Marine Sponge-Derived Gukulenin A Sensitizes Ovarian Cancer Cells to PARP Inhibition via Ferroptosis Induction

Resistance to PARP inhibitors (PARPi), such as olaparib (OLA), is a major challenge in ovarian cancer treatment. In this study, we investigated the combination effect of PARPi and gukulenin A (GUA), a bis-tropolone tetraterpenoid isolated from the marine sponge Phorbas gukhulensis. We found that GUA at a mildly cytotoxic dose synergistically enhanced OLA-induced cytotoxicity in human ovarian cancer cells. The combination treatment significantly increased reactive oxygen species (ROS) levels and lipid peroxidation, leading to ferroptotic rather than apoptotic cell death. Network pharmacology and gene ontology (GO) enrichment analyses revealed oxidative stress-related pathways as key mediators of this effect. Inhibition of NADPH oxidase (NOX) reversed combination-induced cell death, while ferrostatin-1 (FER-1), a ferroptosis inhibitor, significantly reduced lipid peroxidation and cytotoxicity. Additionally, GUA and OLA treatment suppressed ERK1/2 activation, and ERK overexpression attenuated the combination-induced cell death. Collectively, these findings suggest that marine-derived GUA enhances PARPi efficacy in ovarian cancer cells by inducing ferroptosis through oxidative stress and ERK pathway modulation.