Jujuboside B Induces Ferroptosis and Overcomes Radioresistance Through the <scp>PPARγ</scp> ‐ <scp>ATF3</scp> ‐Gpx4 Signaling Pathway in Non‐Small Cell Lung Cancer

Jujuboside B (JJB) is a saponin extracted from the Ziziphus jujuba var. spinose and has been reported to have anticancer effects. However, the detailed mechanism of its anti-cancer effect in non-small cell lung cancer (NSCLC) remains unclear. New combination therapies may be able to overcome TRAIL resistance. In this study, we found that JJB regulates the activity of PPARγ and investigated whether the combination of JJB and TRAIL had synergistic anti-cancer effects against NSCLC cells. Experimental procedure: We assessed cell death induced by the combination of TRAIL and JJB in NSCLC cells using ATPlite Luminescence, LDH, and caspase activity assays. We also examined endoplasmic reticulum (ER) stress-mediated cell death using the intracellular calcium assay and western blot analysis. The combination of JJB and TRAIL significantly reduced cell viability and increased apoptotic cell death by binding CHOP to the DR4/5 promoter in NSCLC cells. JJB induced ferroptosis by increasing the expression of Nox4 and ATF3 and the levels of malondialdehyde (MDA) and reactive oxygen species (ROS), as well as by reducing the expression of SLC7A11 and Gpx4 and the level of glutathione (GSH) through the activation of ER stress. Consistent with this, N-acetylcysteine (NAC) suppressed ER stress-mediated ferroptosis by reducing the expression of Nox4, ATF3, and cleaved caspase-3 and by increasing the expression of SLC7A11 and Gpx4 in JJB-treated NSCLC cells. In radioresistant NSCLC models, combined treatment with JJB and radiation induced ferroptosis and overcame radioresistance by regulating the epithelial-mesenchymal transition (EMT) phenomenon. Therefore, JJB could be a potential therapeutic strategy in NSCLC.