Abstract 5986: Significance of LIF/LIFR axis in the progression of inflammatory breast cancer

Abstract Background: Inflammatory breast cancer (IBC) is a rare form of locally progressed breast cancer. Even though it is uncommon, IBC accounts for 7% of breast cancer deaths. There is a critical need for novel therapeutic targets to develop new therapeutics. IBC is more common in young women. Altered levels of growth factors, and cytokine signaling are suspected to play a role in the progression of IBC. Leukemia inhibitory factor (LIF) is the most pleiotropic member of the interleukin-6 family of cytokines. LIF and its receptor LIFR have been linked to the progression of many cancers including triple negative breast cancer. We recently developed a first-in-class inhibitor targeting LIFR named EC359. However, the role of the LIF/LIFR axis in IBC progression remains unknown. In this study, we examined the significance of LIFR and the effectiveness of LIFR inhibitor EC359 in treating IBC. Methods: The effect of LIFR inhibitor EC359 on cell survival, colony formation, and apoptosis was evaluated using three well-established IBC model cells (SUM149, SUM190PT, and KPL4). Mechanistic studies were conducted using Western blotting, CRISPR KO, reporter assays, and RT-qPCR. KPL4 cell-based xenografts were used to test the efficacy of EC359 in vivo. Results: Our results using Western blotting confirmed increased expression of LIF and LIFR in IBC cells compared to normal and ER+ breast cancer cells. Treatment with EC359 significantly decreased IBC cell viability, long term colony formation ability with an IC50 of ~10-20 nM. Similarly, knock out of LIFR significantly reduced the progression of IBC model cells in cell viability and colony formation assays. Further EC359 treatment promoted apoptosis of IBC cells. Mechanistic studies confirmed that EC359 treatment substantially reduced LIF/LIFR downstream signaling including STAT3, AKT, and mTOR signaling. We also tested the utility of EC359 in treating IBC in vivo using KPL4 xenografts. EC359 (5mg/kg/day) is highly efficacious in reducing IBC xenograft tumor growth in vivo. IHC analyses of tumors confirmed decreased cell proliferation as measured by Ki67 staining. Conclusion: Collectively, these studies demonstrated the therapeutic benefit of using EC359 to target the LIF/LIFR axis and opened the door for the development of new treatment approaches. Citation Format: Bianca Romo, Zenaida Fuentes, Lois Randolph, Bindu Santhamma, Hareesh Nair, Christoforos Thomas, Ratna Vadlamudi, Suryavathi Viswanadhapalli. Significance of LIF/LIFR axis in the progression of inflammatory breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5986.