Butylidenephthalide Suppresses Human Telomerase Reverse Transcriptase (TERT) in Human Glioblastomas
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Telomerase is widely expressed in most human cancers, but is almost undetectable in normal somatic cells and is therefore a potential drug target. Using the human telomerase promoter platform, the naturally occurring compound butylidenephthalide (BP) was selected for subsequent investigation of antitumor activity in vitro and in vivo.
We treated human glioblastoma cells with BP and found a dose-dependent decrease in human telomerase reverse transcriptase (hTERT) mRNA expression and a concomitant increase in p16 and p21 expression. Because c-Myc and Sp1 are involved in transcriptional regulation of hTERT, the effect of BP on c-Myc and Sp1 expression was examined.
Using electrophoretic mobility shift assays and western blotting, we showed that BP represses hTERT transcriptional activity via downregulation of Sp1 expression. Using the telomerase repeat amplification protocol, an association between BP concentration and suppression of telomerase activity, induction of human glioblastoma senescence, and inhibition of cellular proliferation was identified. This was supported by a mouse xenograft model, in which BP repressed telomerase and inhibited tumor proliferation, resulting in tumor senescence. Overexpression of hTERT restored telomerase activity in human glioblastoma cells and overcame replicative senescence.
These findings suggest that BP inhibits proliferation and induces senescence in human glioblastomas by downregulating hTERT expression and consequently telomerase activity. This is the first study to describe regulation of telomerase activity by BP in human glioblastomas.
KeywordshTERT Expression hTERT mRNA Expression Brain Cancer Cell Butylidenephthalide hTERT Core Promoter
We thank Robert A. Weinberg for the pCI neo-hEST2-HA (Addgene plasmid 1782) construct. Grant: This work was supported by grants from the National Science Council of the Republic of China (96-2320-B-039-044-MY3), from the Center for Neuropsychiatry, China Medical University and Hospital, Taichung, Taiwan, and from China Medical University and Hospital, Taichung, Taiwan (DMR-99-076). This study is supported in part by Taiwan Department of Health Clinical Trial and Research Center of Excellence (DOH99-TD-B-111-004).
- 14.Le S, Zhu JJ, Anthony DC, Greider CW, Black PM. Telomerase activity in human gliomas. Neurosurgery. 1998;42:1120–4; discussion 1124–5.Google Scholar
- 38.Cookson JC, Dai F, Smith V, Heald RA, Laughton CA, Stevens MF, et al. Pharmacodynamics of the G-quadruplex-stabilizing telomerase inhibitor 3,11-difluoro-6,8,13-trimethyl-8H-quino[4,3,2-kl]acridinium methosulfate (RHPS4) in vitro: activity in human tumor cells correlates with telomere length and can be enhanced, or antagonized, with cytotoxic agents. Mol Pharmacol. 2005;68:1551–8.PubMedGoogle Scholar