Vascular endothelial growth factor and lymph node metastasis in primary lung cancer

The relationship between vascular endothelial growth factor (VEGF) and lymph node metastasis was studied in 90 cases of primary lung cancer without distant metastasis. As a result of quantitative reverse transcription polymerase chain reaction (RT-PCR) analysis, the VEGF121 mRNA expression levels in lung cancer tissues with nodal metastasis (n = 35) were higher than in those without nodal metastasis (n = 55). However, no significant difference could be found in VEGF121 mRNA expression levels as stratified by tumour size (T1N0M0 vs T2N0M0). Simultaneously, ten lymph nodes (four node positive and six node negative) together with the corresponding primary lung tumours and adjacent normal lung tissue, were studied for VEGF expression. The VEGF mRNA expression in metastatic lymph nodes was intense in three out of the four cases examined. Further, while VEGF expression levels in metastatic lymph nodes were conspicuously higher than those for the primary site, all its expression levels in non-metastatic nodes were inferior to those of the primary tumours. Except for macrophages, the VEGF antigen was identified mainly in the cytoplasm of metastatic cancer cells and the endothelial cells of blood or lymphatic vessels in lymph nodes. Although the detailed mechanisms and the significance of strong VEGF expressions in metastatic lymph nodes are still unknown, these data are consistent with a model whereby VEGF increases the opportunity for nodal metastasis through neoblood and lymphatic vessels.