Adhesive properties of metastasizing tumour cells.

Cancer metastasis depends on a functional property which enables tumour cells to depart from the primary site of growth, to disseminate to distant organs and to establish secondary growth. The acquisition of a metastatic phenotype by neoplastic cells most probably involves alterations in their adhesive properties as the migrating cells continuously break and establish cellular contacts throughout the process. In vitro, normal cells of either mesenchymal or epithelial origin usually depend on adhesion to and spreading on a solid substratum (anchoring) for cell division. Neoplastic cells, however, are free of dependence on the support of solid substrata for cell proliferation (anchorage independent). The search for the characteristic alterations in cell adhesion, spreading and morphology which may accompany neoplastic transformation in general and cancer metastasis in particular has engendered a wide range of research activities. These studies have led to the identification of various membrane receptors that mediate cell-cell and cell-extracellular matrix recognition and adhesion on normal and tumour cells. Central to this is the effect of cell adhesion on cell shape and cytoskeleton organization in relation to metastasis. The use of specific antibodies, ligands, drugs and culture conditions permits exploration and identification of some of the macromolecules involved in tumour cell adhesion in vitro and metastasis in vivo. Nevertheless the specificity of the interactions which might determine organ-specific metastasis remains to be elucidated. This paper discusses the interrelation between cell adhesion, cell shape, cytoskeleton and metastasis.