Cellular and Molecular Mechanisms of Tumor Invasion

The cellular and molecular mechanisms which are the basis of the phenotypic characteristics determining the ability of tumor cells to invasion are reviewed. These mechanisms include the dysregulation of adhesive interactions of tumor cells with each other or with extracellular matrix, production of the proteases, the locomotory reactions of tumor cells and induction of angiogenesis in tumor. In the review the following subjects are considered and discussed: the structures and functions of the transmembrane adhesion molecules and their ligands; the molecular compositions of the adhesion structures (intercellular or focal adhesions); the adhesion molecules as transducers of the intracellular signals; the alterations in expression or hyperphosphorylation (by oncoproteins) of the adhesion molecules and the cytoplasmic proteins of the adhesion structures as the requisite for invasive activity of tumor cells; production of the proteases by tumor cells, and the regulation of the protease activities by the specific stromal inhibitors; the role of the motogens in acquisition of locomotory phenotype by a tumor cell; the contribution of the topographic cell reactions in tumor invasion; mechanisms of neoangiogenesis, providing with the additional ways for dissemination of tumor cells. KEY WORDS: tumor cells, invasion, adhesion molecules, proteases, motogens, cell locomotion, angiogenesis, metastasis.