Data from Recognition of Prostate and Melanoma Tumor Cells by Six-Transmembrane Epithelial Antigen of Prostate–Specific Helper T Lymphocytes in a Human Leukocyte Antigen Class II–Restricted Manner

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<div>Abstract<p>The six-transmembrane epithelial antigen of prostate (STEAP) protein is an attractive candidate for T cell–based immunotherapy because it is overexpressed in prostate cancer and various other tumor types. Several peptide epitopes capable of stimulating CTLs that killed STEAP-expressing tumor cells have been described. Our goal was the identification of helper T lymphocyte (HTL) epitopes of STEAP for the optimization of T cell–based immunotherapies against STEAP-expressing malignancies. Candidate HTL epitopes for STEAP were predicted using <i>in silico</i> algorithms for HLA class II–binding peptides and were tested for their ability to elicit HTL responses by <i>in vitro</i> peptide vaccination of CD4 T lymphocytes from healthy individuals and prostate cancer patients. Two peptides (STEAP<sub>102–116</sub> and STEAP<sub>192–206</sub>) were effective in stimulating <i>in vitro</i> antitumor HTL responses in both normal individuals and prostate cancer patients. Notably, both STEAP HTL peptides behaved as promiscuous T-cell epitopes because they stimulated T cells in the context of more than one MHC class II allele. These newly described STEAP HTL epitopes could be of value for the design and optimization of T cell–based immunotherapy against STEAP-expressing tumors. [Cancer Res 2007;67(11):5498–504]</p></div>