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Issue 63, 2014
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Selective G-quadruplex stabilizers: Schiff-base metal complexes with anticancer activity

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The affinity of three square-planar nickel(II) (1), copper(II) (2) and zinc(II) (3) Schiff-base complexes for wild-type human telomeric (h-Telo) and protooncogene c-myc G-quadruplex (G4) DNA was investigated by UV-visible absorption spectroscopy and circular dichroism. DNA-binding constants (Kb) were determined by spectrophotometric titrations for both G4-DNA and B-DNA. The results obtained point out that the three metal complexes selectively bind G4-DNA with higher affinity, up to two orders of magnitude, with respect to B-DNA. The nickel(II) complex 1 was found to be the most effective G4-DNA stabilizer and the Kb values decrease in the order 1 > 23. Innovative computational investigations, consisting of molecular dynamics (MD) simulations followed by density functional theory/molecular mechanics (DFT/MM) calculations, provide atomistic support for the interpretation of the binding mechanism to G4-DNA by end stacking and also of the experimental affinity order. Interestingly, 1 is able to induce G4-DNA formation of h-Telo sequences, also in the absence of K+ cations. This last result is nicely confirmed and highlighted by polymerase chain reaction (PCR) stop assays, which show the ability of the title compounds to induce and stabilize G4 structures inhibiting the amplification of PCR products. Finally, compounds 1–3 showed concentration and time-dependent cytotoxicity towards HeLa and MCF-7 human cancer cell lines, inducing significant effects on cell cycle distribution with G2/M arrest in HeLa cells and G0/G1 arrest in MCF-7 cells. Overall, the PCR inhibition and anticancer activity of the three compounds decreases in the same order 1 > 23, in excellent correlation with the G4-DNA-binding affinity, implying that G4-DNA is the biotarget for their biological activity.

Graphical abstract: Selective G-quadruplex stabilizers: Schiff-base metal complexes with anticancer activity

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The article was received on 05 Jun 2014, accepted on 15 Jul 2014 and first published on 16 Jul 2014

Article type: Paper
DOI: 10.1039/C4RA05355A
Author version available: Download Author version (PDF)
Citation: RSC Adv., 2014,4, 33245-33256
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    Selective G-quadruplex stabilizers: Schiff-base metal complexes with anticancer activity

    A. Terenzi, R. Bonsignore, A. Spinello, C. Gentile, A. Martorana, C. Ducani, B. Högberg, A. M. Almerico, A. Lauria and G. Barone, RSC Adv., 2014, 4, 33245
    DOI: 10.1039/C4RA05355A

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