G-quadruplex-Based Artificial Transmembrane Channels Induce Cancer Cell Apoptosis by Perturbing Potassium Ion Homeostasis.

Abstract

Transmembrane ion transport modality has received a widespread attention due to its apoptotic activation toward anticancer cell activities. In this study, G-quadruplex-based potassium-specific transmembrane channels have been developed to facilitate the intracellular K⁺ efflux, which perturbs the cellular ion homeostasis thereby inducing cancer cell apoptosis. Cholesterol-tag, a lipophilic anchor moiety, serves as a rudiment for the G-quadruplex immobilization onto the membrane, while G-quadruplex channel structure as a transport module permits ion binding and migration along the channels. A c-Myc sequence tagged with two-cholesterol is designed as a representative lipophilic G-quadruplex, which forms intramolecular parallel G-quadruplex with three stacks of G-quartets (Ch₂-Para3). Fluorescence transport assay demonstrates Ch₂-Para3 a high transport activity (EC₅₀ = 10.9 × 10^-6 m) and an ion selectivity (K⁺/Na⁺ selectivity ratio of 84). Ch₂-Para3 mediated K⁺ efflux in cancer cells is revealed to purge cancer cells through K⁺ efflux-mediated cell apoptosis, which is confirmed by monitoring the changes in membrane potential of mitochondria, leakage of cytochrome c, reactive oxygen species yield, as well as activation of a family of caspases. The lipophilic G-quadruplex exhibits obvious antitumor activity in vivo without systemic toxicity. This study provides a functional scheme aimed at generating DNA-based selective artificial membrane channels for the purpose of regulating cellular processes and inducing cell apoptosis, which shows a great promising for anticancer therapy in the future.