Disorazoles comprise a family of 29 macrocyclic polyketides isolated from the fermentation broth of the myxobacterium Soran- gium cellulosum. The major fermentation product, disorazole A 1, 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 C 1 and found it retained potent antiproliferative activity against tumor cells, causing prominent G 2/M phase arrest and inhibition of in vitro tubulin polymerization. Furthermore, disorazole C 1 produced disorganized micro- tubules at interphase, misaligned chromosomes during mitosis, apoptosis, and premature senescence in the surviving cell populations. Using a tubulin polymerization assay, we found dis- orazole C 1 inhibited purified bovine tubulin polymerization, with an IC 50 of 11.8 ± 0.4 μM, and inhibited [ 3H]vinblastine binding noncompetitively, with a K i of 4.5 ± 0.6 μM. We also found noncompetitive inhibition of [ 3H]dolastatin 10 binding by disorazole C 1, with a K i of 10.6 ± 1.5 μM, indicating that disorazole C 1 bound tubulin uniquely among known antimitotic agents. Disorazole C 1 could be a valuable chemical probe for studying the process of mitotic spindle disruption and its relationship to premature senescence.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Pharmacology and Experimental Therapeutics|
|State||Published - Mar 2009|
ASJC Scopus subject areas
- Molecular Medicine