DKK1-DNA vaccines induce CD4⁺ and CD8⁺ T-cell responses. Mice (5 per group) were vaccinated thrice with PBS, vector control, DKK1 DNA, or DKK1 DNA plus CpG, followed by challenge with MOPC-21 cells. T cells were isolated from spleens and tumors after 2 weeks of tumor challenge, restimulated by the irradiated tumor cells, and analyzed by flow cytometry. Shown are percentages of IFN-γ– and IL-4–expressing CD4⁺ (A) and CD8⁺ (B) T cells in the spleens of mice receiving different treatments. Also shown are the percentages of CD4⁺Foxp3⁺ Treg cells (C) and CD3⁺ and CD8⁺ T cells (D) in the spleens (top panels) and tumors (bottom panels) of mice receiving different treatments. Representative results of 1 of 2 independent experiments performed are shown. *P < .05; **P < .01, compared with PBS controls.