Effects of interferon alpha on vascular endothelial growth factor gene transcription and tumor angiogenesis.
BACKGROUND
Interferon alpha (IFN-alpha) has antiangiogenic activity, although the underlying mechanism of action is unclear. Because human neuroendocrine (NE) tumors are highly vascularized and sensitive to IFN-alpha, we investigated whether the therapeutic effects of IFN-alpha result from an inhibition of angiogenesis mediated by a decrease in vascular endothelial growth factor (VEGF) gene expression.


METHODS
VEGF gene and protein expression was analyzed in NE tumors by immunohistochemistry and in NE tumor cell lines by quantitative competitive reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). VEGF promoter-reporter gene constructs containing various deletions or mutations and gel shift assays were used to identify minimal promoter requirements and potential transcription factors. A xenograft nude mouse model (five mice per group) was used to determine the effect of IFN-alpha on tumor growth (NE Bon cells and pancreatic Capan-1 cells) and microvessel density. Liver metastases from eight patients with NE tumors were analyzed for microvessel density, VEGF mRNA content, and VEGF plasma levels before and after initiation of IFN-alpha therapy.


RESULTS
NE tumors and cell lines expressed VEGF mRNA and secreted VEGF protein. In vitro, IFN-alpha decreased transcription of VEGF gene expression through an Sp1- and/or Sp3-dependent inhibition of VEGF promoter activity. Compared with vehicle treatment in mice, IFN-alpha inhibited tumor growth by 36% and reduced microvessel density from 56 (95% confidence interval [CI] = 49 to 69) to 37 per x400 Field (95% CI = 32 to 41, P =.015). Patients with NE tumors had lower VEGF plasma levels and reduced VEGF mRNA levels and microvessel density in liver metastasis biopsy material after IFN-alpha treatment.


CONCLUSIONS
IFN-alpha confers its antitumor activity, at least in part, by its antiangiogenic activity, which results from Sp1- and/or Sp3-mediated inhibition of VEGF gene transcription.
von Marschall
Zofia
Z
Department of Hepatology, Gastroenterology, Endocrinology and Metabolism, Charité, Campus Virchow-Klinikum, Humboldt-University, Berlin, Germany.
Scholz
Arne
A
Cramer
Thorsten
T
Schäfer
Georgia
G
Schirner
Michael
M
Oberg
Kjell
K
Wiedenmann
Bertram
B
Höcker
Michael
M
Rosewicz
Stefan
S
D020533:Angiogenesis Inhibitors / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D024202:Electrophoretic Mobility Shift Assay; D016228:Endothelial Growth Factors / Q000235:genetics / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D017930:Genes, Reporter / Q000187:drug effects; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D016898:Interferon-alpha / Q000494:pharmacology*; D008156:Luciferases / Q000378:metabolism; D008222:Lymphokines / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D009389:Neovascularization, Pathologic / Q000188:drug therapy* / Q000378:metabolism; D018358:Neuroendocrine Tumors / Q000098:blood supply / Q000188:drug therapy* / Q000378:metabolism*; D011257:Pregnancy Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D040262:Receptors, Vascular Endothelial Growth Factor / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects*; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D020533:Angiogenesis Inhibitors; D000970:Antineoplastic Agents; D016228:Endothelial Growth Factors; D036341:Intercellular Signaling Peptides and Proteins; D016898:Interferon-alpha; D008222:Lymphokines; D011257:Pregnancy Proteins; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D008156:Luciferases; D040262:Receptors, Vascular Endothelial Growth Factor