Related Experiment Videos
Nitric oxide synthase II gene disruption: implications for tumor growth and vascular endothelial growth factor
T E Konopka1, J E Barker, T L Bamford
1Department of Pharmacology, University of Melbourne, Victoria, Australia.
Abstract:
The expression of a primary initiator of tumor angiogenic responses, vascular endothelial growth factor (VEGF), may be induced by nitric oxide (NO) in carcinoma cells. However, the net impact of NO on carcinogenesis remains unclear, because manipulation of NO levels has been shown to either stimulate or inhibit tumor growth. We have investigated the relationship between inducible NO synthase (NOS II), VEGF expression, and growth of B16-F1 melanoma over 14 days in wild-type (NOS II+/+) mice and in those in which the gene for NOS II has been deleted (NOS II-/-). B16-F1 tumor growth was measured as wet weight of the excised tissue. Tumor NOS II and VEGF localization were evaluated by immunohistochemistry, and VEGF mRNA levels were measured by Northern blot analysis. In NOS II+/+ mice inoculated with B16-F1 melanoma cells, macroscopic tumors were always observed at 14 days; however, 22% of NOS II-/- mice had no detectable tumor mass. Immunoreactive NOS II was detected in tumor cells of tumors grown in NOS II+/+ but not in NOS II-/- mice. Although immunoreactive VEGF was detected in the granules of tumor-associated mast cells from both NOS II+/+ and NOS II-/- mice, VEGF mRNA expression in tumors from NOS II-/- was half that in NOS II+/+ mice. Neither NOS II inhibition, exogenous NO, nor peroxynitrite influenced DNA synthesis in culture B16-F1 melanoma cells. The NO donor did not alter either VEGF mRNA levels or degranulation in cultures of the mast cell line RBL-2H3, but peroxynitrite increased both VEGF mRNA expression and degranulation. We conclude that host expression of NOS II contributes to induction of NOS II in the tumor and to melanoma growth in vivo, possibly by regulating the amount and availability of VEGF.
Insights
Host expression of inducible nitric oxide synthase (NOS II) promotes melanoma growth by increasing vascular endothelial growth factor (VEGF) expression. Deleting the NOS II gene significantly reduced tumor development in mice, highlighting NOS II
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Nitric oxide (NO) plays a complex role in cancer, potentially influencing tumor angiogenesis and growth.
- Vascular Endothelial Growth Factor (VEGF) is a key initiator of tumor angiogenesis.
- The precise relationship between inducible NO synthase (NOS II), VEGF, and melanoma development requires further elucidation.
Purpose of the Study:
- To investigate the role of inducible NO synthase (NOS II) in the growth of B16-F1 melanoma.
- To determine the impact of NOS II on vascular endothelial growth factor (VEGF) expression in melanoma.
- To elucidate the mechanisms by which NO influences tumor development in vivo.
Main Methods:
- Comparison of B16-F1 melanoma growth in wild-type (NOS II+/+) and NOS II-deficient (NOS II-/-) mice over 14 days.
- Immunohistochemical analysis of tumor NOS II and VEGF localization.
- Quantification of VEGF mRNA levels using Northern blot analysis.
- In vitro studies using B16-F1 melanoma cells and RBL-2H3 mast cells to assess the effects of NO modulation.
Main Results:
- Tumor growth was significantly inhibited in NOS II-/- mice, with 22% showing no detectable tumor mass.
- Immunoreactive NOS II was present in tumors from NOS II+/+ mice but absent in NOS II-/- mice.
- VEGF mRNA levels were reduced by half in tumors from NOS II-/- mice compared to NOS II+/+ mice.
- Peroxynitrite, but not NO donors, increased VEGF mRNA expression and degranulation in mast cells.
Conclusions:
- Host NOS II expression contributes to tumor NOS II induction and melanoma growth in vivo.
- NOS II appears to regulate melanoma growth, potentially by modulating VEGF availability.
- These findings suggest that targeting NOS II could be a therapeutic strategy for melanoma.