Flexible long-chain substituted quinoxalines as G-quadruplex binders exert antitumor effects via cGAS-STING immunomodulatory pathway

Abstract

cGAS-STING signaling is a critical mechanism responsible for detecting cytosolic DNA, among a variety of pathways activating innate immunity, making it as an important target for cancer immunotherapy. G-quadruplexes (G4s) frequently forming in telomeres and promoters are able to regulate biological processes. Many compounds targeting G4s are reported with the capability of triggering DNA damage, while leakage of damaged DNA to cytoplasm can be the signal to stimulate innate immunity. Nevertheless, whether small molecule G4 ligands can activate cGAS-STING pathway is seldomly discussed. In this study, we designed and synthesized three compounds by decorating our previously reported quinoxaline scaffold with various flexible long side chains. Among them, QL-3 was identified as the most promising ligand with binding and stabilizing properties to G4s in vitro. Moreover, QL-3 triggered DNA damage in 4 T1 cells, resulting in the activation of cGAS-STING-TBK1-IRF3 pathway and the subsequent ICD. Finally, QL-3 was proved to be a potent anticancer reagent in BALB/c mice implanted with 4 T1 cells, with the immunomodulatory effects on T cells and cytokines displayed. In summary, this study offered a new strategy for developing G4 ligands for tumor immunotherapy, especially through cGAS-STING pathway.

Keywords: G-quadruplex; Quinoxaline; cGAS-STING.