A polypeptide is disclosed that binds tumor-associated antigens (TAA) on the surface of cancer cells and a NKG2D receptor. The NKG2D receptor is expressed on the surfaces of killer cells such as natural killer cells, T cells, natural killer T cells, and gamma delta T cells. In some cases, the TAA is CS-1 or EGFRvIII. Also disclosed are polynucleotides encoding the disclosed polypeptides, vectors comprising the disclosed polynucleotides, and host cells comprising the disclosed vectors. Also disclosed are bivalent antibodies comprising the disclosed polypeptides. Also disclosed are pharmaceutical compositions comprising the disclosed antibodies. Also disclosed are methods of treating cancer in a subject using the disclosed bi-specific antibodies.
