EC359 Enhances Trametinib Efficacy in Ras/Raf-Driven Ovarian Cancer by Suppressing LIFR Signaling.

Ovarian cancer (OCa) remains the most lethal gynecologic malignancy in the United States, with low-grade serous and mucinous subtypes frequently driven by KRAS mutations. These mutations activate downstream MAPK and PI3K/AKT signaling pathways, contributing to tumor progression and resistance to therapy. Although the MEK inhibitor trametinib is used to target these pathways, its efficacy is limited in KRAS-mutant OCa due to compensatory activation of the leukemia inhibitory factor (LIF)/LIF receptor (LIFR) axis. In this study, we evaluated the therapeutic potential of combining trametinib with EC359, a selective LIFR inhibitor, in Ras/Raf-driven OCa models. EC359 significantly reduced cell viability, clonogenic survival, and induced cell death via ferroptosis in vitro. Mechanistic studies revealed that EC359 suppressed trametinib-induced activation of LIFR downstream signaling. RNA-seq analysis showed that combination therapy downregulated mitochondrial translation and MYC target genes while upregulating apoptosis-related genes. In vivo, EC359 and trametinib co-treatment significantly reduced tumor growth in xenograft and PDX models without inducing toxicity. Our studies identify LIFR signaling as a critical vulnerability in Ras/Raf-mutant and low grade serous OCa. Further, it provides strong preclinical rationale for EC359 and trametinib combination therapy as a new therapeutic strategy for treating Ras/Raf-driven OCa and low-grade serous OCa.