ABSTRACT
The angiogenic factor vascular endothelial growth factor-D (VEGF-D) isa ligand for VEGF receptor-3 (VEGFR-3/Flt-4) and receptor-2 (VEGFR-2/KDR)and is implicated in the development of lymphatic vessels and promotion of lymphatic metastases. We assessed the expression of VEGF-D and VEGFR-3 in relation to microvessel density (MVD) in colorectal carcinomas (CRC), adenomas, and adjacent normal tissue by immunohistochemistry on consecutive archival sections. VEGF-D was detected in malignant and benign epithelium and in some smooth muscle of the colorectum. High-grade VEGF-D expression was observed frequently (74%) in CRC compared with adenomas (0%) and adjacent normal mucosa (22%). High-grade VEGF-D expression was not correlated with MVD, Dukes' stage (A to C), or tumor differentiation, but was associated with lymphatic involvement and patient survival. By multivariate analysis, VEGF-D expression was found to be an independent prognostic factor for both disease-free and overall survival. VEGFR-3 expression was detected in a subset of vessels, typically thin-walled and devoid of RBCs, in 89% of CRC cases examined. VEGFR-3-positive vessel densities increased progressively from normal mucosa to adenomas and carcinomas and were correlated with MVD, but not with Dukes' stage (A to C), tumor differentiation, or VEGF-D expression. VEGFR-3 expression was spatially associated with macrophage-rich inflammatory infiltrates, which were significantly more frequent among VEGFR-3-positive cases. We conclude that VEGF-D expression, but not that of its receptor VEGFR-3, is an independent prognostic indicator in CRC. VEGF-D expression may be associated with disease outcome through the promotion of lymphatic involvement/metastases.
