Cloning of cDNA and establishment of an assay system for Mr 110,000 Ag

一种Mr 110,000抗原（Mr 110,000 Ag）最初在人胃癌细胞中与癌胚抗原（CEA）单克隆抗体（mab）交叉反应。我们描述了编码整个Mr 110,000分子的全长cDNA的分子克隆和序列分析。所获得的序列结果与Shimada等报道的Mr 110,000抗原的序列结果一致。采用免疫亲和层析和凝胶过滤相结合的方法纯化Mr 110,000 Ag。用纯化后的抗原作为免疫原，制备了Mr 110,000抗原特异性的单克隆抗体。采用三明治型固相酶免疫分析法（new EIA）估计血清Mr 110,000 Ag水平，其中固定化在96孔聚氯乙烯微层板上的cea -交叉反应单抗作为捕集剂，另一种Mr 110,000 Ag特异性单抗被生物素化并用作示踪剂。当比较不同疾病血清Mr 110,000 Ag水平升高的频率时，很明显，与CEA的EIA相比，新EIA对恶性疾病的总阳性率明显增加。在消化道恶性肿瘤中，特别是胃癌，新EIA的阳性率显著增加，而乳腺癌和卵巢癌的阳性率仅略有增加。在正常人群的血清中，新EIA对CEA的假阳性率略低于EIA。因此，新的EIA对Mr 11万Ag的诊断效率有所提高。然而，新的EIA值得进一步评估，特别是在癌症患者的纵向血清样本中，以确定抗原浓度与临床病程的相关性。

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.