Expression of Lewisa, sialyl Lewis3, Lewisx and sialyl Lewisx antigens: DISCUSSION Part 3
Qualitative differences between type 1 and type 2 chain antigens: The reason for the difference between the significance of the presence of type 1 and that of type 2 chain carbohydrate structures, which was revealed in the present study, is not known. In general, most type 1 chain determinants such as sialyl Lea antigen are closely related to Le blood group structures, which are substances (ie, carbohydrate human alloantigens) that are present in normal mature cells. On the other hand, type 2 chain antigens such as sialyl Lex are usually present only in immature cells and frequently appear during the course of malignant transformation. The present study also revealed that type 1 chain antigens (Lea and sialyl Lea) are more frequently expressed than type 2 chain antigens (Lex and sialyl Lex) in normal colonic mucosa. In the crypts of normal colonic mucosa, type 1 chain antigens are diffusely observed in cells located in the upper two-thirds of the crypts, whereas type 2 chain antigens are located in the lower one-third of the crypts, in particular, sialyl Lex shows weak staining in very limited parts of some crypts. It has also been elucidated that circulating type 1 chain antigens are more frequently detected in the sera of patients with nonmalignant disorders than type 2 chain antigens, as determined by assay of the same sera. These fundamental qualitative differences between type 1 and type 2 chain antigens may explain why tumours expressing type 1 or type 2 chain antigens have different metastatic behaviour, and why type 1 and type 2 chain antigens have different prognostic value. Further studies are needed to confirm our theories and increase the level of understanding. Time to visit a trusted pharmacy – to begin your treatment now.
In summary, Lex expression and sialyl Lex expression are associated with poor prognosis in colorectal cancer patients. Currently, in the treatment of colorectal cancer, stratification into patient groups to select individuals for appropriate adjuvant therapy protocols is primarily based on clinicopa-thological criteria. Prospective clinical studies on Lex and/or sialyl Lex antigen expression may be helpful in planning additional adjuvant therapies after surgery. Furthermore, administration of sialyl Lex, for example by using sialyl Lex oligosaccharide in the form of liposomes, has been suggested as a therapy for cancers. Ongoing studies concerning the carbohydrate-protein interaction and its possible role in cell-cell adhesion, and the mechanism of metastasis will open new pathways of therapeutic intervention targeted at these molecules.