欧美……一区二区三区,欧美日韩亚洲另类视频,亚洲国产欧美日韩中字,日本一区二区三区dvd视频在线

Carcinoembryonic antigen （CEA） describes a set of highly related glycoproteins involved in cell adhesion. CEA is normally produced in gastrointestinal tissue during fetal development, but the production stops before birth. CEA are glycosyl phosphatidyl inositol （GPI） cell-surface-anchored glycoproteins whose specialized sialofucosylated glycoforms serve as functional colon carcinoma L-selectin and E-selectin ligands, which may be critical to the metastatic dissemination of colon carcinoma cells. Immunologically they are characterized as members of the CD66 cluster of differentiation. The proteins include CD66a, CD66b, CD66c, CD66d, CD66e, CD66f.Consequently, CEA is usually present at very low levels in the blood of healthy adults （about 2–4 ng/mL）. However, the serum levels are raised in some types of cancer. CEA is an important tumor marker for colorectal and some other carcinomas. The CEA subgroup members are cell membrane associated and show a complex expression pattern in normal and cancerous tissues with notably CEA showing a selective epithelial expression.