A Comparative Study on High Selectivities of Human Telomeric Dimeric G-Quadruplexes by Dimeric G-Quadruplex Binders

Area of Science:

• Medicinal Chemistry
• Biochemistry
• Molecular Biology

Background:

• G-quadruplexes (G4s) are non-canonical DNA structures implicated in telomere maintenance and cancer.
• Developing selective G4 binders is crucial for therapeutic applications, particularly targeting dimeric G-quadruplexes (G2T1) in human telomeric regions.

Purpose of the Study:

• To synthesize and characterize novel polyether-tethered bisquinolinium dimers as potential G-quadruplex binders.
• To investigate the binding affinities, selectivities, and thermal stabilization effects of these dimers on various G-quadruplex structures, especially antiparallel G2T1.
• To evaluate the anticancer and telomerase inhibitory activities of the most promising compounds.

Main Methods:

• Synthesis of three new polyether-tethered bisquinolinium dimers (compounds 3a-c).
• Spectroscopic and biophysical assays to determine binding affinities and selectivities towards monomeric and dimeric G-quadruplexes (G1, c-kit1, c-kit2, c-myc, and G2T1).
• Thermal melting assays (ΔTm) to assess DNA stabilization.
• In vitro telomerase inhibition assays and cell-based anticancer activity assays against HeLa and MCF-7 cell lines.

Main Results:

• Compound 3b, featuring a medium-length polyether linker, exhibited 30-425-fold higher binding affinity and selectivity for antiparallel G2T1 over monomeric G-quadruplexes.
• Compound 3b demonstrated significant thermal stabilization of G2T1 (ΔTm >28.1°C), outperforming other reported multimeric G-quadruplex binders.
• The dimeric compounds bind via end-stacking to adjacent G-quadruplex units in G2T1, showing selectivity for antiparallel over mixed-type G2T1.
• Compound 3b displayed strong telomerase inhibition and potent anticancer activity against tested cell lines.

Conclusions:

• Polyether linkers and bisquinolinium moieties play a critical role in modulating the binding affinity, selectivity, and thermal stabilization of dimeric G-quadruplex binders.
• Compound 3b is a highly selective binder of antiparallel G2T1, offering significant thermal stabilization and demonstrating promising anticancer and telomerase inhibitory potential.
• These findings underscore the therapeutic potential of tailored bisquinolinium dimers for targeting G-quadruplex structures in cancer therapy.