KLK4 and prostate carcinoma: Prostate-specific antigen (PSA), also known as human kallikrein 3 (hK3), according to the approved new nomenclature of the human kallikrein family (Diamandis et al, 2000a), is used for early detection and monitoring of prostate cancer (Bilhartz et al, 1991; Oesterling, 1991; Diamandis et al, 2000b).