Highly Sensitive Automated Chemiluminometric Assay for Measuring Free Human Glandular Kallikrein-2

Abstract

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 α1-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® 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.

Serum human glandular kallikrein 2 (hK2) for distinguishing stage and grade of prostate cancer

“…So far, no commercially available hK2 assays exist and there is not universally accepted calibrator for hK2 like there is for PSA. There have been three hK2 assays available to date: (i) the assay in the present study; 34 (ii) the Beckman Coulter total hK2 assay; 40 and (iii) the Turku hK2 assay. 41 The hK2 assay used in this study measured about 1.5-fold higher concentrations when compared with the Beckman Coulter hK2 research assay (obtained on 29 samples, data not shown).…”

The diagnostic and prognostic utility of prostate-specific antigen for diseases of the breast

“…While the total PSA level alone is neither sensitive nor specific enough for the early diagnosis of prostate cancer, the ratio of free to total PSA may improve both sensitivity and specificity [32]. The application of hK2 as an additional serum marker for the detection, prognosis, and monitoring of prostate cancer patients has recently emerged [33][34][35][36][37]. The measurement of both kallikreins introduces the possibility of multiple parameter testing for prostate cancer.…”

Clinical utility of human glandular kallikrein 2 within a neural network for prostate cancer detection

“…There are no commercially available hK2 assays, and there is no universally accepted calibrator for hK2 as there is for PSA. Three hK2 assays have been used for most hK2 testing to date: the assay in the present study [31]; the Beckman Coulter total hK2 assay [35]; and the Turku hK2 assay [36]. The present assay measured about 1.5 times higher hK2 concentrations than the Beckman Coulter assay.…”