Attenuation of c-Myc expression in breast cancer by hesperidin-mediated stabilization of its promoter proximal G quadruplex region

Abstract The G-Quadruplex (G4) silencer element (Pu-27), an epigenetic regulator located upstream of the c-Myc promoter, when stabilized and restored to its basal expression, presents a potential avenue for effective anticancer therapy. This study investigates Hesperidin, a citrus flavanone, as a potential breast cancer therapy by targeting the c-Myc G-quadruplex (G4) silencer element, Pu-27. Hesperidin showed strong interaction with Pu-27, indicated by a binding score of -7.241 and the formation of hydrogen bonds with five regions of Pu-27 G4, with a binding free energy of -48.344 kcal/mol. Increasing Hesperidin concentration significantly increased Pu-27 G4 ellipticity and melting temperature, suggesting structural stabilization. Atomic force microscopy revealed higher-order nanostructure formation in Pu-27 G4 with Hesperidin. Functional assays demonstrated reduced Pu-27 primer dimer PCR product and mTFP expression with increasing Hesperidin concentration. Selective cytotoxicity against MDA-MB-231 breast cancer cells, attenuation of clonogenicity and migration, along with downregulation of c-Myc expression both in vitro and in vivo in mice tumor models, further supported Hesperidin's potential as a breast cancer therapeutic. These findings highlight Hesperidin's ability to interact with the c-Myc G4 element, influencing cancer cell behavior, and suggest its promise as a therapeutic agent for breast cancer.