In the course of our search for hypoxia-selective growth inhibitors against cancer cells, a sesquiterpene phenol, dictyoceratin-C (1), was isolated from the Indonesian marine sponge of Dactylospongia elegans under the guidance of the constructed bioassay. Dictyoceratin-C (1) inhibited proliferation of human prostate cancer DU145 cells selectively under hypoxic condition in a dose-dependent manner at the concentrations ranging from 1.0 to 10 μM. The subsequent structure-activity relationship study using nine sesquiterpene phenol/quinones (2-10), which were isolated from marine sponge, was executed. We found that smenospondiol (2) also exhibited the similar hypoxia-selective growth inhibitory activity against DU145 cells, and the para-hydroxybenzoyl ester moiety would be important for hypoxia-selective growth inhibitory activity of 1. In addition, the mechanistic analysis of dictyoceratin-C (1) revealed that the 10 μM of 1 inhibited accumulation of Hypoxia-Inducible Factor-1α under hypoxic condition.
Keywords: Cancer; Dactylospongia elegans; Dictyoceratin-C; HIF-1α; Hypoxia; Smenospondiol.
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