DEVELOPMENT OF HIGHLY SENSITIVE IMMUNOASSAYS TO MEASURE HUMAN CHORIONIC-GONADOTROPIN, ITS BETA-SUBUNIT, AND BETA-CORE FRAGMENT IN THE URINE - APPLICATION TO MALIGNANCIES

  • 1 March 1988
    • journal article
    • research article
    • Vol. 48  (5) , 1361-1366
Abstract
A variety of malignancies have been associated with the presence of human chorionic gonadotropin, hCG, its subunits, and fragments of its .beta.-subunit in blood and urine. The usefulness of these hCG-related tumor markers in nontrophoblastic malignancies has been inhibited by inadequate assay techniques. In order to achieve the required sensitivity and specificity, concentration steps and other procedures to remove cross-reacting human luteinizing hormone were necessary. In addition, the coexistence of a fragment of the hCG-.beta. or .beta. human luteinizing hormone subunit contributes to significant errors of measurement in urine. The importance of the hCG-.beta. fragment as a potential tumor marker has been recognized previously but no method was available to measure this antigen readily. We report here the development of a series of radioimmunometric, two-site assays which will accurately measure hCG, hCG-.beta. subunit, and the .beta.-subunit fragment directly in small volumes of unprocessed urine. These assays are highly specific, extremely sensitive, and not labor intensive since they employ microtiter plate procedures. Application of these assays to urine samples from patients with gynecological malignancies indicated that over 50% of all patients tested excreted the hCG-.beta. fragment in their urine. Also, this fragment comprised more than 50% of the moles of hCG immunoreactive components present in the specimens that were positive for hCG. This cancer marker is also demonstrable in trophoblastic malignant states such as choriocarcinoma in which the low molecular weight fragment can also be visualized directly by immunoblotting procedures. We conclude that a search for hCG immunoreactivity in the urine of patients with malignancies will be improved by the inclusion of accurate measurements of the prominent quantities of the .beta. fragment excreted by these individuals.