Abstract Background: Endometrial cancer (ECa), the most common malignancy of the female reproductive tract, has rising incidence and mortality, highlighting the need for better treatments. Targeting leukemia inhibitory factor receptor (LIFR) with EC359 shows promise by reducing viability and invasion in both Type I and II ECa. Since LIFR signaling is linked to ferroptosis, an iron-dependent cell death, this study explores whether EC359 induces ferroptosis and enhances chemotherapy, offering a novel therapeutic strategy for advanced ECa. Methods: Chemotherapy-resistant ECa cell lines were established through prolonged exposure to chemotherapeutic agents and validated by RNA sequencing to confirm resistance-associated transcriptional profiles. The antitumor effects of EC359 were assessed in multiple established and patient-derived primary ECa cell models through colony formation assays, MTT-based cell viability assays, and apoptosis analysis. Mechanistic studies were conducted using Western blotting, RT-qPCR, transmission electron microscopy (TEM), and flow cytometry to evaluate ferroptosis-related markers and cellular changes. For preclinical validation, patient-derived organoids (PDO) and xenograft (PDX) models of ECa were employed to determine the therapeutic efficacy of EC359 in combination in vivo. Results: RNA-seq analysis of taxol-resistant ECa cells revealed upregulation of pathways associated with cell proliferation, stemness, and LIFR signaling, along with downregulation of apoptotic pathways. EC359 significantly reduced cell viability in taxol-resistant advanced ECa models. Notably, the cytotoxic effect of EC359 was markedly attenuated when ferroptosis was pharmacologically inhibited using Ferrostatin-1, indicating that ferroptosis is a key mechanism of EC359-induced cell death. Mechanistic studies demonstrated that EC359 suppresses the glutathione antioxidant defense system, thereby promoting ferroptosis. Consistent with this, supplementation with extracellular cystine restored cell viability following EC359 treatment. Moreover, EC359 markedly reduced the expression of key anti-ferroptosis proteins. Flow cytometry confirmed increased lipid peroxidation in EC359-treated cells, while TEM studies revealed characteristic mitochondrial damage associated with ferroptosis. Importantly, EC359 combined with chemotherapy significantly decreased the viability of PDOs and robustly inhibited tumor progression in PDX models of advanced ECa. Conclusion: Our studies suggest that EC359 induces ferroptosis by disrupting antioxidant defenses and synergizes with chemotherapy and that EC359 serve as a promising strategy to overcome chemoresistance in advanced ECa. Citation Format: Emily Jean Aller, Baskaran Subramani, Xue Yang, Paulina Ramirez, Bindu Santhamma, Hareesh B. Nair, Edward Kost, Ratna K. Vadlamudi, Suryavathi Viswanadhapalli. LIFR inhibition with EC359 triggers ferroptosis to overcome chemoresistance in endometrial cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 5679.
Aller et al. (Fri,) studied this question.