Highly sensitive automated chemiluminometric assay for measuring free human glandular kallikrein-2.
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.


CONCLUSIONS
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.
Klee
G G
GG
Departments of Laboratory Medicine and Pathology, Epidemiology, and Urology Research, Mayo Clinic and Mayo Foundation, 200 First Street SW, Rochester, MN 55905, USA. klee.george@mayo.edu
Goodmanson
M K
MK
Jacobsen
S J
SJ
Young
C Y
CY
Finlay
J A
JA
Rittenhouse
H G
HG
Wolfert
R L
RL
Tindall
D J
DJ
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000911:Antibodies, Monoclonal; D003429:Cross Reactions; D005260:Female; D006801:Humans; D007118:Immunoassay; D007610:Kallikreins / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D008297:Male; D051379:Mice; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood / Q000378:metabolism; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000097:blood / Q000601:surgery; D011485:Protein Binding; D011994:Recombinant Proteins / Q000276:immunology; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D020840:Tissue Kallikreins; D000514:alpha 1-Antichymotrypsin / Q000378:metabolism
D000911:Antibodies, Monoclonal; D011994:Recombinant Proteins; D000514:alpha 1-Antichymotrypsin; D007610:Kallikreins; D020840:Tissue Kallikreins; D017430:Prostate-Specific Antigen