New Natural Epothilones from Sorangium cellulosum, Strains So ce90/B2 and So ce9

The epothilones A and B were first discovered as antifungal and cytotoxic metabolites in the myxobacterium Sorangium cellulosum. Later they were rediscovered as inhibitors of the tubulin system in a target-oriented screening designed for the detection of Taxol mimetics. The epothilones like Taxol and other taxoids stabilize microtubules, leading to arrest of the cell cycle and eventually to apoptosis. Although their chemical structures are quite diverse, both groups of compounds appear to bind at the same or closely related binding sites o­n -tubulin. Among several beneficial properties, most interestingly, the epothilones are highly active against cell lines resistant to Taxol and other anticancer agents. This resistance is commonly based o­n the induction of the P-glycoprotein drug-transport system and in case of taxoids also o­n mutations in the -tubulin gene. Fortunately the epothilones are not sensitive to both mechanisms, raising high hopes that a new drug can be developed that overcomes the acquired resistance in cancer chemotherapy.

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