Inhibitory effects of costunolide on the telomerase activity in human breast carcinoma cells.

Costunolide, a natural sesquiterpene compound, has been known having cytotoxic and chemopreventive effects on various human cancer cells. In the present study, we examined the effects of costunolide on telomerase activity and on the components of telomerase in MCF-7 (wild-type p53) and MDA-MB-231 (mutant p53) cells. We found that costunolide inhibited the growth and telomerase activity of MCF-7 and MDA-MB-231 cells in a concentration- and time-dependent manner. The expression of hTERT mRNA was also inhibited but hTR mRNA was not. In addition, the bindings of transcription factors in hTERT promoters were significantly decreased in both cells by the treatment of costunolide. These results suggest that costunolide inhibited the growth of both MCF-7 and MDA-MB-231 cells and this effect was mediated at least in part by a significant reduction in telomerase activity.