Carbohydrate to carbohydrate interaction in development process and cancer progression.

Two types of carbohydrate to carbohydrate interaction (CCI) have been known to be involved in biological processes. One is the CCI between molecules expressed on interfacing cell membranes of different cells to mediate cell to cell adhesion, and subsequently induce cell signaling, and is termed trans-CCI. It has been indicated that the Le(x) to Le(x) interaction at the morula stage in mouse embryos plays an important role in the compaction process in embryonic development. GM3 to Gg3 or GM3 to LacCer interaction has been suggested to be involved in adhesion of tumor cells to endothelial cells, which is considered a crucial step in tumor metastasis. The other is the CCI between molecules expressed within the same microdomain of the cell surface membrane, and is termed cis-CCI. The interaction between ganglioside GM3, and multi (>3) GlcNAc termini of N-linked glycans of epidermal growth factor receptor (EGFR), has been indicated as the molecular mechanism for the inhibitory effect of GM3 on EGFR activation. Also, the complex with GM3 and GM2 has been shown to inhibit the activation of hepatocyte growth factor (HGF) receptor, cMet, through its association with tetraspanin CD82, and results in the inhibition of cell motility. Since CCI research is still limited, more examples of CCI in biological processes in development, and cancer progression will be revealed in the future.