A DNA-based combined formulation composed of INO-5150, DNA plasmids encoding the tumor-associated antigens (TAAs) prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA), and INO-9012, a plasmid DNA vaccine encoding the immune activator and pro-inflammatory cytokine human interleukin-12 (IL-12), with potential immunoactivating and antineoplastic activities. Upon intramuscular delivery of INO-5151 and electroporation of the PSA/PSMA DNA plasmid INO-5150, PSA and PSMA are translated in cells and elicit a cytotoxic T-lymphocyte (CTL) response against cancer cells expressing PSA and PSMA, resulting in tumor cell lysis. Upon electroporation of the DNA plasmid encoding IL-12 INO-9012, IL-12 is translated in cells and the expressed IL-12 activates the immune system by promoting the activation of natural killer cells (NK cells), inducing secretion of interferon-gamma (IFN-g) and promoting CTL responses against tumor cells. This boosts the immune response and results in increased CTL-mediated tumor cell death as compared with the administration of INO-5150 alone. PSA and PSMA are overexpressed on a variety of cancer cell types.