Concomitant over-expression of vascular endothelial growth factor and its receptors in pancreatic cancer

Vascular endothelial growth factor (VEGF) is a potent angiogenic polypeptid e that activates 2 distinct high-affinity tyrosine kinase receptors, flk-I/ KDR and fit-I. In the present study, we characterized the expression of VEG F and its receptors flk-I/KDR and fit-I in the normal human pancreas and in human pancreatic cancer tissues and cell lines. VEGF, flk-I/KDR and fit-I mRNA levels were elevated in cancer tissues compared with normal pancreas. By immuno-histochemistry, VEGF, flk-I/KDR and fit-I immunoreactivity coloca lized in many of the cancer cells within the tumor mass. Three (AsPG-I, Gap an-I and MlAPaCa-2) of 6 pancreatic cancer cell lines expressed flk-I/KDR m RNA and protein, and 4 cell lines (AsPG-I, Gapan-I,T3M4 and PANG-I) express ed fit-I mRNA transcripts. Binding studies with (125)l-labeled VEGF165 indi cated that only Gapan-I cells exhibited high levels of specific binding. Fu rthermore, VEGF enhanced the growth of Gapan-I cells hut was without effect in the other cell lines. VEGF also enhanced mitogen-activated protein kina se (MAPK) phosphorylation and c-fos induction in Gapan-I cells, whereas the MAPK kinase inhibitor PD98059 abolished the growth-stimulatory effect of V EGF. These data indicate that human pancreatic cancers have the capacity to over-express VEGF and its receptors and suggest that in some instances VEG F may directly promote pancreatic cancer growth via the MAPK pathway. (C) 2 000 Wiley-Liss, Inc.