Nidogen 1-enriched extracellular vesicles drive HCC progression by inducing mregDC differentiation and Treg infiltration.

Aim: Nidogen 1 (NID1) is a secreted pro-tumorigenic protein. While extracellular vesicle (EV)-NID1 is known to accelerate hepatocellular carcinoma (HCC) progression, its role in reshaping the HCC immune microenvironment remains undefined. This study investigated how EV-NID1 modulates dendritic cells (DCs) to establish an immunosuppressive niche that drives liver cancer growth. Methods: The TIMER3.0 database was used to assess the correlations of NID1 with DCs and regulatory T cells (Tregs). A Transwell co-culture system using bone marrow-derived DCs was employed to evaluate the paracrine effects of HCC cells. EVs were isolated by differential ultracentrifugation, and their identity and purity were verified. Orthotopic and subcutaneous HCC mouse models were established to assess immune cell infiltration in vivo. DC adoptive transfer and Treg depletion assays were conducted to elucidate the underlying mechanism. Results: High NID1 expression in HCC was associated with increased infiltration of myeloid DCs and Tregs, and their co-occurrence predicted poor patient survival. In vitro, EV-NID1 induced DC maturation and promoted their polarization toward mature DCs enriched in immunoregulatory molecules (mregDC), accompanied by elevated secretion of C-C chemokine ligand 17 (CCL17). These polarized DCs promoted CD4+ T cell proliferation and FOXP3+ Treg formation. In vivo, NID1-high tumors exhibited accelerated growth and increased infiltration of mregDCs and Tregs in tumors, lymph nodes, and spleens. NID1 knockdown reduced tumor growth, whereas adoptive transfer of EV-NID1-pulsed DCs partially rescued tumor progression. Furthermore, Treg depletion markedly suppressed the growth of NID1-high tumors. Conclusions: This study suggests that NID1-enriched EVs derived from HCC promote tumor progression by inducing a regulatory phenotype in DCs and the expansion of Tregs.