BACKGROUND: Studies demonstrating that human glandular kallikrein (hK2) is increased in prostate cancer patients have prompted speculation that this marker may of use in addition to prostate-specific antigen (PSA). METHODS: An ultrasensitive hK2 sandwich immunoassay was developed, and its detection limit, cross-reactivity, analytical recovery, precision, and linearity of dilution were evaluated. hK2 was measured in seminal plasma and sera from healthy males, females, and prostatectomized patients. RESULTS: Our assay has an excellent detection limit (6 ng/L) and precision (>90%). Recovery studies indicated that hK2 binds to serum protease inhibitors. All sera from healthy males had measurable hK2 concentrations (median, 402 ng/L). Almost all female sera had undetectable hK2. Serum hK2 and PSA in males correlated positively (r = 0.44), but hK2 was present at concentrations approximately 2. 5-fold lower than PSA. The PSA/hK2 ratio in male sera was 0.1-34, with a median of 2.6. In seminal plasma, this ratio was 100-500. More than 94% of immunoreactive hK2 in serum was in the free form ( approximately 30 kDa); traces of hK2 complexed to alpha1-antichymotrypsin were present. CONCLUSIONS: The limit of detection of the method for hK2 measurement described here ( approximately 20-fold lower than any other reported assay for hK2) allows the generation of new clinical information. When combined with a previously described method for PSA measurement that has no cross-reactivity from hK2, this methods allows the relative proportions of hK2 and PSA in biological fluids to be measured.
BACKGROUND: Studies demonstrating that human glandular kallikrein (hK2) is increased in prostate cancerpatients have prompted speculation that this marker may of use in addition to prostate-specific antigen (PSA). METHODS: An ultrasensitive hK2 sandwich immunoassay was developed, and its detection limit, cross-reactivity, analytical recovery, precision, and linearity of dilution were evaluated. hK2 was measured in seminal plasma and sera from healthy males, females, and prostatectomized patients. RESULTS: Our assay has an excellent detection limit (6 ng/L) and precision (>90%). Recovery studies indicated that hK2 binds to serum protease inhibitors. All sera from healthy males had measurable hK2 concentrations (median, 402 ng/L). Almost all female sera had undetectable hK2. Serum hK2 and PSA in males correlated positively (r = 0.44), but hK2 was present at concentrations approximately 2. 5-fold lower than PSA. The PSA/hK2 ratio in male sera was 0.1-34, with a median of 2.6. In seminal plasma, this ratio was 100-500. More than 94% of immunoreactive hK2 in serum was in the free form ( approximately 30 kDa); traces of hK2 complexed to alpha1-antichymotrypsin were present. CONCLUSIONS: The limit of detection of the method for hK2 measurement described here ( approximately 20-fold lower than any other reported assay for hK2) allows the generation of new clinical information. When combined with a previously described method for PSA measurement that has no cross-reactivity from hK2, this methods allows the relative proportions of hK2 and PSA in biological fluids to be measured.
Authors: M H Black; A Magklara; C Obiezu; M A Levesque; D J Sutherland; D J Tindall; C Y Young; E R Sauter; E P Diamandis Journal: Br J Cancer Date: 2000-01 Impact factor: 7.640