Multidimensional insights into exosomes in hepatocellular carcinoma: from genesis to clinical application

Abstract

Hepatocellular carcinoma (HCC) is a highly aggressive malignancy, whose progression is intimately linked to the complex dynamics of the tumor microenvironment (TME). Exosomes, once considered mere cellular waste, have emerged as pivotal mediators of intercellular communication within the TME, actively participating in the multistep development of HCC. These nanoscale vesicles play crucial roles in the initiation of precancerous lesions and, by transporting drug resistance-related molecules such as proteins and non-coding RNAs, facilitate the acquisition of resistance to chemotherapy and targeted therapies by tumor cells. Moreover, exosomes contribute to the establishment of pre-metastatic niches by remodeling distant organ microenvironments-inducing hypoxia, metabolic reprogramming, and angiogenesis-which collectively create favorable conditions for tumor cell colonization. They also modulate immune responses by inducing T-cell exhaustion, promoting macrophage polarization, and disrupting normal stromal cell functions, thereby constructing an immunosuppressive microenvironment that enables tumor immune evasion. Given their inherent biocompatibility and targeting capabilities, engineered exosomes have shown promise in cancer therapy, serving as carriers for therapeutic molecules and enabling precise drug delivery through surface modifications. Despite significant advancements, challenges remain in elucidating the in vivo regulatory mechanisms of exosomes, standardizing their isolation and purification processes, and evaluating their clinical efficacy. This review examines the multifaceted roles of exosomes in HCC, aiming to bridge mechanistic insights with precision diagnostics and pave new avenues for liver cancer treatment.

Keywords: drug tolerance; exosomes; hepatocellular carcinoma (HCC); metastasis; targeted therapy; tumor microenvironment (TME).

Figure 1

Mechanisms of exosome-mediated multi-drug resistance formation. This figure illustrates the exosome-mediated tumor drug resistance process between donor and recipient cells, which includes three parts:(A) Accelerated drug inactivation:Donor cells with drug metabolizing enzymes release exosomes carrying these enzyme-related substances. These exosomes act on recipient cells to accelerate drug inactivation, conferring drug resistance. (B) Regulation of P-glycoprotein expression and drug efflux pump transfer:Donor cell-derived exosomes carry cargoes that regulate P-gp expression and transfer drug efflux pumps to recipient cells. Recipient cells then expel chemotherapeutic drugs, creating drug resistance. (C) Promotion of tumor progression:Donor cell-derived exosomes carry non-coding RNA and other substances. These exosomes promote cell proliferation, inhibit ferroptosis, induce angiogenesis, and enhance cellular tolerance to drug sensitization in recipient cells, thereby enhancing tumor resistance to chemotherapeutic drugs.

Figure 2

Exosomes promote pre-metastatic miche formation. This figure illustrates how exosomes facilitate the formation of the pre-metastatic niche(PMN) by remodeling the microenvironment of distant organs to create permissive conditions for tumor cell colonization and proliferation. 1) Hypoxic microenvironment modulation:Hypoxia in HCC induces exosome secretion carrying miR-1290, promoting M2 macrophage polarization, upregulating PD-L1, inducing CD8⁺ T cell apoptosis, and driving EMT, enhancing HCC cell migration and invasion. 2) Metabolic reprogramming:Cancer cells can limit glucose uptake by non-tumor cells in the pre-metastatic niche through secreting miR-122-rich vesicles. They can also use this mechanism to inhibit pyruvate kinase (PKM) in pancreatic islet β-cells, reduce insulin secretion, and disrupt glucose homeostasis, which in turn promotes tumor growth.HCC-derived palmitic acid-rich exosomes stimulate hepatic macrophages to secrete TNF, creating a pro-inflammatory milieu that suppresses fatty acid metabolism and oxidative phosphorylation in recipient cells, fostering steatosis and pre-metastatic niche formation. 3) Angiogenesis promotion:Exosomes carrying the protein GP73, as well as miR-3174, RNA LINC00161, and circRNA-100,338, drive neovascularization in distant organs, providing essential nutrient and oxygen supply routes for the survival and proliferation of metastatic tumor cells.

Figure 3

Exosome promotes tumor immunosuppressive microenvironment. This figure demonstrates the exosome-mediated interactions between different cells in the tumor microenvironment and the related immunomodulatory processes. 1) Tumor-associated macrophages (TAMs) exist in both M1 and M2 phenotypes.M1 to M2 conversion.M1 TAMs can be converted to M2 TAMs through exosome-carried circTMEM181 and miR-1290. Then, M2 TAMs secrete cytokines such as G-CSF, GM-CSF, VEGF, MCP-1, IL-4, etc. 2) Natural killer (NK) cells release circUHRH1, miR-552-5p through exosomes that act on other cells and affect the tumor microenvironment.NK cells also release granzyme and interferon-γ. 3) N1 cells can be transformed into N2 cells by exosome-borne circPACRGL. 4) MSCs receive exosomes from other cells, such as exosomes carrying miR-122, miR-15a, which can induce tumor death. 5) Exosomes from endothelial progenitor cells exert their effects by inhibiting THBS1 via miR-210, and miR-210, which is highly expressed in HCC cell-derived exosomes, targets SMAD4 and STAT6 in endothelial cells to promote angiogenesis. In addition, tumor-derived exosomes activate platelets to promote coagulation and metastasis, while platelet exosomes can enhance VEGF mRNA expression in cancer cells and their adhesion to endothelial cells. These findings demonstrate the intricate interactions between endothelial cells and platelets in the tumor microenvironment and their important roles in promoting tumor dissemination and growth. 6) CAFs are key drivers of tumor progression. They exert their effects through exosomes: for instance, miR-92a-3p in CAF-derived exosomes can target AXIN1 to activate the β-catenin/CD44 signaling pathway in HCC, and in colorectal cancer, it can activate the Wnt/β-catenin pathway while inhibiting mitochondrial apoptosis by suppressing FBXW7 and MOAP1, thereby enhancing epithelial-mesenchymal transition (EMT) and stemness. Additionally, circHIF1A in exosomes derived from hypoxia-induced CAFs can upregulate PD-L1 in a HuR-dependent manner, promoting immune escape and the development of HCC.CAFs receive exosome-carried miRNA-21, circ-ZEB1, circ-AFAP1.CAFs secrete VEGF, MMP2, MMP9, FGF, and TGF-β, which affect th TME.7)Tumor cells associated with T cells.Tumor cells interact with CD8⁺ T cells through microvesicles.PD-L1 on the surface of tumor cells binds to PD-1 on the surface of CD8⁺ T cells.CD8⁺ T cells receive exosomes carrying miR-25-3p, miR-155-5p, miR-215-5p, miR375. CD4⁺ T cells can be transformed into regulatory T cells.

Figure 4

Engineered exosome drug delivery system construction. This figure shows the preparation of drug-loaded exosomes through seven key steps to boost drug loading efficiency and exosomal stability for effective therapy. 1) Drug co-incubation:Exosomes are co-incubated with therapeutic agents to enable drug adsorption or internalization, facilitating initial drug binding to the exosomal membrane. 2) Ultrasonication:Ultrasonication treats the exosome-drug mixture, enhancing drug penetration into the exosomal membrane and improving loading capacity. 3) Electroporation:Electric fields create transient pores in the membrane, driving drug molecules into the exosomal lumen, especially suitable for hydrophilic drugs. 4) Freeze-thawing cycle:Alternating freezing and thawing increases membrane fluidity and permeability, promoting drug incorporation. 5) Extrusion:Exosomes are forced through narrow channels or membranes, enhancing membrane deformability and encapsulation efficiency via mechanical stress. 6) Transfection:Liposomes or other reagents deliver therapeutic RNA into exosomes, suitable for loading genetic materials. 7) Saponin-mediated loading:Saponin disrupts cell membranes to facilitate drug uptake by exosomes, enhancing internalization for novel nanoscale drug delivery systems.