| Research Abstract |
An Mr 110,000 antigen (Mr 110,000 Ag) was initially described in human gastric carcinoma cells by tis cross-reactivity with monoclonal antibodies (MAbs) to carcinoembryonic antigen (CEA). We describe the molecular cloning and sequence analysis of a full-length cDNA that encodes for the entire Mr 110,000 molecule. The sequence result obtained was identical to that for the Mr 110,000 antigen reported by Shimada et al. The Mr 110,000 Ag was purified by a combination of immunoaffinity chromatography and gel filtration. An MAb specific for the Mr 110,000 antigen was generated using the purified antigen as immunogen.
Serum Mr 110,000 Ag levels were estimated by a sandwich-type solid-phase enzyme immunoassay (new EIA) in which an CEA-cross-reactive MAb immobilized on 96-well polyvinyl chloride microtier plates was used as the catcher and another MAb specific for the Mr 110,000 Ag was biotinylated and used as the tracer. When frequency of elevated Mr 110,000 Ag levels in sera from various diseases was compared, it is evident that the total positive rate for malignant disease showed a definite increase with new EIA compared to that of EIA for CEA.In digestive tract malignancies, especially gastric cancer, prominently increased positive rates were observed with new EIA,whereas there was only slight increase for breast or ovarian cancer. In sera from normal individuals, new EIA gave a slightly decreased false positive rate as compared with EIA for CEA.Consequently, the diagnostic efficiency revealed an improvement with new EIA for the Mr 110,000 Ag. However, new EIA deserves further evaluation, especially among longitudinal collected serum samples from cancer patients, to determine how well antigen concentration correlates with clinical course.
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