Provided are compositions and methods for inhibiting cell growth. The cells that are targeted by the compositions and methods of the invention express an antigen, a mimotope of the antigen, or a CXCR4 chemokine receptor. The method entails administering to an individual a polynucleotide encoding an immunoglobulin Fc and an antigen expressed by the cells or a mimotope of the antigen. The method also involves administering to the individual a composition which contains a polynucleotide encoding an immunoglobulin Fc and an antagonist peptide of a CXCR4 chemokine receptor expressed by the cells. Also provided are proteins encoded by the polynucleotides.
