Design, synthesis and anticancer activity of superoxide anion-releasing beta-galactoside prodrugs

Four novel β-galactoside prodrugs were designed and synthesized from anthraquinones HAQ-OH and AQ-OH in an attempt to use the prodrugs to selectively release superoxide anion (O₂⁻) in cancer cells and to achieve selected anticancer activity by utilizing the Warburg effect and the elevated level of β-galactosidase in certain cancer cells. Cellular assays showed that the prodrugs Gal-HAQ and Gal-AQ selectively inhibited the proliferation and induced apoptosis of ovarian cancer OVCAR-3 cells overexpressing β-galactosidase. Using O₂⁻ fluorescent probe, it was found that in OVCAR-3 cells Gal-HAQ and Gal-AQ could time-dependently release O₂⁻, which was essential for their anticancer activity. Furthermore, it was found that Gal-HAQ and Gal-AQ were effective senolytics toward senescent cells overexpressing β-galactosidase without affecting the viability of corresponding non-senescent cells, further confirming the β-galactosidase-dependent cytotoxicity of the prodrugs. In conclusion, Gal-HAQ and Gal-AQ, which release O₂⁻ in response to β-galactosidase, are expected to serve as candidate prodrugs targeting cancer cells.