Abstract
The growth of solid tumors in vivo beyond 1–2 mm in diameter requires induction and maintenance of an angiogenic response. This can occur through the release of various angiogenic growth factors from tumor cells. One such factor is vascular endothelial growth factor/vascular permeability factor (VEGF/VPF), a secreted and specific mitogen for vascular endothelial cells. We show that one of the most commonly encountered genetic changes detected in human cancer, i.e., expression of mutant ras oncogenes, is associated with marked up-regulation of VEGF/VPF in transformed epithelial cells. Thus, elevation of the levels of both VEGF/VPF mRNA and secreted functional protein were detected in human and rodent tumor cell lines expressing mutant K-ras or H-ras oncogenes, respectively. Genetic disruption of the mutant K-ras allele in human colon carcinoma cells was associated with a reduction in VEGF/VPF activity. Furthermore, pharmacological disruption of mutant RAS protein function in H-ras transformed rat intestinal epithelial cells by treatment with L-739,749 (a protein farnesyltransferase inhibitor) caused a significant suppression of VEGF/VPF. The results suggest that dominantly acting ras oncogenes may contribute to the growth of solid tumors in vivo not only by a direct effect on tumor cell proliferation but also indirectly, i.e., by facilitating tumor angiogenesis. Hence, pharmacologically targeting mutant ras oncogenes could conceivably suppress solid tumor growth in vivo, in part, by inhibiting tumor-induced angiogenesis.
Footnotes
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↵1 This work was supported by grants from the Medical Research Council of Canada and the National Institutes of Health, USA (CA-41233) to RSK. RSK is a Terry Fox Scientist of the National Cancer Institute of Canada, supported by funds from the annual Terry Fox Run.
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↵2 To whom requests for reprints should be addressed, at Sunnybrook Health Science Centre, Reichmann Research Building, S-218, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5 Canada.
- Received September 7, 1995.
- Accepted September 14, 1995.
- ©1995 American Association for Cancer Research.