Alkyne-substituted diminazene as G-quadruplex binders with anticancer activities

Abstract

G-quadruplex ligands have been touted as potential anticancer agents, however, none of the reported G-quadruplex-interactive small molecules have gone past phase II clinical trials. Recently it was revealed that diminazene (berenil, DMZ) actually binds to G-quadruplexes 1000 times better than DNA duplexes, with dissociation constants approaching 1 nM. DMZ however does not have strong anticancer activities. In this paper, using a panel of biophysical tools, including NMR, FRET melting assay and FRET competition assay, we discovered that monoamidine analogues of DMZ bearing alkyne substitutes selectively bind to G-quadruplexes. The lead DMZ analogues were shown to be able to target c-MYC G-quadruplex both in vitro and in vivo. Alkyne DMZ analogues display respectable anticancer activities (single digit micromolar GI50) against ovarian (OVCAR-3), prostate (PC-3) and triple negative breast (MDA-MB-231) cancer cell lines and represent interesting new leads to develop anticancer agents.

Ultrafast Dynamics of a Triazene: Excited-State Pathways and the Impact of Binding to the Minor Groove of DNA and Further Biomolecular Systems

“…Berenil shows a high binding affinity to enzymes like βtrypsin 7,8 or diamine oxidase, 9 it is an efficient minor-groove binder of AT-rich DNA, 1,10−20 and it also strongly binds to Gquadruplex DNA. 21,22 A characteristic blue fluorescence emitted by berenil after UV excitation is observable when it is added to cell cultures that are in the stationary or lag phase of a growth cycle, yet it is absent when berenil is added to cells in the log phase. 1,23 Until now, no explanation could be found for this exceptional behavior, and, in general, emission from berenil is not reported but the molecule is rather described as nonfluorescent.…”

“…For instance, berenil is the most widely used drug for treating sleeping sickness in animals, and it also acts as babesiacide. − However, little is known about the underlying mechanism and how the properties of berenil change upon interaction with biomolecules. Berenil shows a high binding affinity to enzymes like β-trypsin , or diamine oxidase, it is an efficient minor-groove binder of AT-rich DNA, ,− and it also strongly binds to G-quadruplex DNA. , A characteristic blue fluorescence emitted by berenil after UV excitation is observable when it is added to cell cultures that are in the stationary or lag phase of a growth cycle, yet it is absent when berenil is added to cells in the log phase. , Until now, no explanation could be found for this exceptional behavior, and, in general, emission from berenil is not reported but the molecule is rather described as nonfluorescent. , While these observations suggest that the deactivation channel of berenil after photoexcitation is sensitive to the surrounding, the virtual absence of fluorescence hints to very fast excited-state dynamics comprising photoisomerization and internal conversion.…”

High throughput screening of a new fluorescent G-quadruplex ligand having telomerase inhibitory activity in human A549 cells

“…To observe the cellular uptake of this compound by the live-cell A549 under culture condition with and without using a fixative, we incubated the A549 cells in presence of a very low concentration (20 nM) of C-992 in PBS for 30 min at 37 °C as per our previous report [24,35,36]. Then the cell images were captured under bright field mode (data not Several reports showed that the G-quadruplex ligand can inhibit telomerase activity [35][36][37][38][39][40].…”

Side-Chain-Dependent Binding of bis-Naphthalimide Self-Assembled Nanoparticles to G-Quadruplex DNA for Potential Anticancer Therapy

“…Guanine-rich quadruplex DNA (G4-DNA) is usually formed in human telomeres and oncogene promoter regions by π–π stacking of the G-quartets (i.e., the Hoogsteen hydrogen-bonded G-quartet). , The formation of G4 at the ends of the telomeres can inhibit telomere elongation, leading to inhibition of telomerase activity. − Stabilization of telomeric G4 in cancer cells often leads to apoptosis. − Recently, there has been an increasing interest in the development of G4-DNA-interactive small organic molecules because they can interact via noncovalent interactions with the nucleic acids and, in principle, discriminate between different tertiary DNA structures. − For instance, the development of organic small molecules containing large planar aromatic conjugates (anthracene, squaraine, pyrene, perylene, perylene diimides, (PDI), naphthalene monoimide (i.e., naphthalimide (NI)), and naphthalene diimides (NDI)) have attracted considerable interest due to their potential application as supramolecular DNA-binders. − Development of small molecules that become self-assembled ligands (SALs) prior to binding to a biomolecule is a good approach to biomolecular surface recognition. − The presence of an extended aromatic ring system is a common feature of SALs, which interact primarily via π–π stacking with the G-tetrads and stabilize the G4 structure by inserting their planar aromatic scaffolds between two adjacent base pairs of nucleic acids. , Generally, NI undergoes spontaneous aggregation in aqueous solution due to the presence of the hydrophobic aromatic ring system and produces well-defined self-assembled structures that have optical properties, such as aggregation-caused quenching (ACQ) and aggregation-induced emission (AIE)). Self-assembly and AIE characteristics of NI have been demonstrated; − however, it is still a challenge to develop small organic molecules that can interact with biological targets with high affinity due to the dynamic nature of the biological macromolecules. − …”