Heparin and heparan sulfate are structurally similar glycosaminoglycans that are physiologically relevant and have been used as pharmacological targets, especially in regards to cancer. Heparin interacts with the protein antithrombin III (ATIII) and causes a conformation change that increases its ability to inhibit coagulation factors. Consequently, heparin is used as an anticoagulant. Heparan sulfate is involved in many processes. It is notably involved in cell-to-cell extracellular membrane organization - the process in which cells adhere together - and cell proliferation via growth factor signaling. These roles make it and its related enzymes key targets for drugs meant to prevent cancer metastasis.