Disclosed herein are compositions comprising a polypeptide with at least two domains, wherein the first domain is capable of binding CD3 and the second domain is capable of binding to a cancer cell. Also disclosed herein are methods of treating cancer in a subject, comprising: providing a composition comprising a polypeptide with at least two domains, wherein the first domain is capable of binding CD3 and the second domain is capable of binding to a cancer cell; and treating the cancer by administering a therapeutically effective dosage of the composition to the subject.