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

Abstract

AbstractGenome-wide analysis showed that putative G-quadruplex DNA structures are prevalent in the human genome. The presence of G-quadruplex structure in the telomere and promoter region of certain oncogenes inspired people to use G-quadruplex ligand as anti-cancer agents. G-quadruplex structures, stabilized by ligand at telomere are resolved by telomerase making the cancer cells resistant to G-quadruplex ligand. So, identification of a new G-quadruplex ligand having anti-telomerase activity would be a promising strategy for cancer therapy as about 85% of human cancers are telomerase positive. A set of the drug-like compounds were screened from the ZINC database randomly and 2284 ligands were chosen following Lipinski’s rule of five that were docked with five different G-quadruplex DNA sequences in idock. We screened 43 potential G-quadruplex binders using Z-score as a normalization scoring function. The compound (ZINC ID-05220992) gave the best score (average idock = −10.17 kcal/mol, average normalized idock = −3.42). We performed G4 FID assay, CD analysis to understand its binding with three different G-quadruplex DNA sequences, and checked its anti-telomerase activity in A549 cells using TRAP assay. We observed that this compound had an intrinsic fluorescence, capability to stain live cells with a blue fluorescence, and a specific affinity to only 22AG out of three different G-quadruplex DNA sequences under study. It showed cytotoxicity, good permeability to live cells, and a significant reduction of telomerase activity in human A549 cells at a very low dose. So, this compound has strong potential to be an anti-cancer drug.Graphical AbstractHighlightsA set of compounds were screened randomly by a High throughput method and Lipinski’s rule of five from ZINC database to identify potential G4-binders.The compound (ZINC ID-05220992) was screened after docking with five G-quadruplex DNAIt binds G-quadruplex DNA 22AG as detected by TO displacement and CD spectroscopy.It inhibits telomerase activity in A549 cells and also cytotoxic to this cell.It penetrates live A549 cell in culture and stains it with blue fluorescence