U07, a novel oridonin derivative, targets polo-like kinase 4 (PLK4) to induce ferroptosis in gastric cancer cells.

This study aimed to systematically investigate the inhibitory effect and potential molecular mechanism of oridonin derivative U07 on gastric cancer cells. By combining in vitro cell experiments and in vivo animal experiments, techniques including Cell Counting Kit-8 (CCK-8) assay, colony formation assay, Annexin V-FITC/Propidium Iodide (Annexin V/PI) double-staining flow cytometry, Western blot, wound healing assay, Transwell invasion assay, fluorescence staining, surface plasmon resonance (SPR), isothermal titration calorimetry (ITC), and molecular docking were used to analyze the impact of U07 on the biological behavior of gastric cancer cells and related molecular pathways. The results showed that U07 exhibited concentration-dependent cytotoxicity against HGC-27 and MKN-45 gastric cancer cells (with IC50 values of 2.5 μM and 2.6 μM, respectively). It could inhibit cell proliferation and induce apoptosis by activating the caspase-3 pathway, while significantly reducing cell migration and invasion abilities. U07 concentration-dependently increased the levels of reactive oxygen species (ROS) and lipid peroxidation, decreased glutathione (GSH) content, and increased malondialdehyde (MDA) content, thereby triggering ferroptosis; this effect could be blocked by the ferroptosis inhibitor Fer-1. Molecular studies confirmed that U07 could specifically bind to PLK4 kinase (KD = 6.2 μM detected by SPR, Kd = 0.65 μM detected by ITC) and inhibit its activity. PLK4 negatively regulates frroptosis pathway by directly binding to and transcriptionally activating Glutathione Peroxidase 4 (GPX4) / ferritin heavy chain 1 (FTH1). By downregulating PLK4, U07 further reduced the expression of ferroptosis marker proteins GPX4 and FTH1, and promoted lipid peroxidation and ROS production; however, overexpression of PLK4 could reverse these effects. In vivo experiments demonstrated that U07 could inhibit tumor growth in a dose-dependent manner, with the high-dose group (6 mg) showing an anti-tumor effect comparable to that of cisplatin, and it could downregulate the expression of PLK4 and GPX4 in tumor tissues. In conclusion, the oridonin derivative U07 exerts anti-gastric cancer effects by inhibiting cell proliferation, inducing apoptosis, and mediating ferroptosis via PLK4, providing a new candidate drug and therapeutic target for gastric cancer treatment.