De novo expression of vascular endothelial growth factor in human pancreatic cancer: Evidence for an autocrine mitogenic loop

Background & Aims: The role of vascular endothelial growth factor (VEGF) an d its receptors in tumor angiogenesis has been well established, We analyze d the expression pattern and biologic significance of VEGF and its receptor s in human pancreatic cancer. Methods: VEGF, KDR/flk-1, and fit-1 expressio n were examined by immunohistochemistry, in situ hybridization, reverse-tra nscription polymerase chain reaction, enzyme-linked immunosorbent assay, an d receptor phosphorylation. VEGF-stimulated mitogenesis was investigated by mitogen-activated protein kinase (MAPK) phosphorylation, transactivation o f a c-fos promoter reporter construct, DNA synthesis assays, and stable tra nsfection of a dominant-negative flk-1 complementary DNA (cDNA) construct. Results: Compared with normal pancreas and chronic pancreatitis, VEGF and i ts receptors were overexpressed in pancreatic cancer. KDR and flt-1 were de tected not only in endothelial cells but also in tumor cells, VEGF expressi on was observed in all human pancreatic tumor cell lines examined, and the KDR/flk-1 and flt-1 receptor was detected in 2 cell lines. VEGF treatment r esults in phosphorylation of MAPKs, transactivation of a c-fos promoter con struct, and growth stimulation in KDR/flk-1-expressing cell lines, which co uld be blocked by VEGF antagonists. Furthermore, stable transfection of a d ominant-negative flk-1 cDNA significantly inhibited tumor cell growth. Conc lusions: These results not only support the important role of the VEGF/VEGF receptor system in pancreatic tumor biology but also suggest the existence of an autocrine/paracrine mitogenic loop for pancreatic cancer cells.