Vascular endothelial growth factor mediated angiogenic potential of pancreatic ductal carcinomas enhanced by hypoxia: An in vitro and in vivo study

Abstract

Angiogenesis in pancreatic ductal adenocarcinomas depends on the presence of angiogenic factors such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) and is thought to be stimulated by hypoxia. We tested the angiogenic potential of 9 cell lines of pancreatic ductal carcinoma origin by screening mRNA and protein expression of VEGF and bFGF and the release of VEGF into culture medium under normoxic and hypoxic (5% or 0.2% O 2 ) conditions. Angiogenic activity was determined using 2-and 3-D endothelial cell assays. Furthermore, VEGF expression and tumor vascularization were studied in human pancreatic carcinoma tissues from orthotopic xenografts and resection specimens. All cell lines expressed (mRNA, protein) and secreted VEGF, whereas bFGF was only found in 3 cell lines and was secreted into the medium in low concentrations. In addition to the dominant isoforms VEGF 121 ,VEGF 165 and VEGF 189 , 2 isoforms described recently, VEGF 145 and VEGF 183 , were detected. Severe hypoxia (0.2% O 2 ), but not moderate hypoxia (5% O 2 ) raised VEGF mRNA expression and protein secretion in 7/9 and 5/9 cell lines, respectively. Conditioned media from 7/9, 6/9, 8/9 and 7/9 cell lines stimulated endothelial cell proliferation under normoxic (24 and 48 hr) or hypoxic (24 hr, 0.2% and 48 hr 5% O 2 ) conditions, respectively. Conditioned media from 4/9 cell lines also induced capillary-like sprouting under normoxic conditions and from 6/9 under hypoxic (0.2% O 2 ) conditions. In xenografted carcinoma tissues microvessel density was found not to be increased around areas of ischemic necrosis. In resected ductal carcinomas showing tumor necrosis VEGF expression and microvessel density were only increased in 3/12 and 2/13 cases, respectively. In conclusion, in vitro most pancreatic ductal carcinomas show a distinct VEGF related angiogenic potential, as demonstrated by 2-and 3-D endothelial cell proliferation, which may be promoted by severe hypoxia. Surprisingly, perinecrotic tumor areas, which are supposed to be hypoxic, only rarely showed the expected increase in microvessel density and VEGF expression.

VEGF expression by mesenchymal stem cells contributes to angiogenesis in pancreatic carcinoma

“…These consisted of MIA-PaCa-2 pancreatic cancer cells, primary fibroblasts, and HUVECs. Pancreatic cancer cells and fibroblasts are known to overexpress many growth factors (Korc, 2007), including VEGF (Sipos et al, 2002). This, in turn, may lead to the paracrine stimulation of PDGF expression in HUVECs as recently described (Reinmuth et al, 2007).…”

Gastrin Enhances the Angiogenic Potential of Endothelial Cells via Modulation of Heparin-Binding Epidermal-Like Growth Factor

“…This hypothesis could be explained by a number of factors, including degree of CCK-2R expression, vessel composition, differential cellular interactions, and expression of endogenous gastrin peptides. It also suggests that raised serum gastrin levels may increase angiogenic activity close to the tumor sites, possibly aiding in capillary sprouting into areas of hypoxia/necrosis (39)(40)(41)(42).…”

VEGF expression in pancreatic cancer and other malignancies: a review of the literature

“…In vitro, most pancreatic ductal carcinomas show a distinct VEGF related angiogenic potential, as demonstrated by 2-and 3-D endothelial cell proliferation, which may be promoted by severe hypoxia. Surprisingly, perinecrotic tumor areas, which are supposed to be hypoxic, only rarely showed the expected increase in microvessel density and VEGF expression [80]. VEGF-A gene locus analysis across 80 human tumour types reveals VEGF-A gene alterations were predominantly observed in hepatocarcinomas, adenocarcinomas of the pancreas and intestine, large cell carcinoma of the lung and in endometrium serous carcinoma [81].…”