Immunization With WT1-derived Peptides by Tattooing Inhibits the Growth of TRAMP-C2 Prostate Tumor in Mice

The expression of the transcription factor encoded by the Wilms tumor gene 1 (WT1) is associated with a variety of human cancers. WT1 protein has been reported to serve as a target antigen for tumor-specific immune responses. We observed that the immunization of mice with peptide vaccines derived from WT1 in a mixture with the CpG adjuvant (ODN 1826) by tattoo administration was superior to subcutaneous delivery of the peptides in combination with CpG formulated with the mineral oil adjuvant or a DNA vaccine or a recombinant vaccinia virus vaccine expressing the truncated WT1 protein. Tattooing with the WT1(122-140) and WT1(126-134) peptide elicited the response of WT1-specific interferon-gamma-producing T cells. Peptide vaccine administered with a tattoo device had an antitumor effect on the growth of the prostate tumor cell line TRAMP-C2, provided that the transforming growth factor-beta produced by tumor cells was neutralized by anti-TGF beta monoclonal antibody. The treatment of the tumor-bearing mice with 5-azadeoxycytidine or poly IC did not work in synergy with the peptide vaccine.