In mice expressing a mutant Vegfr2 allele (Vegfr2Y1173F/+) reducing the level of endothelial PLCγ activation by half, the growth rate of melanoma and fibrosarcoma were unaffected, while vascular leakage was markedly reduced, accompanied by better efficiency of low-dose chemotherapy in restricting tumor growth. This evidence concerns the gene KDR and fibrosarcoma.