PhenQE8, a Novel Ligand of the Human Telomeric Quadruplex

Abstract

A novel quadruplex ligand based on 1,10-phenanthroline and incorporating two guanyl hydrazone functionalities, PhenQE8, is reported herein. Synthetic access was gained in a two-step procedure with an overall yield of 61%. X-ray diffraction studies revealed that PhenQE8 can adopt an extended conformation that may be optimal to favor recognition of quadruplex DNA. DNA interactions with polymorphic G-quadruplex telomeric structures were studied by different techniques, such as Fluorescence resonance energy transfer (FRET) DNA melting assays, circular dichroism and equilibrium dialysis. Our results reveal that the novel ligand PhenQE8 can efficiently recognize the hybrid quadruplex structures of the human telomeric DNA, with high binding affinity and quadruplex/duplex selectivity. Moreover, the compound shows significant cytotoxic activity against a selected panel of cultured tumor cells (PC-3, HeLa and MCF-7), whereas its cytotoxicity is considerably lower in healthy human cells (HFF-1 and RPWE-1).

DNA Interactions and Biological Activity of 2,9-Disubstituted 1,10-Phenanthroline Thiosemicarbazone-Based Ligands and a 4-Phenylthiazole Derivative

“…All reagents and solvents were acquired from commercial sources in high purity form Merck (Madrid, Spain) BLD Pharm (Reinbek, Germany), Carlo Erba Reagents (Sabadell, Spain), PanReac AppliChem-ITW Reagents (Barcelona, Spain), Fisher (Alcobendas, Spain) Scharlab (Barcelona, Spain), Acros Organics (Alcobendas, Spain) and Thermo Scientific Chemicals (Alcobendas, Spain) and used as received. 1,10-phenanthroline-2,9-carbaldehyde was synthesized following a reported procedure [29]. Analytical TLC was performed on precoated aluminum silica gel sheets (Merck, Madrid, Spain, 60 F 254 0.25 mm).…”

“…IR: v (cm −1 ): 3245, 2839, 1540, 1439, 1267, 1147, 1037. FRET DNA melting assays were conducted following standard reported procedures [29]. Briefly, the employed oligonucleotides F21T (5 ′ -FAM-(GGG TTA) 3 GGG-TAMRA-3 ′ ) and F10T (5 ′ -FAM-TAT AGC TA TA/Sp18/TA GCT ATA-TAMRA-3 ′ ) were dissolved in buffer at 0.25 µM concentration and annealed by heating at 90 • C for 5 min, and then immediately cooling to 0 • C, in the case of F21T, or slowly to rt (F10T) during a period of 3 hours.…”

“…CD experiments were performed as previously reported [29]. Unlabeled Tel22 telomeric quadruplex sequence (5 ′ -A(GGGTTA) 3 GGG-3 ′ ) at 4 µM concentration was folded in the same conditions as those employed for FRET-based melting experiments, using the buffering system as for G4 F21T.…”

“…We have recently reported a new G4 ligand derived from the 1,10-phenanthroline heterocycle (Figure 1A), compound PhenQE8 [29], which has proven cytotoxic in several types of tumor cells (PC-3, HeLa and MCF-7), with IC 50 values in the low micromolar concentration range. At the same time, it exhibited lower cytotoxicity in the normal cells evaluated, HFF-1 and RWPE-1, demonstrating a good selectivity potential.…”

Targeting the RNA G-Quadruplex and Protein Interactome for Antiviral Therapy

“…Factors such as limited bioavailability, severe toxicity, and unfavorable pharmacokinetics are still the main obstacles in this field. Notably, an number of new types of G4 ligands, such as 1a-f, 121 PhenQE8, 122 PyDH2, and PhenDH2, 113 have been synthesized based on the above-described molecules. In the future, designing more specific ligands based on sequence specificity to viral G4s will be one goal.…”