FOLH1 and prostate cancer: Since urea-based inhibitors of PSMA clear rapidly from the circulation and since only low levels of physiological PSMA expression were detected in a few organs like the brain, kidney, salivary gland and small intestine [7,9,10,11] PSMA represents an ideal biological target for high quality PET imaging of prostate cancer [12,13,14,15,16,17].