Primary Tumor Induces Sentinel Lymph Node Lymphangiogenesis in Oral Squamous Cell Carcinoma

The main factor that affects the prognosis of patients with oral squamous cell carcinoma (OSCC) is regional lymph node metastases, which usually spreads first to the sentinel lymph nodes (SLNs). Recent studies have demonstrated that tumor cells in several malignancies can induce lymphangiogenesis in SLNs before metastasizing. To elucidate the mechanisms of tumor dissemination of OSCC, we investigated whether primary tumors induce lymphangiogenesis within SLNs in patients with OSCC. The mRNA expression of lymphatic-specific markers, including VEGFR-3, Prox-1, and LYVE-1 in 23 metastasis-negative SLNs obtained from 10 patients with OSCC, was investigated using a quantitative real-time RT-PCR assay, and compared with control lymph nodes from patients with non-cancerous diseases. In addition, VEGF-C and VEGF-D expressions of the primary tumor were examined by immunohistochemistry. In SLNs, there were highly significant correlations between the three lymphatic markers examined. Interestingly, the level of LYVE-1 expression in SLNs, despite the absence of metastasis, was significantly higher than in control lymph nodes. Moreover, SLNs from patients with VEGF-C-positive tumor showed a significantly higher expression of VEGFR-3 than those from patients with VEGF-C-negative tumor. Our findings suggest that in OSCC, the primary tumor actively induces lymphangiogenesis in SLNs prior to the onset of metastases, and where tumor-derived VEGF-C plays an important role.