We describe a solid-phase radioimmunometric sandwich assay for a new tumor marker defined by a monoclonal antibody (19-9). This antibody reacts with a carbohydrate antigenic determinant (CA 19-9) found at low concentrations in sera from healthy individuals but frequently increased in sera from patients with adenocarcinomas. The assay is sensitive and simple to perform. It requires duplicate 100-microL samples and may be performed in 6 h. The concentration of CA 19-9 in samples is determined by reference to a standard curve, which is essentially linear from 0 to 120 arbitrary units/mL. The average CV is approximately 10% in the range of 5.8 to 120 units/mL. The minimum detectable dose is 1.4 units/mL and analytical recovery of CA 19-9 is 97.6 to 100.6%. The average concentration of CA 19-9 in sera from 1020 healthy individuals was 8.4 (SD 7.4) units/mL; only 0.6% of such sera had concentrations greater than 37 units/mL. The assay has high specificity (98.5%), even among patients with benign diseases, and has high sensitivity (up to 79%) for patients with gastrointestinal adenocarcinomas, especially those of the pancreas.
Endogenous expression of the murine leukemia virus (MuLV) genome has been studied in a number of strains of mice. Expression of the major envelope glycoprotein, gp70, is restricted to certain anatomical sites and cell types, prominent among which are lymphoid and epithelial cells. On a quantitative basis, the major site of gp70 expression is the male genital tract. During development, gp70 first appears in the hematopoietic liver of 14-day-old embryos and by day 18, it is already expressed at anatomical sites similar to those of the adult. In toto, these results show that control of expression of the MuLV genome in adult and developing mice is linked to differentiation.
More than 1,600 coded sera obtained from blood donors and the NCI/Mayo Clinic Serum Bank were analyzed with an improved immunoradiometric assay for the carbohydrate antigenic determinant, CA 19-9. Results indicated that CA 19-9 is elevated in a large fraction of sera (67%) from patients with advanced adenocarcinomas of the upper gastrointestinal (GI) tract, including those with pancreatic, hepatobiliary and gastric carcinomas. Several of these sera had CA 19-9 exceeding 300,000 U/ml. A smaller fraction (18%) of patients with carcinomas of the large bowel had elevated serum CA 19-9 levels, the majority among patients with metastatic disease. In contrast, none of the healthy donors from the serum bank and only 4 of 1,023 of the blood donor specimens (0.4%) had CA 19-9 levels greater than or equal to 40 U/ml. Three of 235 sera (1.3%) from benign disease patients had levels of CA 19-9 in excess of 40 U/ml. These data suggest that the improved CA 19-9 immunoradiometric assay may have clinical utility as a diagnostic adjunct for adenocarcinoma of the upper GI tract and that the assay also may have some value in monitoring patients with advancing colorectal carcinoma, particularly in combination with CEA determinations. Rigorous prospective clinical trials will be necessary to verify these hypotheses.
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