Prostate-specific membrane antigen (PSMA), a type II transmembrane protein on the surface of cancer cells, is considered to be the most interesting antigen in prostate cancer, since it is overexpressed in high-grade tumors, metastases, and hormone-resistant tumors with low concomitant expression (100 to 1,000 times less) in normal tissues (179). Here, FOLH1 is linked to cancer.