Improved cancer therapies are provided and include methods for inhibiting growth of tumor cells in an individual by administering to the individual a polynucleotide encoding a protein that contains an immunoglobulin Fc and an antagonist peptide of a receptor expressed by tumor cells, and administering a chemotherapeutic agent to the individual, such that the growth of the tumor cells and/or metastasis of cancer cells is synergistically inhibited. Approaches are also provided for improving cancer therapies that include adoptive immunotherapies by using the polynucleotides to enhance tumor infiltration by immune cells.
