KDR and neoplasm: The final antitumor effects may be classified as follows: direct cytotoxic effects on tumor cells by induction of cell death, anti-angiogenic effects leading to growth delay and/or tumor regression by cytostatic inhibition of new blood-vessel formation, vascular disruption by inhibition of existing VEGF/VEGFR-dependent tumor blood vessels leading to central tumor cell necrosis, and cavitation that may or may not be associated with tumor regression.