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Published on: July 20, 2019
Effects of interferon alpha on vascular endothelial growth factor gene transcription and tumor angiogenesis
Zofia von Marschall1, Arne Scholz, Thorsten Cramer
1Department of Hepatology, Gastroenterology, Endocrinology and Metabolism, Charité, Campus Virchow-Klinikum, Humboldt-University, Berlin, Germany.
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.
Conclusion:
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.
Insights
Interferon alpha (IFN-alpha) inhibits neuroendocrine tumor growth by reducing blood vessel formation. This occurs through blocking vascular endothelial growth factor (VEGF) gene expression, mediated by Sp1/Sp3 transcription factors.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Research
Background:
- Interferon alpha (IFN-alpha) exhibits antiangiogenic properties, but its mechanism in neuroendocrine (NE) tumors is not fully understood.
- Neuroendocrine tumors are highly vascular and respond to IFN-alpha therapy.
- Investigating IFN-alpha's effect on angiogenesis via vascular endothelial growth factor (VEGF) in NE tumors is crucial.
Purpose of the Study:
- To determine if IFN-alpha's therapeutic effect in NE tumors is due to inhibition of angiogenesis.
- To investigate the role of vascular endothelial growth factor (VEGF) gene expression in this process.
- To elucidate the molecular mechanism by which IFN-alpha affects VEGF transcription.
Main Methods:
- Analysis of VEGF gene and protein expression in NE tumors and cell lines using immunohistochemistry, RT-PCR, and ELISA.
- Utilized VEGF promoter-reporter gene assays and gel shift assays to identify regulatory elements and transcription factors.
- Evaluated IFN-alpha's impact on tumor growth and microvessel density in a xenograft mouse model and analyzed patient liver metastases.
Main Results:
- NE tumors express and secrete VEGF. IFN-alpha treatment reduced VEGF gene transcription via Sp1/Sp3-dependent inhibition of the VEGF promoter.
- In vivo, IFN-alpha inhibited tumor growth by 36% and decreased microvessel density in mice.
- Patients treated with IFN-alpha showed reduced VEGF plasma levels, VEGF mRNA, and microvessel density in liver metastases.
Conclusions:
- IFN-alpha exerts antitumor effects partly through antiangiogenesis.
- This antiangiogenic activity stems from the inhibition of VEGF gene transcription.
- The mechanism involves Sp1 and/or Sp3 transcription factors, highlighting a targeted approach for NE tumor therapy.
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