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Cell Cycle, Cell Death, and Senescence

G-Quadruplex Stabilizer 3,6-Bis(1-Methyl-4-Vinylpyridinium)Carbazole Diiodide Induces Accelerated Senescence and Inhibits Tumorigenic Properties in Cancer Cells

¹ Institute of Biopharmaceutical Sciences, National Yang-Ming University; ² Institute of Atomic and Molecular Sciences, Academia Sinica; ³ Department of Otolaryngology, National Taiwan University Hospital; ⁴ Center for Optoelectronic Biomedicine, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China

Requests for reprints: Jing-Jer Lin, Institute of Biopharmaceutical Science, National Yang-Ming University, Taipei 11221, Taiwan, Republic of China. Phone: 886-2-28267258. E-mail: jjlin{at}ym.edu.tw or Ta-Chau Chang, Institute of Atomic and Molecular Sciences, Academia Sinica, P. O. Box 23-166, Taipei 106, Taiwan, Republic of China. E-mail: tcchang{at}po.iams.sinica.edu.tw

Carbazole derivatives that stabilized G-quadruplex DNA structure formed by human telomeric sequence have been designed and synthesized. Among them, 3,6-bis(1-methyl-4-vinylpyridinium)carbazole diiodide (BMVC) showed an increase in G-quadruplex melting temperature by 13°C and has a potent inhibitory effect on telomerase activity. Treatment of H1299 cancer cells with 0.5 µmol/L BMVC did not cause acute toxicity and affect DNA replication; however, the BMVC-treated cells ceased to divide after a lag period. Hallmarks of senescence, including morphologic changes, detection of senescence-associated β-galactosidase activity, and decreased bromodeoxyuridine incorporation, were detected in BMVC-treated cancer cells. The BMVC-induced senescence phenotype is accompanied by progressive telomere shortening and detection of the DNA damage foci, indicating that BMVC caused telomere uncapping after long-term treatments. Unlike other telomerase inhibitors, the BMVC-treated cancer cells showed a fast telomere shortening rate and a lag period of growth before entering senescence. Interestingly, BMVC also suppressed the tumor-related properties of cancer cells, including cell migration, colony-forming ability, and anchorage-independent growth, indicating that the cellular effects of BMVC were not limited to telomeres. Consistent with the observations from cellular experiments, the tumorigenic potential of cancer cells was also reduced in mouse xenografts after BMVC treatments. Thus, BMVC repressed tumor progression through both telomere-dependent and telomere-independent pathways. (Mol Cancer Res 2008;6(6):955–64)