Design, synthesis, and biological evaluation of N1-(2-(adamantan-1-yl)-1H-indol-5-yl)-N2-(substituent)-1,2-dicarboxamides as anticancer agents targeting Nur77-mediated endoplasmic reticulum stress.

Targeting endoplasmic reticulum (ER) stress-induced apoptosis has attracted considerable research interest in anti-cancer drug development. Nur77 is a potential therapeutic target in many cancers and several Nur77 modulators have recently been identified as effective anticancer agents by activating ER stress. As an ongoing work, this study reports a new series of novel N1-(2-(adamantan-1-yl)-1H-indol-5-yl)-N2-(substituent)-1,2-dicarboxamides as potent Nur77 modulators that cause ER stress-induced apoptosis. Among this new series, most compounds show improved cytotoxicity against liver cancer (HepG2 and Huh7) and breast cancer (MCF-7 and MDA-MB-231) cell lines. The representative analog 15h dramatically induces Nur77 expression and cell apoptosis, showing excellent growth inhibition of HepG2 and MCF-7 cells (IC50 < 5.0 μM). Mechanistically, 15h binds (KD = 0.477 μM) and activates Nur77-mediated ER stress through the PERK-ATF4 and IRE1 signaling pathways, thereby inducing cell apoptosis. In vivo, 15h treatment strongly suppresses HepG2 xenograft tumor growth (tumor shrink by 54.06 %). In summary, we synthesize a series of novel indole derivatives, among which 15h has significantly improved pharmacological activity against various cancer cells. We further identify 15h as a novel ligand of Nur77, which may serve a therapeutic lead for developing new cancer therapy.