Abstract 4966: Targeting LIF/LIFR autocrine loops with EC359 in ovarian cancer: A novel LIFR targeted therapy

Abstract Background: Of all gynecologic cancers, ovarian cancer (OCa) has the highest mortality rates. Nearly 90% of patients who receive standard surgical and cytotoxic treatment experience disease recurrence. Leukemia inhibitory factor (LIF) and its receptor LIFR are implicated in the progression of several cancers. A knowledge gap exists on whether LIF/LIFR plays a role in the evolution of OCa. We recently developed EC359, a first-in-class LIFR inhibitor. Here, we examined whether autocrine loops of LIF/LIFR contribute to OCa progression and tested the utility of EC359 as a potential targeted therapy. Methods: Eighteen different OCa model cells, both established and primary, were used to profile the expression of LIF and LIFR. Cell viability, colony formation, apoptosis, and reporter assays were used to assess EC359 impact on OCa cells. Mechanistic studies were carried out using RNA-seq and RT-qPCR analysis. Using cell-based xenografts, syngeneic xenografts, patient derived organoids (PDO), and patient derived xenograft (PDX) models, the effectiveness of LIFR inhibitor EC359 as a targeted therapy was examined. Results: Kaplan-Meier survival analysis (KMplot) revealed increased expression of LIF and LIFR was linked to poor progression-free survival in OCa patients. The levels of LIF and LIFR were considerably greater in OCa chemotherapy non-responders than responders. We validated the existence of LIF/LIFR autocrine signaling using 18 distinct OCa cells. Treatment with the LIFR inhibitor EC359 dramatically decreased OCa cell viability, cell survival and increased apoptosis, with an IC50 of 5 to 50 nM. The activation of STAT3, mTOR, AKT, and p42/44 MAPKs as well as other downstream LIFR signaling was markedly decreased by EC359 treatment. Treatment with EC359 also decreased the stemness of OCa cells, slowed PDO development, and sensitized chemotherapy-resistant OCa cells to chemotherapy. One of the significant pathways elevated by EC359, according to RNA-seq data, is the regulation of apoptosis. In six different cell-based xenografts and PDX tumors, we demonstrated that the EC359 at 5mg/kg dose significantly reduced the OCa xenograft growth. In comparison to the vehicle control, the tumor volume was significantly reduced by EC359 treatment of murine ID8 xenografts in C57BL6 mice. Our findings indicated that EC359 had both intrinsic and extrinsic effects on tumors. Tumor-associated macrophages (TAMs) with a significant M1 polarity (CD11b+Gr1-CD68high/phosphoSTAT1+/cMAF-) and robust tumor infiltration by (CD45+) leukocytes were enhanced with EC359 therapy of ID8 xenograft tumors. Importantly, normal T, B, and other immune cells in the blood demonstrated that EC359 had no effect on immune cell homeostasis. Conclusions: Together, our findings support the existence of LIF/LIFR autocrine loops, and EC359 is a viable treatment option for OCa. Citation Format: Behnam Ebrahimi, Suryavathi Viswanadhapalli, Uday P. Pratap, Rahul Gopalam, Xue Yang, Bindhu Santhamma, Swapna Konda, Xiaonan Li, Hui Yan, Gangadhara R. Sareddy, Zhenming Xu, Edward R. Kost, Rajeshwar R. Tekmal, Hareesh B. Nair, Ratna K. Vadlamudi. Targeting LIF/LIFR autocrine loops with EC359 in ovarian cancer: A novel LIFR targeted therapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4966.