Phase separation and the tumor microenvironment.

Liquid-Liquid Phase Separation (LLPS) is a physicochemical process which involves biomolecules spontaneously assembling into membrane-less biomolecular condensates through multivalent weak interactions. It emerges as a key factor regulating cellular homeostasis, and is widely involved in the spatiotemporal regulation of core cellular activities including gene expression and signal transduction. Notably, the dynamic process of LLPS is highly sensitive to extracellular microenvironmental cues, especially in the context of cancer. The Tumor Microenvironment (TME) is a dynamically heterogeneous environment characterized by metabolic dysregulation such as lactate accumulation and acidosis, hypoxia, nutrient deprivation, cytokine imbalance, and abnormal physicochemical signals. Accumulating evidence indicates that this specialized microenvironment exerts a profound regulatory effect on LLPS dynamics. This review systematically analyzes the bidirectional interaction between LLPS and TME, as well as the emerging opportunities to understand and influence tumor progression and emergence of therapeutic resistance by focusing on TME-LLPS crosstalk. We also highlight core challenges in this field, including the heterogeneity of LLPS and the associated dynamic processes, and the lack of tools for accurately monitoring condensate behavior in vivo. These opportunities and challenges motivate future research directions, focusing on the development of high-resolution LLPS imaging technologies, single-cell LLPS omics technologies, and therapeutic approaches targeting vulnerable sites of TME-LLPS such as YAP-TEAD condensate disruptors and pH-responsive modulators. Deciphering the LLPS-TME regulatory network is expected to provide support for redefining tumor heterogeneity and promoting the development of precision oncology.