Table 5 Biological characteristics of CA19-9, CA125 and CEA

Structure

Tetrasaccharide

Mucin (MUC16)

Glycoproteins

Biosynthesis

Series of glycosyltransferation

Most common application

Pancreatic cancer

Ovarian cancer

Colorectal cancer

Cellular location

Various protein carried

Membrane tethered

Cell surface oriented

Characteristic action modes

1) Glycosylating proteins

2) Binding to E-selectin

3) Promoting angiogenesis

1) Reacting with apical surface of epithelial cells

2) Binding to L-selectin and E-selectin

2) C-terminal domain phosphorylating for cell signalling

1) Homotypic adhering

2) Blocking terminal myogenic differentiation

Reasons for false negative

Biosynthesis failure owing to absence of crucial glycosyltransferase

Reasons for false positive

1) Bile duct obstruction

2) Liver damage

2) Pancreatitis

1) Menstruation

2) Pelvic inflammatory disease

2) Endometriosis

1) Inflammatory bowel diseases

2) Smoking

2) Colon polyps