Abstract
Disorazoles comprise a family of 29 macrocyclic polyketides isolated from the fermentation broth of the myxobacterium Sorangium cellulosum. The major fermentation product, disorazole A1, was found previously to irreversibly bind to tubulin and to have potent cytotoxic activity against tumor cells, possibly because of its highly electrophilic epoxide moiety. To test this hypothesis, we synthesized the epoxide-free disorazole C1 and found it retained potent antiproliferative activity against tumor cells, causing prominent G2/M phase arrest and inhibition of in vitro tubulin polymerization. Furthermore, disorazole C1 produced disorganized microtubules at interphase, misaligned chromosomes during mitosis, apoptosis, and premature senescence in the surviving cell populations. Using a tubulin polymerization assay, we found disorazole C1 inhibited purified bovine tubulin polymerization, with an IC50 of 11.8 ± 0.4 μM, and inhibited [3H]vinblastine binding noncompetitively, with a Ki of 4.5 ± 0.6 μM. We also found noncompetitive inhibition of [3H]dolastatin 10 binding by disorazole C1, with a Ki of 10.6 ± 1.5 μM, indicating that disorazole C1 bound tubulin uniquely among known antimitotic agents. Disorazole C1 could be a valuable chemical probe for studying the process of mitotic spindle disruption and its relationship to premature senescence.
Footnotes
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↵1 M. B. Tierno, B. Petrik, D. Nickischer, and P. Johnston, Application Note LC01612000, Thermo Scientific, Pittsburgh, PA. http://www.cellomics.com/content/menu/Compartmental_Analysis_AS/
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This work was supported by the National Institutes of Health [Grants CA078039 and CA097190; SPORE in Head and Neck Cancer]; the Fiske Drug Discovery Fund; and the METACyt Initiative of Indiana University [partially funded through a grant from the Lilly Endowment, Inc.].
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doi:10.1124/jpet.108.147330.
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ABBREVIATIONS: DMSO, dimethyl sulfoxide; TUNEL, terminal deoxynucleotidyl transferase dUTP nick-end labeling; BrdU, 5-bromo-2′-deoxyuridine; JG-03-14, 2,4-dibromo-5-carbethoxyoy-3-(3,4-dimethyoxyphenyl)pyrrole.
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↵ The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
- Received October 10, 2008.
- Accepted December 8, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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