Estrone-Based Derivatives Stabilize the c-MYC and c-KIT G-Quadruplex DNA Structures

G-rich sequences are present across the genome and can fold to form dynamic secondary structures, namely, G-quadruplexes (G4). These structures play a pivotal role in regulating numerous biological processes including replication, transcription, and translation. Therefore, targeting these structures using molecular scaffolds is an attractive approach to modulating their functions. Herein, we report the synthesis of three estrone-based derivatives (Est-1, Est-2, and Est-3) with a nonplanar core and a cationic alkyl side chain as G4 stabilizers. CD melting and polymerase stop assay results indicate that these ligands preferentially stabilize parallel c-MYC and c-KIT1 G4s over the other G4s and duplex DNAs. The ligand Est-3 shows cytotoxicity against cancer cell lines and effectively downregulates the c-KIT gene in HepG2 cell lines. Molecular modeling and dynamics studies showed that the ligand prefers stacking over the 5'-quartet of c-MYC G4 using the aromatic ring of the ligand. Overall, the findings of this study demonstrate that even G4 ligands can accommodate nonplanar scaffolds, which opens up new avenues for ligand design.