BACKGROUND: Human glandular kallikrein (hK2) is a serine protease that has 79% amino acid identity with prostate-specific antigen (PSA). Both free hK2 and hK2 complexed to alpha1-antichymotrypsin (ACT) are present in the blood in low concentrations. We wished to measure hK2 in serum with limited contribution from hK2-ACT for the results. METHODS: We developed an automated assay for hK2 with use of a select pair of monoclonal antibodies. The prototype assay was implemented on a Beckman Coulter ACCESS(R) analyzer. RESULTS: The detection limit of the assay was 1.5 ng/L, the "functional sensitivity" (day-to-day CV <15%) was <4 ng/L, cross-reactivity with PSA and PSA-ACT was negligible, and cross-reactivity with hK2-ACT was 2%. After surgical removal of prostate glands, serum hK2 was <7 ng/L and was <15 ng/L in most healthy women. The median serum concentration of hK2 in healthy men without prostate cancer was 26 ng/L. The median concentration of hK2 was 72 ng/L for men having prostate cancer with lower Gleason scores compared with 116 ng/L for men with more advanced cancer. The concentration of hK2 correlated weakly with PSA, with the mean hK2 concentrations generally 30- to 80-fold lower than PSA concentrations. CONCLUSION: The availability of a robust, high sensitivity automated assay for hK2 should facilitate further investigations of the role of hK2 measurements in the management of patients with prostate disease.
BACKGROUND:Human glandular kallikrein (hK2) is a serine protease that has 79% amino acid identity with prostate-specific antigen (PSA). Both free hK2 and hK2 complexed to alpha1-antichymotrypsin (ACT) are present in the blood in low concentrations. We wished to measure hK2 in serum with limited contribution from hK2-ACT for the results. METHODS: We developed an automated assay for hK2 with use of a select pair of monoclonal antibodies. The prototype assay was implemented on a Beckman Coulter ACCESS(R) analyzer. RESULTS: The detection limit of the assay was 1.5 ng/L, the "functional sensitivity" (day-to-day CV <15%) was <4 ng/L, cross-reactivity with PSA and PSA-ACT was negligible, and cross-reactivity with hK2-ACT was 2%. After surgical removal of prostate glands, serum hK2 was <7 ng/L and was <15 ng/L in most healthy women. The median serum concentration of hK2 in healthy men without prostate cancer was 26 ng/L. The median concentration of hK2 was 72 ng/L for men having prostate cancer with lower Gleason scores compared with 116 ng/L for men with more advanced cancer. The concentration of hK2 correlated weakly with PSA, with the mean hK2 concentrations generally 30- to 80-fold lower than PSA concentrations. CONCLUSION: The availability of a robust, high sensitivity automated assay for hK2 should facilitate further investigations of the role of hK2 measurements in the management of patients with prostate disease.
Authors: Daniel E Spratt; Michael J Evans; Brian J Davis; Michael G Doran; Man Xia Lee; Neel Shah; John Wongvipat; Kathryn E Carnazza; George G Klee; William Polkinghorn; Donald J Tindall; Jason S Lewis; Charles L Sawyers Journal: Cancer Res Date: 2015-10-02 Impact factor: 12.701