Vascular endothelial growth factor C promotes human gastric carcinoma lymph node metastasis in mice

Vascular endothelial growth factor (VEGF)-C, one of several members of the VEGF family, is a relatively specific lymphangiogenic growth factor. VEGF receptor (VEGFR)-3 (or Flt4) is a VEGF-C receptor with expression restricted to lymphatic endothelial cells. Since the mechanisms by which carcinoma cells metastasize to lymph nodes remain unclear, we constructed a VEGF-C transfectant (AZ-VEGF-C) from the AZ521 human gastric carcinoma cell line, which ordinarily shows little nodal metastatic potential and little VEGF-C expression. We orthotopically implanted transfected tumor cells into the stomachs of nude mice. The number of mice developing lymph node metastases and the number of lymph node metastases per mouse with nodal metastases were higher than with implants of mock-transfected control cells. Specifically, percentages of mice with lymph node metastases were 95.5% (21/22) for AZ-VEGF-C and 29.4% (5/17) for controls (P<0.01), while mean numbers of involved lymph nodes were 3.76 for AZ-VEGF-C and 1.00 for controls (P<0.01). No difference was found between AZ-VEGF-C and controls regarding cell growth and chemotactic responses in vitro, or in volumes of tumors arising from implanted cells. When we performed immunohistochemical staining for VEGFR-3 in these tumors to investigate lymphangiogenesis by VEGF-C, the number of vessels stained for VEGFR-3 in tumors and surrounding tissues was higher for AZ-VEGF-C than for controls. VEGFR-3-positive vessels occupied 14.9/1000 of microscopically examined areas for AZ-VEGF-C, but only 1.30/1000 for controls (P<0.001). Our results suggest that VEGF-C is a specific lymphangiogenic growth factor with an important role in lymph node metastasis.