The present invention is directed to an isolated polypeptide including: (1) the A subunit of Shiga-like bacterial toxin, wherein said subunit has the nucleic acid sequence of SEQ ID NO:9; and (2) human vascular endothelial growth factor wherein the growth factor has the nucleic acid sequence of SEQ ID NO:10; wherein the isolated polypeptide possesses ribosome inactivating activity. The present invention is also directed to compositions for inhibiting endothelial cell growth in a patient.