This document discusses using a protein from malaria (VAR2CSA) to target cancer cells. VAR2CSA normally binds to a type of sugar (chondroitin sulfate A) that is found in the placenta during pregnancy and protects malaria-infected red blood cells. This same type of sugar is also frequently expressed in certain cancers. The document shows that VAR2CSA can bind to cancer cells, be internalized, and deliver cytotoxic compounds specifically to tumors both in vitro and in vivo. A recombinant VAR2CSA-diphtheria toxin fusion protein was able to significantly inhibit tumor growth in mice with no apparent toxicity. This suggests VAR2CSA may be useful as a targeting system for cancer treatment