Synthesis, Interactions With DNAs And Biological Activity Of Terpyridine Derivatives

Two novel terpyridine derivatives with a coumarin group (1) and a benzothiazole group (2) have been synthesized, and the interactions of the target compound 1 with human telomeric (h-telo and i-motif) quadruplexes and oncogene promoter (c-kit2 and o-myc) G-quadruplex DNAs have been investigated by a series of experimental techniques. At the same time, its cytotoxicity, effect on cell cycle, and inhibitory activities against telemerase and Topoisomerase I are also evaluated. The results are as follows:1. In the FRET-melting assay, while the concentration of the target compound 1 increased to 3 μM, the melting temperature change values (△Tm) of the h-telo, c-kit2, and c-myc G-quadruplex DNAs were 15.0,13.6, and 9.3 ℃, respectively, suggesting that the target compound 1 could stabilize these G-quadruplex DNAs. And the PCR-Stop assay displayed that their products of PCR amplification could be inhibited by the target compound 1 with the concentration at 10-5M. The results of UV-melting assay indicated that the target compound 1 could stabilize the i-motif DNA to some extent, whereas it did not affect the stability of the ct-DNA.2. In the competitive FRET-melting assay, the melting temperature change values (△Tm) of the c-kit2 and o-myc G-quadruplex DNAs did not change obviously at 25-fold excess of ds26, indicating that the target compound 1 was able to bind to them preferentially. But the melting temperature change value of c-kit2 minished largely in the presence of 50-fold excess of ds26, demonstrating that the selective ability to c-kit2 was reduced as increasing the concentration of target compound 1. While the melting temperature change value (△Tm) decreased from 9.6 to 4.6℃ at 10 times excess of ds26, it exhibited lower selectivity to the h-telo G-quadruplex DNA. In the FID assay, the target compound 1 could not displace effectively TO from G-quadruplex DNAs, which may be due to their different binding sites at G-quadruplexes.3. UV-vis titration experiment showed that the target compound 1 could interact strongly with h-telo, c-myc, c-kit2, and i-motif quadruplexes and ct-DNA, and their binding constants were about 105M-1. Simultaneously, the CD assay indicated that the target compound 1 could not make the random h-telo DNA form a G-quadruplex DNA structure in the absence of cations, while it might promote the formation of the antiparallel conformation of the h-telo G-quadruplex DNA from the hybrid structure gradually in the presence of 100 mM K+. What’s more, the target compound 1 disturbed slightly the structures of c-myc and c-kit2 G-quadruplex DNAs, whereas it almost did not influence the conformation of i-motif DNA.4. The TRAP assay confirmed that the target compound 1 could inhibit the activity of telomerase at the concentration of 10-5M and was a potential telomerase inhibitor.5. The gel mobility shift assay exhibited that the pBR322 DNA was not cleaved by target compound 1. Furthermore, the agarose gel electrophoresis assay revealed that the target compound 1 displayed a significant inhibition of Topo I-mediated relaxation of plasmid pBR322 DNA in a concentration-dependent mode. And the introduction of coumarin group and the coordination of Pt(II) improved the Topo I inhibitory activity of terpyridine derivatives.6. In the MTT assay, the target compound 1 could inhibit the proliferation of HepG2 and MCF7 cell lines with the increasing amounts of the compound. And the IC50 values of the target compound 1 were found to be 3.66 and 1.54 μM for HepG2 cells and MCF7 cells, respectively. Moreover, the cell cycle test displayed that the target compound 1 could arrest the cell cycle in S phase in the case of HepG2 cells, while it made cell cycle of MCF7 cells arrest in the G0/G1 and S phases.