Rittenhouse, Harry G.

AbstractBackground: Human kallikrein 2 (hK2) shares 80% sequence identity with prostate-specific antigen (PSA). Because both hK2 and hK2-α1-antichymotrypsin (hK2-ACT) complexes have been identified in patient sera, we devised an immunoassay for total hK2 [(thK2); hK2 and hK2-ACT] and evaluated it in healthy subjects and patients with prostate disease.Methods: We developed monoclonal antibodies (mAbs) with high specificity for hK2 and hK2-ACT and minimal cross-reactivity to PSA. Using these mAbs, a sandwich assay was developed and its specificity for forms of hK2 was assessed. Serum samples (n = 1035) from healthy volunteers, patients with increased PSA, and men who had undergone radical prostatectomy were assayed for thK2. We also measured thK2 in samples before and after storage under common laboratory conditions.Results: The minimum detectable concentration in the thK2 assay was 0.008 μg/L, and PSA cross-reactivity was <0.001%. The assay detected prohK2 and three different hK2–serum protease complexes. The median serum concentration of thK2 in control samples (0.013 μg/L) was significantly lower than the median in samples from patients with increased PSA concentrations (0.085 μg/L). Immunoreactive hK2 changed little in samples stored for up to 1 month at −70 °C.Conclusions: The thK2 assay recognizes all forms of hK2 that have been found in bodily fluids to date.

AbstractBackground: 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.

AbstractBackground: Updated National Academy of Clinical Biochemistry (NACB) Laboratory Medicine Practice Guidelines for the use of tumor markers in the clinic have been developed.Methods: Published reports relevant to use of tumor markers for 5 cancer sites—testicular, prostate, colorectal, breast, and ovarian—were critically reviewed.Results: For testicular cancer, α-fetoprotein, human chorionic gonadotropin, and lactate dehydrogenase are recommended for diagnosis/case finding, staging, prognosis determination, recurrence detection, and therapy monitoring. α-Fetoprotein is also recommended for differential diagnosis of nonseminomatous and seminomatous germ cell tumors. Prostate-specific antigen (PSA) is not recommended for prostate cancer screening, but may be used for detecting disease recurrence and monitoring therapy. Free PSA measurement data are useful for distinguishing malignant from benign prostatic disease when total PSA is <10 μg/L. In colorectal cancer, carcinoembryonic antigen is recommended (with some caveats) for prognosis determination, postoperative surveillance, and therapy monitoring in advanced disease. Fecal occult blood testing may be used for screening asymptomatic adults 50 years or older. For breast cancer, estrogen and progesterone receptors are mandatory for predicting response to hormone therapy, human epidermal growth factor receptor-2 measurement is mandatory for predicting response to trastuzumab, and urokinase plasminogen activator/plasminogen activator inhibitor 1 may be used for determining prognosis in lymph node–negative patients. CA15-3/BR27–29 or carcinoembryonic antigen may be used for therapy monitoring in advanced disease. CA125 is recommended (with transvaginal ultrasound) for early detection of ovarian cancer in women at high risk for this disease. CA125 is also recommended for differential diagnosis of suspicious pelvic masses in postmenopausal women, as well as for detection of recurrence, monitoring of therapy, and determination of prognosis in women with ovarian cancer.Conclusions: Implementation of these recommendations should encourage optimal use of tumor markers.