Effects of Triethylene Tetraamine on the G-quadruplex Structure in the Human c-myc Promoter

Triethylenetetramine pharmacology and its clinical applications

Triethylenetetramine (TETA), a Cu(II)-selective chelator, is commonly used for the treatment of Wilson's disease. Recently, it has been shown that TETA can be used in the treatment of cancer because it possesses telomerase inhibiting and anti-angiogenesis properties. Although TETA has been used in the treatment of Wilson's disease for decades, a comprehensive review on TETA pharmacology does not exist. TETA is poorly absorbed with a bioavailability of 8 to 30%. It is widely distributed in tissues with relatively high concentrations measured in liver, heart, and kidney. It is mainly metabolized via acetylation, and two major acetylated metabolites exist in human serum and urine. It is mainly excreted in urine as the unchanged parent drug and two acetylated metabolites. It has a relatively short half-life (2 to 4 hours) in humans. The most recent discoveries in TETA pharmacology show that the major pharmacokinetic parameters are not associated with the acetylation phenotype of N-acetyltransferase 2, the traditionally regarded drug acetylation enzyme, and the TETA-metabolizing enzyme is actually spermidine/spermine acetyltransferase. This review also covers the current preclinical and clinical application of TETA. A much needed overview and up-to-date information on TETA pharmacology is provided for clinicians or cancer researchers who intend to embark on cancer clinical trials using TETA or its close structural analogs.

G-quadruplexes: targets in anticancer drug design

G-quadruplexes are special secondary structures adopted in some guanine-rich DNA sequences. As guanine-rich sequences are present in important regions of the eukaryotic genome, such as telomeres and the regulatory regions of many genes, such structures may play important roles in the regulation of biological events in the body. G-quadruplexes have become valid targets for new anticancer drugs in the past few decades. Many leading compounds that target these structures have been reported, and a few of them have entered preclinical or clinical trials. Nonetheless, the selectivity of this kind of antitumor compound has yet to be improved in order to suppress the side effects caused by nonselective binding. As drug design targets, the topology and structural characteristics of quadruplexes, their possible biological roles, and the modes and sites of small-ligand binding to these structures should be understood clearly. Herein we provide a summary of published research that has set out to address the above problem to provide useful information on the design of small ligands that target G-quadruplexes. This review also covers research methodologies that have been developed to study the binding of ligands to G-quadruplexes.

Characterization and antitumor activity of triethylene tetramine, a novel telomerase inhibitor

Triethylene tetramine (TETA) is a novel ligand for G-quadruplex and has been reported to have many kinds of biological activities, including telomerase inhibition, inducing the senescence of tumor cells, etc. In this study, tumor inhibiting activity of TETA and its mechanism were investigated in HeLa cells, MCF-7 cells and mice transplanted with S180 tumor. Results indicated that TETA inhibited telomerase activity involved in decreasing the expression of human telomerase reverse transcriptase (hTERT). We also observed that a low concentration of TETA had limited ability to inhibit the growth of tumor cells in short-term culture, but it could significantly enhance antitumor activity of traditional antitumor drugs in vitro and in vivo.

Triethylene tetramine, a novel ligand of G-quadruplex, induces senescence of MCF-7 cells

Interference with telomerase and telomere maintenance is emerging as an attractive target for antitumor therapies. Ligands stabilizing G-quadruplexes have the potential to interfere with telomere replication by blocking the elongation of telomeres in tumors. Here, we report that long-term treatment with triethylene tetramine (TETA), at 50 or 100 microM, induced marked cellular senescence phenotypes accompanied by increased time of population doubling of MCF-7 cells. Cyclin-dependent kinase inhibitors, including p53 and p21, were also upregulated in TETA-treated MCF-7 cells. TETA is therefore as novel ligand of G-quadruplex and can induce tumor senescence; it is a promising material for tumor treatment.