Use of human glandular kallikrein 2 for the detection of prostate cancer: Preliminary analysis

Objectives, Human glandular kallikrein 2 (hK2) and prostate-specific antige n (PSA) are members of a multigene family of serine proteases that share ap proximately 80% sequence homology. Both are expressed in the prostate epith elium, are under androgen regulation, are present in serum and seminal flui d, and can form complexes with endogenous protease inhibitors (eg, alpha(2) -macroglobulin and alpha(1)-antichymotrypsin). Differences in immunohistoch emistry and substrate specificity suggest hK2 may provide unique informatio n for early detection and characterization of prostate cancer. Methods. Nine hundred thirty-seven archived serum samples from men treated at two academic institutions were studied. All men underwent biopsy, had a histologically confirmed diagnosis of cancer or noncancer, and a total PSA level greater than 2 ng/mL. Samples were tested in Hybritech's Tandem-R PSA and Tandem-R free PSA (fPSA) assays and a research prototype assay for tot al hK2 (thK2). Results. The thK2/fPSA ratio provided additional specificity for cancer det ection over PSA and the percentage of fPSA (%fPSA). A model for cancer dete ction using %fPSA and the thK2/fPSA ratio when PSA is 2 to 4 ng/mL is propo sed that would identify as many as 40% of the cancers and would require bio psy in only 16.5% of the men in this PSA range. Conclusions. In this study, %fPSA and thK2/fPSA provided unique information for prostate cancer detection and increased the specificity of cancer dete ction. UROLOGY 54: 839-845, 1999. (C) 1999, Elsevier Science Inc.