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 r eceptor (VEGFR)-3 (or Flt4) is a VEGF-C receptor with expression restricted to lymphatic endothelial cells. Since the mechanisms by which carcinoma ce lls metastasize to lymph nodes remain unclear, we constructed a VEGF-C tran sfectant (AZ-VEGF-C) from the AZ521 human gastric carcinoma cell line, whic h ordinarily shows little nodal metastatic potential and little VEGF-C expr ession. We orthotopically implanted transfected tumor cells into the stomac hs of nude mice. The number of mice developing lymph node metastases and th e number of lymph node metastases per mouse with nodal metastases were high er than with implants of mock-transfected control cells. Specifically, perc entages 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 lym ph nodes were 3.76 for AZ-VEGF-C and 1.00 for controls (P<0.01). No differe nce was found between AZ-VEGF-C and controls regarding cell growth and chem otactic 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 st ained for VEGFR-3 in tumors and surrounding tissues was higher for AZ-VEGF- C than for controls. VEGFR-3-positive vessels occupied 14.9 parts per thous and of microscopically examined areas for AZ-VEGF-C, but only 1.30 parts pe r thousand for controls (P<0.001). Our results suggest that VEGF-C is a spe cific lymphangiogenic growth factor with an important role in lymph node me tastasis.