Induction of lymphangiogenesis through vascular endothelial growth factor-C/vascular endothelial growth factor receptor 3 axis and its correlation with lymph node metastasis in nasopharyngeal carcinoma

The contribution of the lymphatic system to tumor metastasis is being increasingly appreciated through studies of human cancers. As the biological behavior of nasopharyngeal carcinoma (NPC) depends on its nodal status, patients with advanced nodal status show a higher tendency toward a poor outcome. Here, we examined the role of lymphangiogenesis on lymphatic spread of NPC. We also evaluated the involvement of vascular endothelial growth factor (VEGF)-C/VEGF receptor 3 (VEGFR3) signaling pathway on lymphangiogenesis in NPC. Furthermore, we tested whether Epstein–Barr virus (EBV)-latent membrane protein (LMP) 1 induces VEGF-C. Forty-one patients with NPC were evaluated for expressions of VEGF-C and its receptor, VEGFR3, and LMP1 proteins and lymphatic vessel counts (LVC) highlighted by anti-podoplanin employing immunohistochemistry. The VEGF-C induction by LMP1 was then tested with Western blotting and enzyme-linked immunosorbent assay in vitro. The LVC and VEGF-C expression were significantly higher in cases with advanced regional lymph node metastasis (N2,3) than those with no or limited lymph node involvement (N0,1) (p = 0.0380 and p = 0.0109, respectively). In VEGF-C/VEGFR3-positive cases, the LVC were significantly increased compared with VEGF-C/VEGFR3-negative cases (p = 0.0007). However, LMP1 expression did not show significant associations with LVC and VEGF-C-expression scores (p = 0.1210 and p = 0.1324, respectively). Induction of VEGF-C protein by LMP1 was not detected in vitro. These results suggest the involvement of the VEGF-C/VEGFR3 axis in the induction of lymphangiogenesis which results in lymphatic spread of NPC. However, EBV-LMP1 was not associated with the mechanism.