Tissue specificity of Carcinoembryonic antigen

癌胚抗原（CEA）是一种癌胚细胞表面糖蛋白。由于CEA在肿瘤中的高表达和分泌到血清中，其已被广泛用作血清肿瘤标志物。为了研究CEA的组织特异性，我们使用蛋白质组学策略研究了CEACAM家族成员的表达模式和来自几种癌细胞系的CEA分子上的N-糖基化模式。我们鉴定了CEA上新的N-糖基化位点，进一步的精确研究表明，N-糖基化模式在各种癌细胞系中是不同的。此外，在胃肠道癌细胞系中鉴定了两种新的CEA剪接变体。这些转录本在正常组织中不表达。源自新剪接变体的CEA蛋白同种型也在癌细胞系中表达，并且这些蛋白同种型分泌到培养基中。我们还发现CEACAM 4的表达是甲状腺髓样癌细胞系所独有的。

Carcinoembryonic antigen (CEA) is an oncofetal cell surface glycoprotein. Because of its high expression in tumors and secretion to serum, CEA has been widely used as a serum tumor marker. To investigate the tissue specificity of CEA, we examined the expression patterns of CEACAM family members and the N-glycosylation patterns on CEA molecules derived from several cancer cell lines using a proteomic strategy. We identified novel N-glycosylation sites on CEA and further precise investigation revealed that the N-glycosylation patterns were varying among various cancer cell lines. Furthermore, two novel CEA splice variants were identified in gastrointestinal cancer cell lines. Those transcripts were not expressed in normal tissues. CEA protein isoforms derived from the novel splice variants were also expressed in cancer cell lines, and those protein isoforms were secreted to culture medium. We also found that CEACAM4 expression was unique to a medullary thyroid carcinoma cell line.