Exosomal HMGA2 protein from EBV-positive NPC cells destroys vascular endothelial barriers and induces endothelial-to-mesenchymal transition to promote metastasis.

Increased vascular permeability facilitates metastasis. Cancer-secreted exosomes are emerging mediators of cancer-host crosstalk. Epstein-Barr virus (EBV), identified as the first human tumor-associated virus, plays a crucial role in metastatic tumors, especially in nasopharyngeal carcinoma (NPC). To date, whether and how exosomes from EBV-infected NPC cells affect vascular permeability remains unclear. Here, we show that exosomes from EBV-positive NPC cells, but not exosomes from EBV-negative NPC cells, destroy endothelial cell tight junction (TJ) proteins, which are natural barriers against metastasis, and promote endothelial-to-mesenchymal transition (EndMT) in endothelial cells. Proteomic analysis revealed that the level of HMGA2 protein was higher in exosomes derived from EBV-positive NPC cells compared with that in exosomes derived from EBV-negative NPC cells. Depletion of HMGA2 in exosomes derived from EBV-positive NPC cells attenuates endothelial cell dysfunction and tumor cell metastasis. In contrast, exosomes from HMGA2 overexpressing EBV-negative NPC cells promoted these processes. Furthermore, we showed that HMGA2 upregulates the expression of Snail, which contributes to TJ proteins reduction and EndMT in endothelial cells. Moreover, the level of HMGA2 in circulating exosomes is significantly higher in NPC patients with metastasis than in those without metastasis and healthy negative controls, and the level of HMGA2 in tumor cells is associated with TJ and EndMT protein expression in endothelial cells. Collectively, our findings suggest exosomal HMGA2 from EBV-positive NPC cells promotes tumor metastasis by targeting multiple endothelial TJ and promoting EndMT, which highlights secreted HMGA2 as a potential therapeutic target and a predictive marker for NPC metastasis.

Epstein-Barr Virus Induces Lymphangiogenesis and Lympth Node Metastasis via Upregulation of VEGF-C in Nasopharyngeal Carcinoma.

Lymphatic metastasis is a common clinical symptom in nasopharyngeal carcinoma (NPC), the most common Epstein-Barr virus (EBV)-associated head and neck malignancy. However, the effect of EBV on NPC lymph node (LN) metastasis is still unclear. In this study, we demonstrated that EBV infection is strongly associated with advanced clinical N stage and lymphangiogenesis of NPC. We found that NPC cells infected with EBV promote LN metastasis by inducing cancer-associated lymphangiogenesis, whereas these changes were abolished upon clearance of EBV genomes. Mechanistically, EBV-induced VEGF-C contributed to lymphangiogenesis and LN metastasis, and PHLPP1, a target of miR-BART15, partially contributed to AKT/HIF1a hyperactivity and subsequent VEGF-C transcriptional activation. In addition, administration of anti-VEGF-C antibody or HIF1α inhibitors attenuated the lymphangiogenesis and LN metastasis induced by EBV. Finally, we verified the clinical significance of this prometastatic EBV/VEGF-C axis by determining the expression of PHLPP1, AKT, HIF1a, and VEGF-C in NPC specimens with and without EBV. These results uncover a reasonable mechanism for the EBV-modulated LN metastasis microenvironment in NPC, indicating that EBV is a potential therapeutic target for NPC with lymphatic metastasis. IMPLICATIONS: This research demonstrates that EBV induces lymphangiogenesis in NPC by regulating PHLPP1/p-AKT/HIF1a/VEGF-C, providing a new therapeutic target for NPC with lymphatic metastasis.