The role of molecular forms of prostate-specific antigen (PSA or hK3) and of human glandular kallikrein 2 (hK2) in the diagnosis and monitoring of prostate cancer and in extra-prostatic disease

Prostate-specific antigen (PSA or hK3) is a glandular kallikrein with abund ant expression in the prostate that is widely used to detect and monitor pr ostate cancer (PCa), although the serum level is frequently elevated also i n benign and inflammatory prostatic diseases. PSA testing is useful for ear ly detection of localized PCa and for the detection of disease recurrence a fter treatment. However, PSA has failed to accurately estimate cancer volum e and preoperative staging. There is no PSA level in serum that definitivel y distinguishes men with benign conditions from those with prostate cancer, although PCa is rare in men with PSA levels in serum < 2.0 ng/ml. This pro mpted searches for enhancing parameters to combine with PSA testing, such a s PSA density, PSA velocity, and age-specific reference ranges. Due to the protease structure, PSA occurs in different molecular forms in serum and th eir concentrations vary according to the type of prostatic disease. Human g landular kallikrein 2 (hK2) is very similar to PSA, but expressed at higher levels in prostate adenocarcinoma than in nor-Mal prostate epithelium. Blo od testing for hK2 combined with different PSA forms improves discriminatio n of men with benign prostatic disease from those with prostate cancer. Man y data have also been reported on the extra-prostatic expression of both PS A and hK2, and it is now believed that they may both have functions in tiss ues outside the prostate.