Ellagic Acid Enhances RSL3-Induced Ferroptosis by Inhibiting the Nrf2/HO-1 Signaling Pathway in Pancreatic Ductal Adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) exhibits profound therapeutic resistance due to redox adaptation, particularly through Nrf2/HO-1 pathway activation. Ferroptosis induction via GPX4 inhibitors (e.g., RSL3) is promising but limited by adaptive antioxidant responses. Ellagic acid (EA), a natural polyphenol, may overcome this resistance, yet its role in modulating ferroptosis remains unexplored. In vitro studies used KRAS-mutant and KRAS wild-type PDAC cell lines (PANC-1, BxPC-3) treated with EA, RSL3, or both. Ferroptosis markers (iron, lipid ROS, MDA, GPX4), viability assays, and pathway analyses (Keap1/Nrf2/HO-1, p38 MAPK) were evaluated. In vivo, antitumor efficacy was assessed in PANC-1 xenografts. EA synergized with RSL3, reducing viability in PDAC cells (p < 0.001) and suppressing tumor growth in vivo (p < 0.001). Combination therapy amplified ferroptotic markers as increased intracellular iron, MDA, and lipid ROS, versus RSL3 alone, while GPX4 expression decreased. Ferroptosis specificity was confirmed via Fer-1 rescue. Mechanistically, EA activated p38 MAPK, suppressing Nrf2 nuclear translocation and HO-1 expression. Keap1 upregulation further enhanced Nrf2 degradation. In vivo, EA + RSL3 downregulated Nrf2/HO-1 and elevated phospho-p38 in tumors along with the induction of ferroptosis. EA potentiates RSL3-induced ferroptosis in PDAC by disrupting the p38/Nrf2/HO-1 axis and elevating Keap1. This natural compound-based strategy overcomes redox-driven resistance, offering a translatable approach for PDAC models.