Abstract 1630: Targeting the LIF/LIFR axis reduces the progression of inflammatory breast cancer by promoting ferroptosis

Abstract Background: Inflammatory breast cancer (IBC) is a rare subtype of breast cancer affecting 2-4% of the U.S. population. With the incidence being quite low, IBC is responsible for 7% of breast cancer related mortality often affecting younger women. The only currently approved options for treatment are surgical resection, chemotherapy, and radiation. Novel therapeutic targets are desperately needed for the generation of new therapeutics. IBC progression has been linked to growth factor and cytokine signaling abnormalities. In previous studies, the cytokine LIF/LIFR signaling axis has been identified as a crucial pathway in the progression of triple negative breast cancer. However, the role of LIF/LIFR in IBC progression remains unknown. The objective of this study is to test the utility of LIFR and test the effectiveness of LIFR inhibitor at treating IBC. Methods: The utility of using LIFR inhibition as a treatment strategy in IBC was tested using cell survival, apoptosis, and colony formation assays using established IBC cell models (SUM149, SUM190PT, and KPL-4). We have reduced LIFR levels by 70% in IBC cells utilizing two different siRNAs that target LIFR. Western blotting, luciferase reporter assays, RT-qPCR, and lipid peroxidation assays were used to establish the mechanism of EC359 mediated growth suppression of IBC. In vivo treatment of cell-derived xenografts (KPL-4) was used to assess the utility of EC359. Results: All three IBC models exhibited detectable expressions of LIF and LIFR. Reduction of LIFR using siRNA decreased cell survival, colony formation, and invasion capacity of IBC cells relative to cells transfected with control siRNAs. Pharmacological inhibition of LIFR with EC359 effectively reduced cell survival and clonogenic capacity of IBC cells in the low nanomolar range. RT-qPCR tests revealed EC359 markedly decreased the expression of LIFR target genes. Western analyses confirmed that EC359 treatment suppressed downstream LIF/LIFR signaling pathways, including STAT3, AKT, and pS6, and promoted apoptosis. Treatment of cells with the ferroptosis inhibitor Ferrostatin 1 negated the capacity of EC359 to induce cell death. The evaluation of lipid peroxidation in cells via flow cytometry, utilizing the oxidation of BODIPY™ reagent, further confirmed EC359 induction of ferroptosis. Mechanistic investigations demonstrated that EC359 predominantly triggered ferroptosis by inhibiting the glutathione antioxidant defense system through the downregulation of SLC7A11 and GPX4 levels. EC359 (5 mg/kg/day) was effective in reducing the growth of the IBC KPL4 xenograft tumors. Immunohistochemical examinations of tumors validated reduced cell proliferation as assessed by Ki67 staining. Conclusion: Collectively, our research suggests that the inhibition of LIFR promotes ferroptosis-mediated cell death in IBC, and LIFR inhibitors represent a novel therapeutic option for IBC. Citation Format: Bianca A. Romo, Zenaida Fuentes, Lois Randolph, Megharani Mahajan, Emily J. Aller, Behnam Ebrahimi, Bindu Santhamma, Hareesh B. Nair, Christoforos Thomas, Ratna K. Vadlamudi, Suryavathi Viswanadhapalli. Targeting the LIF/LIFR axis reduces the progression of inflammatory breast cancer by promoting ferroptosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1630.