KDR and neoplasm: The hypothetical anti-angiogenic and anti-tumour effects of low-dose metronomic chemotherapy regimens in mice can be amplified significantly by the concurrent administration of a second drug that is highly specific for activated endothelial cells (e.g., antibodies to vascular endothelial growth factor receptor-2 [VEGFR-2], PEX [C-terminal hemopexin-like domain of matrix metalloproteinase (MMP)-2], anti-VEGF antibodies, and anti-endoglin antibodies).