Adhesion molecules in biology and oncology

Abstract

Adhesion molecules are transmembrane glycoproteins acting as a molecular link between the outside and inside of the cell. They have three domains, the extracellular domain, as a signal receptor from outside, the central domain traversing the cell membrane and the intracellular part transporting signals being attached to the cytoskeletal proteins or to linking molecules-enzymes or similar molecules that can induce a chemical change within the cell, or enter into the nucleus and operate as transcription factors. The adhesion molecules are involved in the cell differentiation, migration and sorting. The most direct effect of cell-cell adhesion is on morphogenesis, that is, on the assembly of individual cells into highly ordered tissues and organs. This is characterised by sequential expression of cell adhesion molecules on the surface of embryonic cells. For example, E cadherin is one of the first adhesion molecules that human express, essential for early organisation of the developing embryo. Neoplasia or cancer is viewed as a cell cycle disease. Although this concept implies that every tumor is defective in one or more aspects of the cell cycle control, it clearly does not mean that oncogenesis targets only oncogenes and the cell cycle clock. Development of malignancy appears to require also aberrations in the cell death machinery and cell-cell and/or cell-matrix interactions that cooperate with cell cycle defects. Many of the processes in which adhesion molecules play central role - anchorage dependent growth, apoptosis, differentiation, and migration are those that are characteristically dysregulated in malignancy.