Small Extracellular Vesicle-Derived Nidogen 1 Promotes HCC Carcinogenesis via Transglutaminase 3-Mediated YAP/TAZ Signalling.

Tumour-derived small extracellular vesicles (sEV) are increasingly recognized as key mediators of cancer progression and metastasis by facilitating intercellular communication. In this study, we identify nidogen 1 (NID1), a basement membrane glycoprotein, as significantly enriched in sEV from metastatic hepatocellular carcinoma (HCC) cells. We demonstrate that the sEV-mediated delivery of NID1 enhances oncogenic behaviours, including proliferation, invasion and metastasis. Knockout mice of NID1 exhibited a marked delay in liver tumour formation induced by N-diethylnitrosamine (DEN) and carbon tetrachloride (CCL4), or hydrodynamic injection delivery of oncogenes, underscoring the role of NID1 in hepatocarcinogenesis. Importantly, we find that a stiffer extracellular matrix, a characteristic of tumour microenvironments, stimulates increased NID1 level in sEV. Using NID1 mutants, we identify the C-terminal domain as critical for its oncogenic functions, including promoting tumour growth and metastasis. Proteomic profiling reveals that transglutaminase 3 (TGM3) interacts with NID1 via its C-terminus. Subsequent analyses indicate that sEV-NID1 elevates TGM3 levels, leading to dysregulation of integrins and activation of the YAP/TAZ signalling pathway, thereby contributing to tumour progression. To explore therapeutic potential, we developed a novel monoclonal anti-NID1 antibody (anti-NID1 mAb) and evaluated its efficacy in multiple HCC mouse models. The antibody markedly suppressed liver tumour growth and metastasis of human and murine HCC cells. The therapeutic effect was further enhanced when combined with sorafenib, a standard treatment for HCC. Our findings delineate a novel sEV-NID1-TGM3 regulatory axis that promotes hepatocarcinogenesis and metastasis and suggest that targeting sEV-delivered NID1 with our homemade monoclonal antibody offers a promising avenue for therapeutic intervention in HCC.