Kallikreins are a subgroup of serine proteases having diverse physiological functions. Growing evidence suggests that many kallikreins are implicated in carcinogenesis and some have potential as novel cancer and other disease biomarkers. kallikrein-related peptidase 3,which is also called PSA (prostate-specific antigen) in the clinical setting,is useful in the diagnosis and monitoring of prostatic carcinoma. KLK3 has 5 isoforms produced by alternative splicing.