Selective binding of a bioactive porphyrin-based photosensitizer to the G-quadruplex from the KRAS oncogene promoter

Abstract Background The G-quadruplex-forming sequence within the KRAS proto-oncogene P1 promoter is a promising target for anticancer therapy. Porphyrin derivatives are among the most rewarding G-quadruplex binders. They can also behave as photosensitizers. Methods Three water-soluble, positively charged porphyrin-like compounds were synthesized and tested for their interaction with the KRAS G-quadruplex by circular dichroism, fluorescence, and molecular docking calculations. For a comparison of ligands binding affinity and selectivity, TMPyP4 was taken as a reference. Results One out of the three tested compounds proved biological activity and selectivity for G-quadruplex over duplex DNA. It also showed to discriminate between different G-quadruplex topologies, with a preference for the parallel over antiparallel conformation. Molecular docking studies suggested a preferential binding to the 3′-end of the KRAS G-quadruplex driven through π-π stacking interactions. Biological assays also revealed a good photodynamic-induced cytotoxicity on HeLa cells. Conclusions The reported results show that these porphyrin-like compounds could actually give the basis for the development of G-quadruplex ligands with effective photodynamic-induced cytotoxicity on cancer cells. General significance The possibility of obtaining photosensitizers with improved physico-chemical features and able to selectively target G-quadruplexes is a very interesting perspective to develop new therapeutic agents.