Discovery of a potent Guanidine derivative that selectively binds and stabilizes the human BCL-2 G-quadruplex DNA and downregulates the transcription.

G-quadruplex also known as G4 (GQ) structures, are a non-canonical kind of DNA or RNA secondary structure that may develop inside guanine-rich nucleic acid sequences. They may be found in a variety of locations in the human genome, such as gene promoters, 5' untranslated region, and telomeres, among others. Because of their significance in biology, G4 structures are recognized as promising pharmacological targets, particularly for therapeutics against cancer. This has led to the discovery of small molecules that can stabilize G4 structures. Small molecules that interact with quadruplexes offer a wide range of potential applications, including not just as medications but also as sensors for quadruplexes structures. The BCL-2 is a proto-oncogene that often gets mutated in lethal cancer and could be an interesting target for developing an anti-cancer drug. In the present study, we have employed various biophysical techniques such as fluorescence, CD, Isothermal calorimetry, gel retardation, and PCR stop assay, indicating that Guanidine derivatives GD-1 and GD-2 selectively interact with high affinity with BCL-2 GQ over other G-quadruplex DNA and duplex DNA. The most promising small molecule GD-1 increases the thermostability of the BCL-2 GQ structure by 12°C. Our biological experiments such as ROS generation, qRT-PCR, western blot, TFP based reporter assay, show that the GD-1 ligand causes a synthetic lethal interaction by suppressing the expression of BCL-2 genes via interaction and stabilization of its promoter GQ strucure in HeLa cells and act as a potential anti-cancer agent.