Impact of oncogenes in tumor angiogenesis: mutant K-ras up-regulation of vascular endothelial growth factor/vascular permeability factor is necessary, but not sufficient for tumorigenicity of human colorectal carcinoma cells. - Okada,F.; Rak,J.W.; St,C.roix B. (Proc Natl Acad Sci U S A, 1998)