the polymerized form of tubulin (Figure 3) and induced microtubule bundling in interphase cells and multiple asters in mitotic cells [77] in a similar manner to paclitaxel [31], an important anti-cancer drug used for the treatment of solid tumours of the breast, ovary, lung, head and neck [27,78]. The history of the discovery and development of paclitaxel as an anti-cancer agent has been summarised by Prof. Susan Band Horwitz in a special article to commemorate her impact in the field, published in the Journal of Natural Products [79].

In quantifying the activity of different MSA’s, the critical concentration (C_crit) is a useful comparative parameter. C_crit is the minimum concentration of tubulin that is required for polymerization to occur. GDP-tubulin in the absence of an MSA does not polymerize at all in vitro (C_crit > 200 μM) [80]. The C_crit for tubulin in the presence of peloruside A in a MAP-free in vitro system is higher than for tubulin in the presence of paclitaxel (11 μM versus 4 μM, respectively), indicating that it is a less potent MSA than paclitaxel [81]. Nevertheless peloruside A is capable of polymerizing microtubules in the absence of MAPs. Both the presence of GTP and MAPs can influence the C_crit for tubulin. For example, in the presence of paclitaxel, the C_crit for tubulin with MAPs and GTP present, MAPs only, GTP only, and in the absence of both MAPs and GTP is 0.2, 2, 4, and 22 μM, respectively [82]. The C_crit for tubulin after addition of peloruside A was only tested in the absence of MAPs and in the presence of GTP [81].

Recent studies in Dr Miller’s laboratory have also demonstrated that, like other MSA’s [83–86], peloruside A inhibits microtubule dynamics at concentrations near those needed to block progression through the cell cycle, but much lower than those needed to cause tubulin assembly in vitro [87]. Although not tested in mitotic cells, peloruside A significantly reduced the growth and shortening of microtubules in interphase cells, reducing the overall dynamicity of the microtubules.

2.4.2. Peloruside A effects on cell proteins

A proteomics study on human HL-60 promyelocytic leukemic cells used two-dimensional electrophoresis and differential in-gel electrophoresis (DIGE) to examine the protein changes in the cell following treatment with peloruside A [88]. An analysis of the affected proteins showed 17 proteins changed by 2-fold or more, and the changes were consistent with the known action of peloruside A on microtubules, as well as effects on proteins involved in apoptosis and stress. Others have also shown that blocking cells in mitotsis with anti-mitotic drugs of different types leads to activation of apoptosis, often through interactions with the transcription factor c-Myc and the tumor suppressor protein p53 [89]. A connection with c-Myc protein action was indicated in the proteomic study by Wilmes et al. [88], with c-Myc being decreased in abundance by peloruside A. Many of the off-target proteome changes either result from downstream effects on the primary target or effects on secondary targets, both of which could contribute to side effects of the drug in vivo.

2.4.3. Peloruside A binding site on tubulin

An interesting study by Pryor et al. in 2002, working with laulimalide, a relatively new MSA, showed that more than one binding site existed for the stabilizing compounds [90]. Laulimalide bound to a different site to that of the classic MSA’s, paclitaxel, epothilone, and discodermolide, which all bind to the well-described taxoid site on β-tubulin and can compete for each other’s binding [91,92]. Peloruside A was also shown to have a different binding site on the tubulin dimer to paclitaxel but was seen to bind to the same or an overlapping site with laulimalide [81]. This information on the peloruside A binding site was obtained through a collaboration beginning in 2004 beween Drs Miller and Northcote with two specialists in microtubule protein structure and function, Dr Fernando Díaz and Dr José Andreu of the Centro de Investigaciones Biológicas in Madrid. In a Flutax-2 (fluorescently-labeled paclitaxel derivative) displacement test using MALDI-TOF mass spectrometry, concentrations of up to 2,000-fold excess of peloruside A over Flutax-2 failed to displace Flutax-2 from the taxoid binding site; whereas, a 100-fold excess of paclitaxel could compete for the Flutax-2 binding completely. Laulimalide was also tested, and a 10-fold excess was found to compete for binding with peloruside A but not for Flutax-2 binding. Thus, peloruside A and laulimalide were proposed to have the same or an overlapping binding site [81]. Indirect evidence from this same study of a distinct binding site for peloruside A was its lack of sensitivity to resistance conferred by mutations to the taxoid binding site. Further work in collaboration with Dr Ernest Hamel at the National Cancer Institute (NCI/NIH) in Frederick, MD demonstrated that peloruside A could synergize with the taxoid site drugs in causing tubulin polymerization in vitro [93] and in cells [94], but peloruside A was unable to synergize with laulimalide, at least in vitro, thus, supporting the novel peloruside/laulimalide binding site on tubulin. The exact binding site on the tubulin dimer has still not been unequivocably identified at this stage, although a recent study using hydrogen-deuterium exchange mass spectrometry by Dr David Schriemer’s group in Calgary, Canada has proposed a peloruside A binding site on β-tubulin that is distinct from the taxane site [95]. Two previous studies that used computer docking also modeled the peloruside/laulimalide binding site, proposing it to be on α-tubulin rather than β-tubulin [96,97]. The question of an α- or β-tubulin binding site still needs to be resolved. It is possible of course that both binding sites exist, and further work is necessary in this area to settle this question. Dr Miller and Northcote are currently working with Dr Paraskevi Giannakakou at Weill Medical College of Cornell in New York City and Prof Jim Snyder at Emory University in Atlanta, using computer modeling and peloruside/laulimalide resistant cells to address this question.

At Victoria University of Wellington, experiments are also in progress with Dr David Bellows, a yeast geneticist, on the peloruside A binding site on yeast tubulin, taking advantage of the accessibility of the yeast genome and the ability to generate resistant mutants by site-directed mutagenesis [98]. The aim of this research is to map the peloruside A binding site by altering specific amino acids in yeast tubulin. Similar types of experiments on the taxoid binding site have been carried out by Prof Richard Himes’ group at the University of Kansas [99,100]. It was found that paclitaxel was unable to bind to yeast tubulin without humanization of the taxoid site sequence by converting five amino acids to those found in the human tubulin gene. Chemical genetics offers a new, exciting opportunity for identification of the targets of novel marine drugs, since chemical genetic screens are relatively easy to carry out in yeast, using genome-wide synthetic lethal arrays [101,102]. There is significant homology between yeast and mammalian cells, and a target identified in yeast has a good chance of having a homolog in mammalian systems. Similar types of screens in mammalian cells are possible using siRNA gene silencing techniques [103,104]. Whitehurst et al. looked at the effects of paclitaxel on growth of a human non-small-cell lung cancer cell line and interestingly identified α-tubulin as one of its hits, although its binding site is on β-tubulin, and also a number of proteasome genes. Network analysis from genome-wide screens has introduced the interesting possibility that drugs may target networks rather than single proteins [105,106], and this concept to some extent may help explain the multiple effects seen when a single drug is added to cells.

Paclitaxel is known to bind to the β-subunit of the microtubule at the taxoid binding site situated in a pocket lined by several hydrophobic residues [91,92,107]. The pocket is at the boundary between the nucleotide-binding domain and the middle domain of β-tubulin, and is in contact with the M-loop of tubulin. Paclitaxel greatly inhibits the peeling apart of protofilaments, suggesting that it stabilizes the microtubule through strengthening lateral interactions between the strands. Another possibility is that paclitaxel reduces the ability of protofilaments to curl, a process that occurs normally. A third possibility is that paclitaxel stabilizes the conformation of tubulin, stopping the movement of the nucleotide-binding domain against the central tubulin domain. Recent hydrogen-deuterium exchange mass spectrometry studies with discodermolide and chicken tubulin by Prof. Susan Horwitz’s group at Albert Einstein College of Medicine in New York have predicted a different conformation and stabilization mechanism to paclitaxel, although both bind in the same region [107]. Unlike paclitaxel, discodermolde does not bind to the M-loop but is turned toward the N-terminal H1-S2 loop on the opposite side of the taxane binding pocket which is proposed to be involved in the lateral contact between protofilaments. Although both drugs stabilize the interdimer and interprotofilament interactions, the mechansim of the interaction thus differs, with discodermolide having a greater effect on the interdimer interactions [107]. The conformational changes resulting from the different interdimer stabilizations share the potential to counteract the curvature of protofilaments, thus stabilizing the polymer. Since chicken tubulin has some amino acid differences from human or bovine tubulin in or close to the region of the taxoid binding site [108], there may be differences in the detailed interactions of paclitaxel and discodermolide with amino acids to those occurring in binding to mammalian tubulin.

In 2008, Huzil et al. [95] suggested that the mechanism of microtubule stabilization by peloruside A differs from stabilization by these taxoid-site drugs. This is not surprising, given its distinct binding site. Taxoid-site drugs interact with the βH7 region (bottom of the taxoid-binding cleft) that lies next to the T5 loop at the exchangeable nucleotide binding region; whereas, peloruside A interacts with the H9-S8 loop at the proposed binding site of peloruside A [95]. This binding site also lies next to the T5 loop. A conformational change in the T5 loop is believed to promote improved interactions across the interdimer interface, causing stabilization.

2.4.4. Peloruside congeners and analogues

In addition to work with natural congeners, including peloruside B (7) (Figure 1) [109], which has similar bioactivity to peloruside A, studies are in progress on semi-synthetic modifications to the structure of peloruside A. Opening of the pyranose ring of peloruside A by sodium borohydride reduction increased the IC₅₀ for cell growth inhibition by 26-fold in a murine leukocyte cell line (32D) [39]. Attempts to modify peloruside A and attach a fluorescent or radioactive label have not been overly successful due to the complexity of the molecule. Recently, however, a tritiated derivative of peloruside A has been prepared. Dr Ernest Hamel at NCI/NIH has used this ³H-peloruside A to examine competitive binding to microtubules (personal communication, 2010). Some modifications to the C-24 side chain have been carried out, and the activity of the side chain analog is currently under investigation in the laboratories of Drs Miller and Northcote, Dr Díaz, and Prof Ian Paterson in the Chemistry Department at the University of Cambridge.

2.4.5. Anti-disease potential of peloruside A

Peloruside A is currently under development as an anti-cancer drug through an agreement between Victoria University of Wellington and REATA Pharmaceuticals Inc., Dallas, Texas. Victoria University holds the patent on peloruside A [110]. Peloruside A has some promising advantages over paclitaxel, being more soluble and therefore not requiring the use of Cremophore EL, a polyoxyethylated castor oil, to deliver the drug to the body. This should correlate with fewer vehicle-associated side effects than paclitaxel [78]. Peloruside A is also more likely to be effective against cells that acquire the multiple-drug resistance (MDR) phenotype, since peloruside A remains active in cells with high P-glycoprotein drug efflux pump expression [81]. The resistance ratio of peloruside A in cells with an MDR phenotype to wild type cells was 21 in this study, compared with 1417 for paclitaxel [81]. Tests of peloruside A in animals have been very promising, with peloruside A showing no overt toxicity in mice and being more efficacious in inhibiting tumor growth than paclitaxel and docetaxel [111].

Recent work with a mouse model of multiple sclerosis (experimental autoimmune encephalomyelitis) by Dr Anne La Flamme at Victoria University of Wellington has demonstrated that peloruside A is as effective as paclitaxel at delaying the onset of the disease but, unlike paclitaxel, shows no toxicity [112]. Work has also begun at Victoria University of Wellington on the effect of peloruside A on microtubule-associated proteins and the potential value of the compound for the treatment of neurodegeneratory diseases like Alzheimer’s disease. Studies with MSA’s have already shown promise in this area since paclitaxel treatment can rescue motor function in animals with loss of tau protein activity [113].

At the present time, preclinical studies and the advancement of peloruside A into Phase I clinical trials for cancer therapy are being held back due to the short supply of natural and synthetic peloruside A. Attempts to aquaculture Mycale hentscheli in New Zealand coastal waters were initially very successful [19,20], but later were discontinued as a result of devastation of the sponge cultures by invading nudibranchs. An interesting finding from the aquaculture studies was that individual sponge samples that have good levels of peloruside A maintained those high levels in culture; whereas, samples that originally lacked peloruside A never acquired the ability to produce peloruside A, even when cultured in close proximity to peloruside A-producing sponges.

The De Brabander group at the University of Texas Southwestern was the first to carry out a total synthesis of peloruside A [114]. This first synthesis produced the inactive enantiomer of peloruside A, but the group subsequently re-synthesized the correct, bioactive enantiomer. Since then, three other laboratories have synthesized the compound in milligram amounts [115–117]. The synthetic strategies for peloruside A have been reviewed by Williams et al. [118]. A congener of peloruside A, peloruside B (7), has recently been synthesized by the Ghosh laboratory at Purdue University [109].

2.5. Zampanolide 2.5.1. Discovery and synthesis

After having worked on peloruside A for over 10 years, in 2009 Dr Northcote along with his PhD student Jonathan Singh found another sponge natural product, zampanolide (2) (Figure 1) in a collection of sponges taken from an underwater cave off the Tongan coast. The sponge, Cacospongia mycofijiensis (Figure 4), generated a number of different bioactive compounds, all of which had been described previously, including laulimalide and isolaulimalide (MSA’s), latrunculin A (an actin-destabilizing agent), dendrolasin (also isolated from insects and having pheromone activity), mycothiazole (function unknown), and zampanolide (function unknown at the time). Three Japanese chemists from Okinawa and Kyoto had just published a paper describing the synthesis and isolation of zampanolide from the sponge Fasciospongia rimosa [119]. Tanaka and Higa, however, were the first to describe the structure of zampanolide thirteen years earlier [120]. This 20-membered macrolide has potent, low nanomolar inhibitory activity on cell growth. Amos Smith, III at the University of Pennsylvania also published a total synthesis of the enantiomer of zampanolide [121].

2.5.2. Mode of action

Since zampanolide was a very potent bioactive compound with an IC₅₀ for growth inhibition in the low nanomolar range, Drs Miller and Northcote decided to have a look at its mechanism of action. As luck would have it, a simple flow cytometry experiment carried out at Victoria University of Wellington by Dr Miller’s graduate student Jessica Field (Figure 5) showed a clear block in the G₂/M phase of the cell cycle, suggesting an anti-mitotic action and a possible cytoskeletal target, either microtubules or microfilaments. It was also possible, of course, that the new compound interacted with a regulator of cell division, such as a cdc kinase or other mitotic regulatory protein; thus, there was no guarantee that its mode of action would be easily solved.

After the earlier groundwork with the MSA peloruside A in the Miller and Northcote laboratories, further experiments were carried out to check cytoskeletal activity of zampanolide, and the target was fairly quickly singled out as the microtubule. Confirmation that zampanolide was a new MSA was subsequently demonstrated by testing for intracellular polymerization of tubulin in cultured cells, the induction of microtubule bundling in interphase cells, and the generation of multiple asters and micronuclei during mitotic division. Finally, zampanolide was shown to promote extracellular tubulin assembly with purified bovine tubulin in the absence of added microtubule-associated proteins. The confirmed microtubule-stabilizing mode of action of zampanolide and the isolation and purification details were then published in the Journal of Medicinal Chemistry [122] less than six months after the Uenishi et al. paper describing the isolation and synthesis of zampanolide appeared on-line in 2009 [119]. It was also reported in the Field et al. [122] paper that overexpression of the P-glycoprotein (P-gp) drug efflux pump had no effect on the potency of zampanolide; hence, zampanolide remained effective in cells with an MDR phenotype, an important property for new generation MSA’s destined for clinical development. The other immediate promising characteristic of zampanolide, seen in its structure (Figure 1), was its reduced number of stereogenic centers compared to other MSA’s. Its simplified chemical structure suggested that a scale-up of the reported synthetic protocols [119–121,123–127] would be easier and less costly than for other MSA macrolides, and would improve its chances for entry into clinical trials. Further characterization of zampanolide is now underway at Victoria University of Wellington, the Díaz laboratory in Madrid, the Hamel laboratory at NCI/NIH in Maryland, and the Horwitz laboratory at Albert Einstein in New York to determine whether it binds to the taxoid site on tubulin, the laulimalide/peloruside site, or to a third site not previously described.

3. Conclusions

The newest members of the microtubule-stabilizing class of drugs, the pelorusides and zampanolide, show good potential for future development as anti-cancer drugs, and further characterization of their unique activity profiles is underway. The sponges from which these drugs were extracted also produce many other bioactive compounds with differing modes of action, including the mycalamides and pateamine, and thus, marine sponges remain an excellent source of bioactive compounds for potential development as pharmaceuticals for the treatment of cancer and other diseases.

Acknowledgements

We acknowledge all our invaluable collaborators and all the hard work and insights put in over the years by our graduate students who are too many to include as co-authors on this paper but deserve to be included (in chronological order): Lyndon West, Kylie Hood, Mike Page, Berber Rouwé, Thomas Gaitanos, Kevin Crume, Anja Wilmes, Ariane Chan, Arun Kanakkanthara, David O’Sullivan, Reem Hanna, Jessica Field, and Viswanath Das. Jonathan Singh is a current PhD student of Peter T. Northcote’s and has been instrumental in the isolation and purification of both pelorusides A and B and zampanolide.

References 1

Paterson

Anderson

The renaissance of natural products as drug candidates

Science2005310451453

10.1126/science.1116364

16239465

Newman

Cragg

Natural products as sources of new drugs over the last 25 years

J Nat Prod200770461477

10.1021/np068054v

17309302

Molinski

Dalisay

Lievens

Saludes

Drug development from marine natural products

Nat Rev Drug Discov200986985

10.1038/nrd2487

19096380

Cragg

Grothaus

Newman

Impact of natural products on developing new anti-cancer agents

Chem Rev200910930123043

10.1021/cr900019j

19422222

Sashidara

White

Crews

A selective account of the effective paradigms and significant outcomes in the discovery of inspirational marine natural products

J Nat Prod200972588603

10.1021/np800817y

19209899

Napolitano

Daranas

Norte

Fernández

Marine macrolides, a promising source of antitumor compounds

Anti-Cancer Agents Med Chem20099122137

10.2174/187152009787313800

Blunt

Copp

W-P

Munro

MHG

Northcote

Prinsep

Marine natural products

Nat Prod Rep200926170244and previous reviews in this series

10.1039/b805113p

19177222

Belarbi

Contreras

Gomez A

Chisti

García Camacho

Molina Grima

Producing drugs from marine sponges

Biotechnol Adv200321585598

14516872

Haefner

Drugs from the deep: Marine natural products as drug candidates

Drug Discov Today20098536544 10

Mestel

Drugs from the sea

Discover1999March7174 11

Simmons

Andrianasolo

McPhail

Flatt

Gerwick

Marine natural products as anticancer drugs

Mol Cancer Ther20054333342

15713904

Singh

Sharma

Joshi

Rawat

Clinical status of anti-cancer agents derived from marine sources

Anticancer Agents Med Chem20088603617

18690825

Sipkema

Franssen

MCR

Osinga

Tramper

Wijffels

Marine sponges as pharmacy

Mar Biotech20057142162

10.1007/s10126-004-0405-5

Flam

Chemical prospectors scour the seas for promising drugs

Science199426613241325

10.1126/science.7973722

7973722

Davidson

New dimensions in natural products research: cultured marine microorgansims

Curr Opin Biotech19956284291

10.1016/0958-1669(95)80049-2

Bentley

Microbial secondary metabolites play important roles in medicine: Prospects for discovery of new drugs

Perspect Biol Med199740364395

9167261

Bewley

Faulkner

Lithistid sponges: Star performers or hosts to the stars

Angew Chem Int Ed19983721622178

10.1002/(SICI)1521-3773(19980904)37:16<2162::AID-ANIE2162>3.0.CO;2-2

Fusetani

Kem

Marine toxins: an overview

Prog Mol Subcell Biol200946144

19184583

Page

West

Northcote

Battershill

Kelly

Spatial and temporal variability of cytotoxic metabolites in populations of the New Zealand sponge Mycale hentscheli

J Chem Ecol20053111611174

10.1007/s10886-005-4254-0

16124239

Page

Northcote

Webb

Mackey

Handley

Aquaculture trials for the production of biologically active metabolites in the New Zealand sponge Mycale hentscheli (Demospongiae: Poecilosclerida)

Aquaculture2005250256269

10.1016/j.aquaculture.2005.04.069

Jordan

Wilson

Microtubules and actin filaments: dynamic targets for cancer chemotherapy

Curr Opin Cell Biol199810123130

10.1016/S0955-0674(98)80095-1

9484604

Jordan

Wilson

Microtubules as a target for anticancer drugs

Nat Rev Cancer20044253265

10.1038/nrc1317

15057285

Zhou

Giannakakou

Targeting microtubules for cancer chemotherapy

Curr Med Chem–Anti-Cancer Agents200556571

10.2174/1568011053352569

Altmann

Gertsch

Anticancer drugs from nature—natural products as a unique source of new microtubule-stabilizing agents

Nat Prod Rep200724327357

10.1039/b515619j

17390000

Kingston

DGI

Tubulin-interactive natural products as anticancer agents

J Nat Prod200972507515

10.1021/np800568j

19125622

Saito

Toxins affecting actin filaments and microtubules

Prog Mol Subcell Biol200946187219

19184589

Rowinsky

Donehower

Paclitaxel (Taxol)

New Engl J Med199533210041014

10.1056/NEJM199504133321507

7885406

Rowinsky

Calvo

Novel agents that target tublin and related elements

Semin Oncol200633421435

10.1053/j.seminoncol.2006.04.006

16890797

Morris

Fornier

Microtubule active agents: Beyond the taxane frontier

Clin Cancer Res20081471677172

10.1158/1078-0432.CCR-08-0169

19010832

Wani

Taylor

Wall

Coggon

McPhail

Plant antitumor agents. VI. The isolation and structure of Taxol, a novel antileukemic and antitumor agent from Taxus brevifolia

J Am Chem Soc19719323252327

10.1021/ja00738a045

5553076

Schiff

Fant

Horwitz

Promotion of microtubule assembly in vitro by Taxol

Nature1979277665667

10.1038/277665a0

423966

Tinley

Randall-Hlubek

Leal

Jackson

Cessac

Quada

JrHemscheidt

Mooberry

Taccalonolides E and A: Plant-derived steroids with microtubule-stabilizing activity

Cancer Res20036332113220

12810650

Bollag

McQueney

Zhu

Hensens

Koupal

Leisch

Goetz

Lazarides

Woods

Epothilones, a new class of microtubule-stabilizing agents with a Taxol-like mechanism of action

Cancer Res19955523252333

7757983

Lindel

Jensen

Fenical

Long

Casazza

Carboni

Fairchild

Eleutherobin, a new cytotoxin that mimics paclitaxel (Taxol) by stabilizing microtubules

J Am Chem Soc199711987448745

10.1021/ja9717828

Long

Carboni

Wasserman

Cornell

Casazza

Jensen

Lindel

Fenical

Fairchild

Eleutherobin, a novel cytotoxic agent that induces tubulin polymerisation, is similar to paclitaxel (Taxol)

Cancer Res19985811111115

9515790

D’Ambrosio

Guerriero

Pietra

Sarcodictyin A and sarcodictyin B, novel diterpenoidic alcohols esterified by (E)-N(1)-methylurocanic acid. Isolation from the Mediterranean stolonifer Sarcodictyon roseum

Helv Chim Acta19877020192027

10.1002/hlca.19870700807

Hamel

Sackett

Vourloumis

Nicolaou

The coral-derived natural products eleutherobin and sarcodictyins A and B: Effects on the assembly of purified tubulin with and without microtubule-associated proteins and binding at the polymer taxoid site

Biochemistry19993854905498

10.1021/bi983023n

10220336

Hood

West

Northcote

Berridge

Miller

Induction of apoptosis by the marine sponge (Mycale) metabolites, mycalamide A and pateamine

Apoptosis20016207219

10.1023/A:1011340827558

11388670

Hood

Bäckström

West

Northcote

Berridge

Miller

The novel cytotoxic sponge metabolite peloruside A, structurally similar to bryostatin-1, has unique bioactivity independent of protein kinase C

Anti-Cancer Drug Des200116155166 40

Miller

Rouwé

Gaitanos

Hood

Crume

Bäckström

La Flamme

Berridge

Northcote

Peloruside A enhances apoptosis in H-ras-transformed cells and is cytotoxic to proliferating T cells

Apoptosis20049785796

10.1023/B:APPT.0000045789.54694.cf

15505421

Perry

Blunt

Munro

MHG

Mycalamide A, an antiviral compound from a New Zealand sponge of the genus

Mycale J Am Chem Soc198811048504851

10.1021/ja00222a067

Perry

Blunt

Munro

MHG

Thompson

Antiviral and antitumor agents from a New Zealand sponge, Mycale sp. 2. Structures and solution conformations of mycalamides A and B

J Org Chem199055223227

10.1021/jo00288a037

West

Northcote

Hood

Miller

Page

Mycalamide D, a new cytotoxic amide from the New Zealand marine sponge Mycale species

J Nat Prod200063707709

10.1021/np9904511

10843597

Simpson

Garson

Blunt

Munro

MHG

Hooper

JNA

Mycalamides C and D, cytotoxic compounds from the marine sponge Stylinos n. species

J Nat Prod200063704706

10.1021/np990431z

10843596

Cardani

Ghiringhelli

Mondelli

Quilico

The structure of pederin

Tetrahedron Lett1965625372545

10.1016/S0040-4039(01)84020-X

Soldati

Fioretti

Ghione

Cytotoxicity of pederin and some of its derivatives on cultured mammalian cells

Experientia196622176178

10.1007/BF01897720

5959934

Kellner

RLL

Dettner

Differential efficacy of toxic pederin in deterring potential arthropod predators of Paederus (Coleoptera: Staphylinidae) offspring

Oecologia1996107293300

10.1007/BF00328445

Sakemi

Ichiba

Kohmoto

Saucy

Isolation and structure elucidation of onnamide A, a new bioactive metabolite of a marine sponge, Theonella sp

J Am Chem Soc198811048514853

10.1021/ja00222a068

Matsunaga

Fusetani

Nakao

Eight new cytotoxic metabolites closely related to onnamide A from two marine sponges of the genus Theonella

Tetrahedron19924883698376

10.1016/S0040-4020(01)86585-6

Kobayashi

Itagaki

Shigemori

Sasaki

Three new onnamide congeners from the Okinawan marine sponge Theonella sp

J Nat Prod199356976981

10.1021/np50096a030

Vuong

Capon

Lacey

Gill

Heiland

Friedel

Onnamide F: A new nematocide from a Southern Australian marine sponge Trachycladus laevispirulifer

J Nat Prod200164640642

10.1021/np000474b

11374963

Fusetani

Sugawara

Matsunaga

Theopederins A–E, potent antitumor metabolites from a marine sponge, Theonella sp

J Org Chem19925738283832

10.1021/jo00040a021

Tsukamoto

Matsunaga

Fusetani

Toh-e

Theopederins F-J: Five new antifungal and cytotoxic metabolites from the marine sponge Theonella swinhoei

Tetrahedron1999551369713702

10.1016/S0040-4020(99)00841-8

Paul

Gunasekera

Longley

Pomponi

Theopederins K and L. Highly potent cytotoxic metabolites from a marine sponge Discodermia species

J Nat Prod2002655961

10.1021/np0103766

11809067

Burres

Clement

Antitumor activity and mechanism of action of the novel marine natural products mycalamide-A and -B and onnamide

Cancer Res19894929352940

2720652

Carrasco

Fernandez-Puentes

Vazques

Antibiotics and compounds affecting translation by eukaryotic ribosomes. Specific enhancement of aminoacyl-tRNA binding by methylxanthines

Mol Cell Biochem19761097122

10.1007/BF01742203

768741

Abell

Blunt

Foulds

Munro

MHG

Chemistry of the mycalamides: antiviral and antitumor compounds from a New Zealand marine sponge. Part 6. The synthesis and testing of analogues of the C(7)–C(10) fragment

J Chem Soc Perkin Trans 1199716471654 58

Gürel

Blaha

Steitz

Moore

Structures of triacetyloleandomycin and mycalamide A bind to the large ribosomal subunit of Haloarcula marismortui

Antimicrob Agents Chemother20095350105014

10.1128/AAC.00817-09

19738021

Hong

Kishi

Total synthesis of mycalamides A and B

J Org Chem19905542424245

10.1021/jo00301a007

Roush

Pfeifer

Total synthesis of mycalamide A and 7-epi-mycalamide A

Org Lett20002859862

10.1021/ol005629l

10754688

Sohn

J-H

Waizumi

Zhong

Rawal

Total synthesis of mycalamide A

J Am Chem Soc200512772907291

10.1021/ja050728l

15898759

Kagawa

Ihara

Toyota

Convergent total synthesis of (+)-mycalamide A

J Org Chem20067167966805

10.1021/jo060803q

16930029

Kagawa

Ihara

Toyota

Total synthesis of (+)-mycalamide A

Org Lett20068875878

10.1021/ol052943c

16494463

Thompson

Blunt

Munro

MHG

Perry

Pannell

Chemistry of the mycalamides, antiviral and antitumour compounds from a marine sponge. Part 3. Acyl, alkyl and silyl derivatives

J Chem Soc, Perkin Trans 1199213351342 65

Thompson

Blunt

Munro

MHG

Clark

Chemistry of the mycalamides, antiviral and antitumour compounds from a marine sponge. Part 4. Reactions of mycalamide A and alkyl derivatives with basic nucleophiles

J Chem Soc, Perkin Trans 1199410251031 66

Thompson

Blunt

Munro

MHG

Perry

Chemistry of the mycalamides, antiviral and antitumor compounds from a marine sponge. Part 5. Acid-catalysed hydrolysis and acetal exchange, double bond additions and oxidation reactions

J Chem Soc, Perkin Trans 1199512331242 67

Fukui

Tsuchiya

Fujita

Nakagawa

Koshino

Nakata

Synthesis and biological activity of artificial analogs of mycalamide A

Bioorg Med Chem Lett1997720812086

10.1016/S0960-894X(97)00365-X

Richter

Kocienski

Raubo

Davies

The in vitro biological activities of synthetic 18-O-methyl mycalamide B, 10-epi-18-O-methyl mycalamide B and pederin

Anticancer Drug Des199712217227

9154112

Northcote

Blunt

Munro

MHG

Pateamine: a potent cytotoxin from the New Zealand marine sponge, Mycale sp

Tetrahedron Lett19913264116414

10.1016/0040-4039(91)80182-6

Romo

Rzasa

Shea

Park

Langenhan

Sun

Akhiezer

Liu

Total synthesis and immunosuppressive activity of (−)-pateamine A and related compounds: Implementation of a β-lactam-based macrocyclization

J Am Chem Soc19981201223712254

10.1021/ja981846u

Licitra

Liu

A three-hybrid system for detecting small ligand-protein receptor interactions

Proc Nat Acad Sci USA1996931281712821

10.1073/pnas.93.23.12817

8917502

Bordeleau

Matthews

Wojnar

Lindqvist

Novac

Jankowsky

Sonenberg

Northcote

Teesdale-Spittle

Pelletier

Stimulation of mammalian translation initiation factor eIF4A activity by a small molecule inhibitor of eukaryotic translation

Proc Nat Acad Sciences USA20051021046010465

10.1073/pnas.0504249102

Low

Dang

Schneider-Poetsch

Shi

Choi

Merrick

Romo

Liu

Inhibition of eukaryotic translation initiation by the marine natural product pateamine A

Mol Cell200520709722

10.1016/j.molcel.2005.10.008

16337595

Low

Dang

Schneider-Poetsch

Shi

Choi

Rzasa

Shea

Park

Romo

Liu

Isolation and identification of eukaryotic initiation factor 4A as a molecular target for the marine natural product Pateamine A

Meth Enzymol2007431303324

17923240

Dang

Low

Gehring

Dietz

Romo

Liu

Inhibition of nonsense-mediated mRNA decay by the natural product pateamine A through eukaryotic initiation factor 4AIII

J Biol Chem20092842361323621

10.1074/jbc.M109.009985

19570977

West

Northcote

Battershill

Peloruside A: A potent cytotoxic macrolide isolated from the New Zealand marine sponge Mycale sp

J Org Chem200065445449

10.1021/jo991296y

10813954

Hood

West

Rouwé

Northcote

Berridge

Wakefield

StJ

Miller

Peloruside A, a novel anti-mitotic agent with paclitaxel-like microtubule-stabilizing activity

Cancer Res20026233563360

12067973

Rowinsky

Eisenhauer

Chaudhry

Arbuck

Donehower

Clinical toxicities encountered with paclitaxel (Taxol)

Semin Oncol199320115

8290966

Horwitz

Personal recollections on the early development of Taxol

J Nat Prod200467136138

10.1021/np0304464

14987047

Díaz

Andreu

Assembly of purified GDP-tubulin into microtubules induced by Taxol and Taxotere: Reversibility, ligand stoichiometry, and competition

Biochemistry19933227472755

10.1021/bi00062a003

8096151

Gaitanos

Buey

Díaz

Northcote

Teesdale-Spittle

Andreu

Miller

Peloruside A does not bind to the taxoid site on β-tubulin and retains its activity in multidrug resistant cell lines

Cancer Res20046450635067

10.1158/0008-5472.CAN-04-0771

15289305

Kowalski

Giannakakou

Gunasekera

Longley

Day

Hamel

The microtubule-stabilizing agent discodermolide competitively inhibits the binding of paclitaxel (Taxol) to tubulin polymers, enhances tubulin nucleation reactions more potently than paclitaxel, and inhibits the growth of paclitaxel-resistant cells

Mol Pharmacol199752613622

9380024

Yvon

AMC

Wadsworth

Jordan

Taxol suppresses dynamics of individual microtubules in living human tumor cells

Mol Biol Cell199910947959

10198049

Kamath

Jordan

Suppression of microtubule dynamics by epothilone B is associated with mitotic arrest

Cancer Res20036360266031

14522931

Honore

Kamath

Braguer

Wilson

Briand

Jordan

Suppression of microtubule dynamics by discodermolide by a novel mechanism is associated with mitotic arrest and inhibition of tumor cell proliferation

Mol Cancer Ther2003213031311

14707271

Honore

Kamath

Braguer

Horwitz

Wilson

Briand

Jordan

Synergistic suppression of microtubule dynamics by discodermolide and paclitaxel in non-small cell lung carcinoma cells

Cancer Res20046449574964

10.1158/0008-5472.CAN-04-0693

15256469

Chan

Andreae

Northcote

Miller

Peloruside A inhibits microtubule dynamics in a breast cancer cell line MCF7

Invest New Drugs2010

10.1007/s10637-010-9398-2

Wilmes

Rawson

Peng

McLauchlan

Northcote

Jordan

Miller

Effects of the microtubule stabilizing agent peloruside A on the proteome of HL-60 cells

Invest New Drugs2010

10.1007/s10637-010-9387-5

Hermeking

Eick

Mediation of c-Myc-induced apoptosis by p53

Science199426520912093

10.1126/science.8091232

8091232

Pryor

O’Brate

Bilcer

Díaz

Wang

Kabaki

Jung

Andreu

Ghosh

Giannakakou

Hamel

The microtubule stabilizing agent laulimalide does not bind in the taxoid site, kills cells resistant to paclitaxel and epothilones, and may not require its epoxide moiety for activity

Biochemistry20024191099115

10.1021/bi020211b

12119025

Nogales

Wolf

Khan

Ludueña

Downing

Structure of tubulin at 6.5 Å and location of the taxol-binding site

Nature1995375424427

10.1038/375424a0

7760939

Downing

Structural basis for the interaction of tubulin with proteins and drugs that affect microtubule dynamics

Annu Rev Cell Dev Biol20001689111

10.1146/annurev.cellbio.16.1.89

11031231

Hamel

Day

Miller

Jung

Northcote

Ghosh

Curran

Cushman

Nicolaou

Paterson

Sorensen

Synergistic effects of peloruside A and laulimalide with taxoid site drugs, but not with each other, on tubulin assembly

Mol Pharmacol20067015551564

10.1124/mol.106.027847

16887932

Wilmes

Bargh

Kelly

Northcote

Miller

Peloruside A synergizes with other microtubule stabilizing agents in cultured cancer cell lines

Mol Pharm20074269280

10.1021/mp060101p

17397239

Huzil

Chik

Slysz

Freedman

Tuszynski

Taylor

Sackett

Schriemer

A unique mode of microtubule stabilization induced by peloruside A

J Mol Biol200837810161030

10.1016/j.jmb.2008.03.026

18405918

Pineda

Farràs

Maccari

Manetti

Botta

Vilarrasa

Computational comparison of microtubule-stabilizing agents laulimalide and peloruside with taxol and colchicine

Bioorg Med Chem Lett20041448254829

10.1016/j.bmcl.2004.07.053

15341932

Jiménez-Barbero

Canales

Northcote

Buey

Andreu

Díaz

NMR determination of the bioactive conformation of peloruside A bound to microtubules

J Am Chem Soc200612887578765

10.1021/ja0580237

16819869

Barberis

Gunde

Berset

Audetat

Lüthi

Yeast as a screening tool

Drug Discov Today: Technol20052187192

10.1016/j.ddtec.2005.05.022

Bode

Gupta

JrReiff

Suprenant

Georg

Himes

Epothilone and paclitaxel: unexpected differences in promoting the assembly and stabilization of yeast microtubules

Biochemistry20024138703874

10.1021/bi0121611

11900528

100

Gupta

JrBode

Georg

Himes

Understanding tubulin-Taxol interactions: Mutations that impart Taxol binding to yeast tubulin

Proc Nat Acad Sci USA200310063946397

10.1073/pnas.1131967100

12740436

101

Tong

AHY

Evangelista

Parsons

Bader

Pagé

Robinson

Raghibizadeh

Hogue

CWV

Bussey

Andrews

Tyers

Boone

Systematic genetic analysis with ordered arrays of yeast deletion mutants

Science200129423642368

10.1126/science.1065810

11743205

102

Giaever

Flaherty

Kumm

Proctor

Nislow

Jaramillo

Chu

Jordan

Arkin

Davis

Chemogenomic profiling: Identifying the functional interactions of small molecules in yeast

Proc Nat Acad Sci USA2004101793798

10.1073/pnas.0307490100

14718668

103

Vanhecke

Janitz

High-throughput gene silencing using cell arrays

Oncogene20042383538358

10.1038/sj.onc.1208027

15517016

104

Whitehurst

Bodemann

Cardenas

Ferguson

Girard

Peyton

Minna

Michnoff

Hao

Roth

Xie

White

Synthetic lethal screen identification of chemosensitizer loci in cancer cells

Nature2007446815819

10.1038/nature05697

17429401

105

Schadt

Friend

Shaywitz

A network view of disease and compound screening

Nat Rev Drug Discov20098286295

10.1038/nrd2826

19337271

106

Costanzo

Baryshnikova

Bellay

Kim

Spear

Sevier

Ding

Koh

JLY

Toufighi

Mostafavi

The genetic landscape of a cell

Science2010327425431

10.1126/science.1180823

20093466

107

Khrapunovich-Baine

Menon

Verdier-Pinard

Smith

IIIAngeletti

Fiser

Horwitz

Xiao

Distinct pose of discodermolide in taxol binding pocket drives a complementary mode of microtubule stabilization

Biochemistry2009481166411677

10.1021/bi901351q

19863156

108

Xiao

Verdier-Pinard

Fernandez-Fuentes

Burd

Angeletti

Fiser

Horwitz

Orr

Insights into the mechanism of microtubule stabilization by Taxol

Proc Nat Acad Sci USA20061031016610173

10.1073/pnas.0603704103

16801540

109

Singh

West

Wilmes

Chan

Hamel

Miller

Northcote

Ghosh

Peloruside B, a potent antitumor macrolide from the New Zealand marine sponge Mycale hentscheli: Isolation, structure, total synthesis and bioactivity

J Org Chem201075210

10.1021/jo9021265

19957922

110

Northcote

Miller

West

Hood

Bioactive compound (Peloruside A)

US Patent Number US6,790,862 B2September142004 111

Meyer

Ferguson

Krauth

Wick

Northcote

RTA 301 (peloruside): a novel microtubule stabilizer with potent in vivo activity against lung cancer and resistant breast cancer

18th EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics

Prague, Czech Republic

November 7–10, 2006

Abstr No. 639. Available online: http://www.sciencedirect.com/science/article/B75GT-4MMF4DM-ST/2/901656de391d50b1ced2b7ad843d922a

10.1016/S1359-6349(06)70644-9

112

Crume

O’Sullivan

Miller

Northcote

La Flamme

Delaying the onset of experimental autoimmune encephalomyelitis with the microtubule-stabilizing compounds, paclitaxel and peloruside A

J Leukocyte Biol200986949958

10.1189/jlb.0908541

19654226

113

Brunden

Trojanowski

Lee

VM-Y

Advances in tau-focused drug discovery for Alzheimer’s disease and related tauopathies

Nat Rev Drug Discov20098783793

10.1038/nrd2959

19794442

114

Liao

De Brabander

Total synthesis of peloruside A

Angew Chem Int Ed20034216481652

10.1002/anie.200351145

115

Jin

Taylor

Total synthesis of (+)-peloruside A

Org Lett2005713031305

10.1021/ol050070g

15787492

116

Ghosh

Kim

Enantioselective total synthesis of peloruside A: a potent microtubule stabilizer

Org Lett20081010011004

10.1021/ol703091b

18247632

117

Evans

Welch

Speed

Moniz

Reichelt

An aldol-based synthesis of (+)-peloruside a, a potent microtubule stabilizing agent

J Am Chem Soc200913138403841

10.1021/ja900020a

19249829

118

Williams

Nag

Zorn

Strategies for the synthesis of the novel antitumor agent peloruside A

Curr Opin Drug Discov Devel200811251271

18283613

119

Uenishi

Iwamoto

Tanaka

Total synthesis of (−)-zampanolide and questionable existence of (−)-dactylolide as the elusive biosynthetic precursor of (−)-zampanolide in an Okinawan sponge

Org Lett20091132623265

10.1021/ol901167g

19586001

120

Tanaka

Higa

Zampanolide, a new cytotoxic macrolide from a marine sponge

Tetrahedron Lett19963755355538

10.1016/0040-4039(96)01149-5

121

Smith

IIISafonov

Corbett

Total syntheses of (+)-zampanolide and (+)-dactylolide exploiting a unified strategy

J Am Chem Soc20021241110211113

10.1021/ja020635t

12224958

122

Field

Singh

Kanakkanthara

Halafihi

Northcote

Miller

Microtubule-stabilizing activity of Zampanolide, a potent macrolide isolated from the Tongan marine sponge Cacospongia mycofijiensis

J Med Chem20095273287332

10.1021/jm901249g

19877653

123

Smith

IIISafonov

Corbett

Total synthesis of (+)-zampanolide

J Am Chem Soc20011231242612427

10.1021/ja012220y

11734051

124

Ding

Jennings

Total synthesis of (−)-dactylolide and formal synthesis of (−)-zampanolide via target oriented β-C-glycoside formation

J Org Chem20087359655976

10.1021/jo8009853

18588348

125

Ding

Jennings

An expedient total synthesis of (−)-dactylolide and formal synthesis of (−)-zampanolide

Org Lett2005723212324

10.1021/ol0504897

15932188

126

Hoye

Macrolactonization via Ti(IV)-mediated epoxy-acid coupling: a total synthesis of (−)-dactylolide [and zampanolide]

J Am Chem Soc200312595769577

10.1021/ja035579q

12904009

127

Jennings

Total Synthesis of (−)-dactylolide and formal synthesis of (−)zampanolide

Lett Org Chem200637881

10.2174/157017806775224206

Figures Figure 1

Structures of the compounds.

Figure 2

The marine sponge Mycale hentscheli collected from Pelorus Sound, New Zealand.

Figure 3

Peloruside A-induced tubulin polymerization in 1A9 ovarian carcinoma cells. Cells were treated with peloruside A and a supernatant and pellet fraction electrophoresed. The gel was immunoblotted for α-tubulin. Image supplied by Arun Kanakkanthara.

Figure 4

Cacospongia mycofijiensis, collected from Vava’u, Tonga. Photograph courtesy of Karen Stone, Dive Vava’u.

Figure 5

Effect of zampanolide on cell cycle progression using flow cytometry. HL-60 promyelocytic leukemic cells were treated with 4 nM zampanolide for 16 hr, stained with propidium iodide, and analyzed by flow cytometry. Graphs courtesy of Jessica Field.