Emerging Implications of Phase Separation in Cancer

Phase separation-mediated biomolecular condensates and their relationship to tumor

Phase separation is a cellular phenomenon where macromolecules aggregate or segregate, giving rise to biomolecular condensates resembling "droplets" and forming distinct, membrane-free compartments. This process is pervasive in biological cells, contributing to various essential cellular functions. However, when phase separation goes awry, leading to abnormal molecular aggregation, it can become a driving factor in the development of diseases, including tumor. Recent investigations have unveiled the intricate connection between dysregulated phase separation and tumor pathogenesis, highlighting its potential as a novel therapeutic target. This article provides an overview of recent phase separation research, with a particular emphasis on its role in tumor, its therapeutic implications, and outlines avenues for further exploration in this intriguing field.

[Research Progress in the Role of Liquid-Liquid Phase Separation in Human Cancer]

Liquid-liquid phase separation (LLPS) is a reversible process, during which biological macromolecules, including proteins and nucleic acids, condense into liquid membraneless organelles under the influence of weak multivalent interactions. Currently, fluorescence recovery after photobleaching is the primary method used to detect the phase separation of biological macromolecules. Recent studies have revealed the link between abnormal LLPS and the pathogenesis and development of various human cancers. Through phase separation or abnormal phase separation, tumor-related biological macromolecules, such as mRNA, long noncoding RNAs (lncRNAs), and tumor-related proteins, can affect transcriptional translation and DNA damage repair, regulate the autophagy and ferroptosis functions of cells, and thus regulate the development of various tumors. In this review, we summarized the latest research findings on the mechanism of LLPS in the pathogenesis and progression of tumors and elaborated on the promotion or inhibition of autophagy, tumor immunity, DNA damage repair, and cell ferroptosis after abnormal phase separation of biomolecules, including mRNA, lncRNA, and proteins, which subsequently affects the pathogenesis and progression of tumors. According to published findings, many biological macromolecules can regulate transcriptional translation, expression, post-transcriptional modification, cell signal transduction, and other biological processes through phase separation. Therefore, further expansion of the research field of phase separation and in-depth investigation of its molecular mechanisms and regulatory processes hold extensive research potential.

Targeting Biomolecular Condensation and Protein Aggregation against Cancer

Biomolecular condensates, membrane-less entities arising from liquid-liquid phase separation, hold dichotomous roles in health and disease. Alongside their physiological functions, these condensates can transition to a solid phase, producing amyloid-like structures implicated in degenerative diseases and cancer. This review thoroughly examines the dual nature of biomolecular condensates, spotlighting their role in cancer, particularly concerning the p53 tumor suppressor. Given that over half of the malignant tumors possess mutations in the TP53 gene, this topic carries profound implications for future cancer treatment strategies. Notably, p53 not only misfolds but also forms biomolecular condensates and aggregates analogous to other protein-based amyloids, thus significantly influencing cancer progression through loss-of-function, negative dominance, and gain-of-function pathways. The exact molecular mechanisms underpinning the gain-of-function in mutant p53 remain elusive. However, cofactors like nucleic acids and glycosaminoglycans are known to be critical players in this intersection between diseases. Importantly, we reveal that molecules capable of inhibiting mutant p53 aggregation can curtail tumor proliferation and migration. Hence, targeting phase transitions to solid-like amorphous and amyloid-like states of mutant p53 offers a promising direction for innovative cancer diagnostics and therapeutics.

Biomolecule-Based Coacervates with Modulated Physiological Functions

Liquid-liquid phase separation (LLPS) exists widely in living systems, and understanding the working mechanisms of the formed condensed droplets is of great significance for the prevention and treatment of diseases as well as for the development of biomimetic materials. Herein, in this Perspective we try to focus on the in vitro reconstructions of biomolecule-based coacervates and outline the associations between the functional components and droplets as well as the physiological and pathological functions associated with coacervates. Coacervates are formed by functional components through weak, multivalent interactions. The interaction strengths that determine coacervate properties such as electability and phase state, which in turn influence the functional components to limit their fluidity, stability, or diffusion coefficients, are specially discussed. At the end of this Perspective, the current challenges are summarized; progress will require our great efforts to reveal the mechanisms of action at the molecular level and then develop biomolecule-based coacervate models with complexity, integration of methods, and intellectualization.

Liquid-liquid phase separation throws novel insights into treatment strategies for skin cutaneous melanoma

BACKGROUND

In recent years, there has been growing evidence indicating a relationship between liquid-liquid phase separation (LLPS) and cancer development. However, to date, the clinical significance of LLPS in skin cutaneous melanoma (SKCM, hereafter referred to as melanoma) remains to be elucidated. In the current study, the impact of LLPS-related genes on melanoma prognosis has been explored.

METHODS

LLPS-related genes were retrieved from the DrLLPS database. The prognostic feature for LLPS in melanoma was developed in The Cancer Genome Atlas (TCGA) dataset and verified in the GSE65904 cohort. Based on risk scores, melanoma patients were categorized into high- and low-risk groups. Thereafter, the differences in clinicopathological correlation, functional enrichment, immune landscape, tumor mutational burden, and impact of immunotherapy between the two groups were investigated. Finally, the role of key gene TROAP in melanoma was validated by in vitro and in vivo experiments.

RESULTS

The LLPS-related gene signature was developed based on MLKL, PARVA, PKP1, PSME1, RNF114, and TROAP. The risk score was a crucial independent prognostic factor for melanoma and patients with high-risk scores were related to a worse prognosis. Approximately, all immune-relevant characteristics, such as immune cell infiltration and immune scores, were extremely evident in patients with low-risk scores. The findings from the in vitro and in vivo experiments indicated that the viability, proliferation, and invasion ability of melanoma cells were drastically decreased after the knockdown of TROAP.

CONCLUSION

Our gene signature can independently predict the survival of melanoma patients. It provides a basis for the exploration of the relationship between LLPS and melanoma and can offer a fresh perspective on the clinical diagnosis and treatment of the disease.

Phase separation in cancer at a glance

Eukaryotic cells are segmented into multiple compartments or organelles within the cell that regulate distinct chemical and biological processes. Membrane-less organelles are membrane-less microscopic cellular compartments that contain protein and RNA molecules that perform a wide range of functions. Liquid-liquid phase separation (LLPS) can reveal how membrane-less organelles develop via dynamic biomolecule assembly. LLPS either segregates undesirable molecules from cells or aggregates desired ones in cells. Aberrant LLPS results in the production of abnormal biomolecular condensates (BMCs), which can cause cancer. Here, we explore the intricate mechanisms behind the formation of BMCs and its biophysical properties. Additionally, we discuss recent discoveries related to biological LLPS in tumorigenesis, including aberrant signaling and transduction, stress granule formation, evading growth arrest, and genomic instability. We also discuss the therapeutic implications of LLPS in cancer. Understanding the concept and mechanism of LLPS and its role in tumorigenesis is crucial for antitumor therapeutic strategies.