Development of Sensitive Immunoassays for Free and Total Human Glandular Kallikrein 2

Abstract

Background: Free and total human kallikrein 2 (hK2) might improve the discrimination between prostate cancer and benign prostatic hyperplasia. Concentrations of hK2 are 100-fold lower than concentrations of prostatespecific antigen (PSA); therefore, an hK2 assay must have a low detection limit and good specificity. Methods: PSA-and hK2-specific monoclonal antibodies were used in solid-phase, two-site immunofluorometric assays to detect free and total hK2. The total hK2 assay used PSA-specific antibodies to block nonspecific signal. The capture antibody of the free hK2 assay did not cross-react with PSA. To determine the hK2 concentrations in the male bloodstream, total hK2 was measured in a control group consisting of 426 noncharacterized serum samples. Free and total hK2 were measured in plasma from 103 patients with confirmed prostate cancer. Results: All 426 males in the control group had a total hK2 concentration above the detection limit of 0.0008 g/L. The median total hK2 concentration was 0.022 g/L (range, 0.0015-0.37 g/L). hK2 concentrations were 0.1-58% of total PSA (median, 3.6%). hK2 concentrations were similar in men 41-50 and 51-60 years of age. The ratio of hK2 to PSA steadily decreased from 5-30% at PSA <1 g/L to 1-2% at higher PSA concentrations. In 103 patients with prostate cancer, the median hK2 concentration in plasma was 0.079 g/L (range, 0.0015-16.2 g/L). The median free hK2 concentration was 0.070 (range, 0.005-12.2) g/L. The proportion of free to total hK2 varied from 17% to 131% (mean, 85%).

Comparison of Free and Total Forms of Serum Human Kallikrein 2 and Prostate-Specific Antigen for Prediction of Locally Advanced and Recurrent Prostate Cancer

“…Analysis of our study population, a reasonably representative cohort of 867 men from a contemporary population treated with radical prostatectomy for clinically localized PCa at a single institution, included fPSA and a recently published method for fhK2 detection (24 ). Previous studies indicated that a low ratio of fPSA to tPSA (%fPSA) is linked to advanced prostate pathology.…”

“…Others, however, were not able to confirm these findings. The ratio of fhK2 to thK2 (%fhK2) has been previously measured in a set of 103 patients with PCa, in whom it ranged from 17% to 131% (mean, 81%) (24 ). However, no study has ever evaluated the clinical relevance of serum fhK2.…”

“…The percentage of fPSA (%fPSA) was calculated as %fPSA ϭ fPSA/tPSA ⅐ 100. thK2 and fhK2. PSA-and hK2-specific monoclonal antibodies were used in solid-phase, 2-site immunofluorometric assays to detect fhK2 and thK2 (24 ). The thK2 assay used PSA-specific antibodies to block nonspecific signals.…”

Kallikrein-related peptidases (KLKs): a gene family of novel cancer biomarkers

“…A very recent study established, also, a reference interval for KLK6 serum levels in adults (145) . Moreover, Vaisanen et al developed a sensitive immunoassay with good specifi city for the accurate determination of free and total human kallikrein 2 (KLK2) concentration in the male bloodstream, as this might improve the discrimination between prostate cancer and benign prostatic hyperplasia (146) . tPSA and fPSA were also measured in the blood serum of patients with prostate cancer or BPH, using immunofl uorometric techniques (147) .…”

Real-time quantitative RT-PCR assessment of PIM-1 and hK2 mRNA expression in benign prostate hyperplasia and prostate cancer

“…Recently, when differentiate expression of PIM-1 in normal prostate and PCa was analyzed by gene chip analysis, over-expression of PIM-1 in PCa has been demonstrated [5,6]. Human glandular kallikrein (hK2) is an androgen-regulated protein that has high identity with prostate-specific antigen (PSA) and is expressed almost exclusively in prostatic epithelial cells [7,8]. Although the expression of PSA has been found to be reduced in higher grade and presumably more biologically active disease, the expression of hK2 has been found to increase gradually from benign epithelium to prostatic intraepithelial neoplasia and to prostate cancer.…”