OR51E2 and prostate cancer: This is considered to be a major obstacle in the induction of TAA-specific T cells capable of eradicating tumors in vivo. However, in our study, although PSGR is expressed in normal prostate tissue, immune tolerance against PSGR can be broken, since T cell responses against PSGR-derived epitopes were frequently detectable in PBMCs from either healthy subjects or prostate cancer patients.