1. ¹State Key Laboratory of Oncology in Southern China, Cancer Center, Sun Yat-sen University, Guangzhou, China
2. ²School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China

Correspondence: Dr X-F Zhu or Dr Y-X Zeng, State Key Laboratory of Oncology in Southern China, Cancer Center, Sun Yat-sen University, 651 Dongfeng Road East, Guangzhou 510060, China. E-mail: xfzhu70@public.guangzhou.gd.cn or yxzeng@gzsums.edu.cn; Dr Z-S Huang, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510089, China. E-mail: cedc43@zsu.edu.cn

Received 2 May 2005; Revised 1 August 2005; Accepted 1 August 2005; Published online 19 September 2005.

Abstract

Agents stabilizing G-quadruplexes have the potential to interfere with telomere replication by blocking the elongation step catalysed by telomerase or telomerase-independent mechanism and could therefore act as antitumor agents. In this study, we found that quindoline derivatives interacted preferentially with intramolecular G-quadruplex structures and were novel potent telomerase inhibitors. Treatment with quindoline derivatives reproducibly inhibited telomerase activity in human leukemia K562 cells and colon cancer SW620 cells. N'-(10H-Indolo [3,2-b] quinolin-11-yl)-N, N-dimethyl-propane-1,3-diamine (SYUIQ-5), (one of quindoline derivatives), when added to K562 and SW620 cell culture at nonacute cytotoxic concentrations, increased time of population doublings of K562 and SW620 cells, induced a marked cessation in cell growth and cellular senescence phenotype after 35 and 18 days, respectively. Growth cessation was accompanied by a shortening of telomere length, and induction of p16, p21 and p27 protein expression. However, another compound SYUIQ-7 with greater IC₅₀ for telomerase had no obvious cellular effect in nonacute cytotoxic concentrations. These results indicate that quindoline derivatives as novel potent G-quadruplex interactive agents induce senescence and telomere shortening in cancer cells and therefore are promising agents for cancer treatment.