title: Microfilament depletion and circumvention of multiple drug resistance by sphinxolides.
abstract: Sphinxolides, a newly described family of cytotoxins from the New Caledonian sponge Neosiphonia superstes, bear structural resemblance to scytophycins. We now demonstrate that the cytotoxicity of sphinxolides is associated with cell cycle arrest in G2-M and induction of apoptosis. Like scytophycins and cytochalasins, sphinxolides caused rapid loss of microfilaments in cultured cells, without affecting microtubule organization. Microfilament reassembly was very slow after removal of the sphinxolide, consistent with the slow recovery of cellular proliferation. Sphinxolides potently inhibited actin polymerization in vitro and the microfilament-dependent ATPase activity of purified actomyosin, indicating a direct effect on actin. Importantly, sphinxolides were equally cytotoxic toward MCF-7 human breast carcinoma cells and a subline which overexpresses P-glycoprotein (MCF-7/ADR). Similarly, overexpression of the multidrug resistance-associated protein MRP by HL-60 cells did not confer resistance to the sphinxolides. These studies demonstrate that sphinxolides are potent new antimicrofilament compounds that circumvent multidrug resistance mediated by overexpression of either P-glycoprotein or MRP. Therefore, these agents may be useful in the treatment of drug-resistant tumors.
authors.affiliation: Department of Pharmacology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: L
authors.initials: L
authors.lastname: Minale
authors.forename: A
authors.initials: A
authors.lastname: Zampella
authors.forename: C D
authors.initials: CD
authors.lastname: Smith
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects*; D000199:Actins / Q000187:drug effects / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000187:drug effects; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects*; D003571:Cytochalasin B / Q000494:pharmacology; D003603:Cytotoxins / Q000494:pharmacology*; D053938:DNA Fragmentation; D018432:Drug Resistance, Multiple; D004354:Drug Screening Assays, Antitumor; D018922:HL-60 Cells / Q000187:drug effects; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000648:ultrastructure; D011108:Polymers; D011161:Porifera / Q000737:chemistry*; D011714:Pyrans / Q000494:pharmacology; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D000199:Actins; D000970:Antineoplastic Agents; D003603:Cytotoxins; D011108:Polymers; D011714:Pyrans; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors; C068527:tolytoxin; D003571:Cytochalasin B; D000251:Adenosine Triphosphatases