Bunworasate U, Voravud N
Department of Medicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
J Med Assoc Thai. 1995 May;78(5):255-70.
Efforts to find the ideal tumor marker, together with the advanced knowledge of the carbohydrate expression by cancer and the development of monoclonal antibody technology have facilitated the generation of many new tests used in clinical oncology. CA 50, a novel cancer-associated carbohydrate marker, is detected by the C 50 antibody that has been obtained by immunization of mice with a human colorectal adenocarcinoma cell line. This antibody that defines CA 50 reacts with both the afucosyl form of sialylated Lewis(a) carbohydrate moiety and sialylated Lewis(a) moiety which is also the antigenic epitope in the CA 19-9 assay. CA 50 is not organ-specific and its elevated levels in serum can be observed in a variety of malignancies, especially gastrointestinal cancers. In contrast to CA 19-9, high CA 50 levels can also be seen in malignant tumors outside the digestive tract. The expectation, that CA 50 might be positive in the Lewis negative patients who cannot synthesize CA 19-9, is supported by the histoimmunologic study. However, in serum determination close correlation between CA 50 and CA 19-9 has been observed even in patients who have Lewis negative phenotype. In clinical application, CA 50 is marginally beneficial for the diagnosis, but very useful for the follow-up of patients with pancreatic cancers. It gives results rather similar to CA 19-9. Moderately high serum levels of CA 50 can also be seen in benign hepatobiliary diseases, especially in jaundice cases. Therefore, this should be considered in order to obtain the most advantage of the marker. For other gastrointestinal cancers, CA 50 in combination with other previously defined markers may give additional information for the evaluation of some patients with colorectal, biliary, or gastric cancers. At present, there are many new emerging tumor markers used in clinical oncology. Increasing our knowledge about these markers, their capabilities and limitations will enable us to use them effectively in the evaluation of cancer patients.
寻找理想肿瘤标志物的努力，以及对癌症碳水化合物表达的深入了解和单克隆抗体技术的发展，推动了临床肿瘤学中许多新检测方法的产生。CA 50是一种新型的癌症相关碳水化合物标志物，通过用人结肠直肠腺癌细胞系免疫小鼠获得的C 50抗体进行检测。定义CA 50的这种抗体与唾液酸化Lewis(a)碳水化合物部分的去岩藻糖基形式以及唾液酸化Lewis(a)部分发生反应，而后者也是CA 19-9检测中的抗原表位。CA 50并非器官特异性的，在多种恶性肿瘤中，尤其是胃肠道癌症患者的血清中可观察到其水平升高。与CA 19-9不同，在消化道外的恶性肿瘤中也可发现高CA 50水平。组织免疫研究支持了这样一种期望，即CA 50在无法合成CA 19-9的Lewis阴性患者中可能呈阳性。然而，在血清检测中，即使在具有Lewis阴性表型的患者中，也观察到CA 50与CA 19-9之间存在密切相关性。在临床应用中，CA 50对诊断的帮助不大，但对胰腺癌患者的随访非常有用。其结果与CA 19-9相当相似。在良性肝胆疾病中，尤其是黄疸病例中，也可观察到CA 50血清水平中度升高。因此，为了充分利用该标志物，应考虑到这一点。对于其他胃肠道癌症，CA 50与其他先前确定的标志物联合使用，可能会为评估一些结直肠癌、胆管癌或胃癌患者提供更多信息。目前，临床肿瘤学中使用了许多新出现的肿瘤标志物。增加我们对这些标志物及其能力和局限性的了解，将使我们能够在癌症患者的评估中有效地使用它们。
