A novobiocin derivative, XN4, triggers ferroptosis in gastric cancer cells via the activation of NOX4

CONTEXT: A novobiocin derivative, XN4, has been shown to promote cell apoptosis in chronic myeloid leukaemia. OBJECTIVE: This study explores the mechanism by which XN4 promotes ferroptosis of gastric cancer (GC) cells. MATERIALS AND METHODS: Human GC SGC-7901 and BGC-823 cells were treated with different XN4 concentrations (0, 0.1, 0.5, 1.0, 5.0, and 10.0 μmol/L) to evaluate effects of XN4. Additionally, cells were pre-treated for 24 h with si-NOX4, for 1 h with the iron chelator deferoxamine mesylate (DFO) or for 1 h with the lipid peroxidation inhibitor liproxstatin-1 before being treated with XN4 to analyse the mechanism of XN4. RESULTS: XN4 increased cell death (IC(50) values of XN4 on SGC-7901 and BGC-823 cells: 1.592 ± 0.14 μmol/L and 2.022 ± 0.19 μmol/L) and Fe(2+) levels in SGC-7901 and BGC-823 cells. These effects of 2.0 μmol/L XN4 were abolished by 100 μmol/L DFO treatment. XN4 enhanced transferrin and transferrin receptor expression to induce Fe(2+) accumulation. XN4 decreased mitochondrial membrane potentials in GC cells, similar to erastin. Additionally, XN4 increased MDA, hydrogen peroxide, and ROS levels, but diminished total glutathione levels. Liproxstatin-1 (200 nmol/L) nullified the effects of XN4 (2.0 μmol/L) on MDA levels and cell death. Moreover, GPX4 levels decreased, but NOX4 and ferroptosis-related protein PTGS2 levels increased in GC cells following XN4 treatment, which was nullified by NOX4 knockdown. DISCUSSION AND CONCLUSIONS: The pro-ferroptotic role of XN4 in GC might enable it to become a promising drug for GC treatment in the future despite the need for extensive research.