The Macrophage-Associated LncRNA MALR Facilitates ILF3 Liquid–Liquid Phase Separation to Promote HIF1α Signaling in Esophageal Cancer

Abstract Tumor-associated macrophages (TAM) are among the most abundant immune cells in the tumor microenvironment and are important mediators of tumor development and progression. Here, we identified a macrophage-associated long noncoding RNA (lncRNA), MALR, that facilitates progression of esophageal squamous cell carcinoma (ESCC). TAM-mediated secretion of TNFα drove MALR upregulation in ESCC cells. MALR promoted aerobic glycolytic activity and facilitated angiogenesis by activating the HIF1α signaling pathway. Mechanistically, MALR bound the dsRBD1 domain of interleukin enhancer-binding factor 3 (ILF3), promoting ILF3 protein stability and ILF3-mediated liquid–liquid phase separation (LLPS), thereby enhancing HIF1α mRNA stability by preventing PARN-mediated degradation. Loss of MALR suppressed cell line–based and patient-derived xenograft tumor growth. Clinically, high expression of MALR positively correlated with HIF1α target gene expression and indicated poor prognoses for patients with esophageal cancer. Overall, this study uncovers the physiologic roles of MALR/ILF3-mediated LLPS in tumor microenvironment remodeling, highlighting the MALR–ILF3–HIF1α axis as a potential target for cancer therapy. Significance: Secretion of TNFα by tumor-associated macrophages stimulates cancer cells to upregulate lncRNA MALR, which induces ILF3 liquid–liquid phase separation and activation of HIF1α signaling to promote cancer progression.