Hypoxia-inducible factor 1 regulates vascular endothelial growth factor expression in human pancreatic cancer.
BACKGROUND
The microenvironment of low oxygen that is present in human pancreatic cancer in vivo may actively influence tumor growth as well as neovascularization.


OBJECTIVE
To determine whether hypoxia-inducible factor 1 (HIF-1) is specifically activated by hypoxia in vitro in pancreatic cancer cells and correlated these findings with tumor specimens.


METHODS
Hypoxic regulation of vascular endothelial growth factor (VEGF) was studied by northern blot analysis and enzyme-linked immunosorbent assay. Electrophoretic mobility shift assays and western blot analysis were used to demonstrate hypoxic activation of HIF-1. The relationship between HIF-1 and VEGF in human pancreatic cancer specimens was studied by immunohistochemical analysis, northern blot analysis, and in situ hybridization.


RESULTS
Studies in vivo of human pancreatic cancer tissue showed co-localization of VEGF mRNA, which is produced in ductal cancer cells, and HIF-1alpha protein, which was detectable in cell nuclei of the same cells. HIF-1alpha mRNA expression was dramatically upregulated (approximately 13-fold) in these specimens as well. In vitro, all pancreatic cancer cell lines increased VEGF production when exposed to low oxygen levels, by highly specific activation of HIF-1 DNA binding activity to the VEGF promoter. Cancer cell lines with high constitutive levels of HIF-1alpha protein were found to produce higher basal levels of VEGF.


CONCLUSIONS
We conclude that HIF-1 is the regulatory link between tumor hypoxia and VEGF production in pancreatic cancer, thus establishing a biochemical pathway between tumor hypoxia and neoangiogenesis in this highly aggressive neoplasm.
Büchler
Peter
P
Department of Surgery, UCLA School of Medicine, Los Angeles, California 90095-6904, USA.
Reber
Howard A
HA
Büchler
Manuela
M
Shrinkante
Shailesh
S
Büchler
Markus W
MW
Friess
Helmut
H
Semenza
Gregg L
GL
Hines
Oscar J
OJ
D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism; D015687:Cell Hypoxia; D002467:Cell Nucleus / Q000235:genetics; D004268:DNA-Binding Proteins / Q000502:physiology*; D016228:Endothelial Growth Factors / Q000096:biosynthesis / Q000235:genetics*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000235:genetics*; D008222:Lymphokines / Q000096:biosynthesis / Q000235:genetics*; D009687:Nuclear Proteins / Q000502:physiology*; D010190:Pancreatic Neoplasms / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D004268:DNA-Binding Proteins; D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; C497442:HIF1A protein, human; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D019833:Genistein