Discovery of guaianolide-eudesmanolide dimers as antihepatoma agents by targeting NEURL1B to disrupt the DLL1/Notch signaling pathway.

Given the high incidence of hepatocellular carcinoma (HCC) and its limited therapeutic options, and building on our previous work on anti-HCC sesquiterpenoid dimers, a series of natural product-like guaianolide-eudesmanolide dimers were designed and synthesized as potential anti-HCC agents in this study. Among them, compound 1 showed significantly antihepatoma effects on HepG2, Huh-7, and SK-Hep-1 cells with IC50 values of 5.6, 4.8, and 4.6 μM, respectively; induced cell cycle arrest and apoptosis; and inhibited the migration of HCC cells. Bioinformatic analysis and experimental validation indicated that compound 1 directly targeted NEURL1B, which was further established as a critical regulator of HCC proliferation and migration. Mechanistically, compound 1 bound to Arg422 within the NHR2 domain of NEURL1B, triggering its autoubiquitination and degradation, which stabilized DLL1 by suppressing its ubiquitination and ultimately attenuated the Notch signaling pathway. In vivo experiments showed that compound 1 (60 mg/kg) inhibited tumor weight up to 69% in SK-Hep-1 xenograft nude mice, which was comparable to that of sorafenib (67%) at the same dose. This study revealed that the previously unrecognized oncogenic role of NEURL1B acted as upstream of DLL1 in HCC, and suggested that compound 1 might be an antihepatoma candidate that inhibited Notch signaling by disrupting the NEURL1B-DLL1 interaction.