Involvement of N-acetyl-lactosamine-containing sugar structures in the liver metastasis of mouse colon carcinoma (colon 26) cells

Biosynthetic Machinery Involved in Aberrant Glycosylation: Promising Targets for Developing of Drugs Against Cancer

Cancer cells depend on altered metabolism and nutrient uptake to generate and keep the malignant phenotype. The hexosamine biosynthetic pathway is a branch of glucose metabolism that produces UDP-GlcNAc and its derivatives, UDP-GalNAc and CMP-Neu5Ac and donor substrates used in the production of glycoproteins and glycolipids. Growing evidence demonstrates that alteration of the pool of activated substrates might lead to different glycosylation and cell signaling. It is already well established that aberrant glycosylation can modulate tumor growth and malignant transformation in different cancer types. Therefore, biosynthetic machinery involved in the assembly of aberrant glycans are becoming prominent targets for anti-tumor drugs. This review describes three classes of glycosylation, O-GlcNAcylation, N-linked, and mucin type O-linked glycosylation, involved in tumor progression, their biosynthesis and highlights the available inhibitors as potential anti-tumor drugs.

Chemoenzymatic synthesis and lectin binding properties of dendritic N-acetyllactosamine

Proof that multivalency amplifies individual carbohydrate-protein interactions is growing. N-Acetylglucosamine (GlcNAc)-based dendrimers with valencies of two (9), four (10), and eight (11) were prepared in fair to excellent yields (65-99%) on the basis of the rational scaffolding of L-lysine on solid phase using established Fmoc and HOBt chemistry. These GlcNAc dendrimers were then further transformed enzymatically (79-90% yields) into dendritic N-acetyllactosamine (LacNAc) derivatives [di-(12), tetra-(13), and octavalent (14)] using UDPglucose, UDP-glucose 4'-epimerase, and GlcNAc beta-1,4-galactosyltransferase. GlcNAc and LacNAc dendrimers were used to inhibit lectin-porcine stomach mucin interactions. Wheat germ agglutinin and Erythrina cristagalli lectin were used for GlcNAc and LacNAc dendrimers, respectively. Di-, tetra-, and octavalent GlcNAc dendrimers exhibited IC50S of 3100, 509, and 88 microM (6200, 2040, and 703 microM, with respect to monomeric GlcNAc content). IC50s for the LacNAc series were 341, 143, and 86 microM (682, 574, and 692 microM, as compared with monomeric LacNAc content). These data represent more than 20-fold increases in inhibitory potential for dendritic GlcNAc as compared to that for monomeric GlcNAc. Studies with E. cristagalli do not reveal significant increased inhibitory potential with multivalency.

Expression of Lewis(x) sugar structure in the liver metastasis of mouse colon carcinoma (colon 26) cells

Immunohistochemical aspects of the process of experimentally induced metastasis were examined by light and electron microscopy employing a series of labeled carbohydrate-specific monoclonal antibodies as probes. Liver metastasis was induced by injecting mouse colon carcinoma cell (colon 26) into the spleen of Balb/c mice. Labeled anti-Lewis(x) (Le(x)) antibody stained the metastasized colon 26 cells strongly compared with the heterogeneous and faint staining in non-metastasized tumor foci in the spleen or in the subcutaneous space. Other antibodies having specificities for Lewis-related antigens other than Le(x), e.g. those against Le(y), Le(a), Le(b), sialyl Le(x) and sialyl Le(a), did not show any differences in binding between metastasized cells and non-metastasized tumor foci. Immunoelectron microscopy revealed the expression of Le(x)-carbohydrate in the plasma membranes as well as in the intercellular spaces of metastasized colon 26 cells in the liver. Based on these results, it is likely that sugar chains containing the Le(x)-carbohydrate structure are involved in the interactions between colon 26 cells and hepatic cells during the process of liver metastasis.