Amy E. Wright

Tubulin polymerizing activity of dictyostatin-1, a polyketide of marine sponge origin.

Dictyostatin-1 had previously been isolated from a marine sponge of the genus Spongia sp. and described as a cytotoxic agent to murine and human cancer cells, but its mechanism of activity was unknown. In a routine screening assay used to detect cytotoxic compounds of marine origin, dictyostatin-1 was identified as a highly active component in an extract from a Lithistida sponge and exploration into its pharmacology was pursued. Initial studies demonstrated that dictyostatin-1 arrested cells in the G(2)/M phase of the cell cycle. Staining of these cells with antitubulin revealed cells having multiple aster formations and microtubule matrix bundling patterns similar to that seen in cells exposed to paclitaxel. Dictyostatin-1 was able to induce the polymerization of purified bovine brain tubulin in vitro and the polymerized tubulin remained stable at cold temperatures. Dictyostatin-1 also proved to be highly potent in two paclitaxel-resistant human cancer cell lines expressing active P-glycoprotein. Together, these results indicate that dictyostatin-1 is a potent inducer of tubulin polymerization and retains activity in cells expressing the P-glycoprotein efflux pump.

Leiodermatolide, a Potent Antimitotic Macrolide from the Marine Sponge Leiodermatium sp.

Leiodermatolide is a structurally unique macrolide, isolated from the deep-water marine sponge Leiodermatium sp., which exhibits potent antiproliferative activity against a range of human cancer cell lines (IC50 <10 nM) and dramatic effects on spindle formation in mitotic cells. Its unprecedented polyketide skeleton and stereochemistry were established using a combination of experimental and computational (DP4) NMR methods, and molecular modelling.

Stereochemical determination of dictyostatin, a novel microtubule-stabilising macrolide from the marine sponge Corallistidae sp.Electronic supplementary information (ESI) available: copies of 1D and 2D NMR spectra, tables of spectral data and calculated torsion angles. See http://www.rsc.org/suppdata/cc/b3/b316390c/

The relative stereochemistry of the 22-membered marine macrolide dictyostatin, a Taxol-like antimitotic agent, was determined based on a combination of extensive high field NMR studies, including J-based configuration analysis, and molecular modelling.

In Vitro CuIture of the Tropical Sponge Axinella corrugata (Demospongiae): Effect of Food Cell Concentration on Growth, Clearance Rate, and Biosynthesis of Stevensine

In vitro culture is one possible method for supplying sponge metabolites for pharmaceutical applications, but appropriate feeding regimens that maximize both growth and metabolite biosynthesis are largely unknown. According to the natural concentration (NC) of cells 1 to 50 µm in size that are available to wild Axinellacorrugata, we fed explants a multispecific diet of bacteria, microalgae, and yeast at 4 different concentrations: 1NC, 3NC, 5NC, and 5+1NC (the last consisted of 5 NC of bacteria and 1 NC of microalgae and yeast). Explants fed a 3NC diet had the best culture response, growing on average from 8.5 g to 10.3 g in 8 weeks, and showing a 110% increase in concentration (milligrams per gram of dry weight) of the antitumor compound stevensine. Stevensine production in 3NC explants, representing the total milligrams of metabolite per explant, increased by 157% over the study. Explants fed at 1NC had relatively stable weights, indicating that the diet met metabolic costs only. Explants fed at the two highest concentrations lost weight after 4 weeks, possibly because long-term high cell concentration blocked their aquiferous system, reducing their ability to feed efficiently. Stevensine production in explants fed the 1NC, 5NC, or 5+1NC diets were similar, and varied little from the initial amount. A separate experiment showed that the clearance rate for A. corrugata is similar between the examined food types and cell concentrations over 5 hours, averaging 766 ml h−1 g DW−1.Overall, this study demonstrates that relatively small changes in food abundance can greatly affect both sponge growth and metabolite biosynthesis. The good growth and increased production of the target metabolite stevensine for A. corrugata explants fed a 3NC diet suggests that in vitro culture is a viable method of supplying some sponge metabolites.

Eryloside F, a novel penasterol disaccharide possessing potent thrombin receptor antagonist activity

We report the discovery of Eryloside F, a novel disaccharide of the steroidal carboxylic acid penasterol, isolated from an extract of the marine sponge Erylus formosus. The compound is a potent thrombin receptor antagonist, and furthermore inhibits human platelet aggregation in vitro.

Eryloside E from an atlantic sponge Erylus goffrilleri

Abstract A glycoside, which we call eryloside E ( 1 ), was isolated from the marine sponge Erylus goffrilleri and characterized by spectroscopic methods. Eryloside E possesses a rare penasterol nucleus with a t -butyl substituent on the side chain and three sugar molecules attached through carbons 3 and 30.

Cytotoxic cembranoids from the gorgonian Pseudopterogorgia bipinnata

Abstract Four new cytotoxic cembranoids, denoted as bipinnatins a-d, have been isolated from the gorgonian coral Pseudopterogorgia bipinnata . Their structures were determined through a combination of spectroscopic and x-ray crystallographic methods.

The marine natural product manzamine A targets vacuolar ATPases and inhibits autophagy in pancreatic cancer cells.

Manzamine A, a member of the manzamine alkaloids, was originally isolated from marine sponges of the genus Haliclona. It was recently shown to have activity against pancreatic cancer cells, but the precise mechanism of action remained unclear. To further our understanding of the mechanism of action of manzamine A, chemogenomic profiling in the yeast S. cerevisiae was performed, suggesting that manzamine A is an uncoupler of vacuolar ATPases. Fluorescence microscopy confirmed this effect on yeast vacuoles, where manzamine A produced a phenotype very similar to that of the established v-ATPase inhibitor bafilomycin A1. In pancreatic cancer cells, 10 µM manzamine A affected vacuolar ATPase activity and significantly increased the level of autophagosome marker LC3-II and p62/SQSTM1 as observed by western blot analysis. Treatment with manzamine A in combination with bafilomycin A1 (inhibitor of autophagosome-lysosome fusion) did not change the levels of LC3-II when compared to cells treated with bafilomycin A1 alone, suggesting that manzamine A is a potential inhibitor of autophagy by preventing autophagosome turnover. As autophagy is essential for pancreatic tumor growth, blocking this pathway with manzamine A suggests a promising strategy for the treatment of pancreatic cancer.

A new sterol sulfate, Sch 572423, from a marine sponge, Topsentia sp.

Bioassay-guided fractionation of an active fraction from a marine sponge Topsentia sp. in our marine fraction library (MFL) led to the isolation and identification of halistanol sulfate (1) and a new sterol sulfate Sch 572423 (2). Compounds 1 and 2 were identified as P2Y(12) inhibitors with IC(50) of 0.48 and 2.2 microM, respectively. The general method of purification for the MFL library and the structure elucidation of compound 2 are described.

Total synthesis of a potent hybrid of the anticancer natural products dictyostatin and discodermolide

A potent dictyostatin-discodermolide hybrid was designed and synthesised; it showed enhanced cell growth inhibitory activity relative to discodermolide in four human cancer cell lines including the Taxol-resistant NCI/ADR-Res cell line.