Adhesion molecule expression in breast cancer: the phoenix in tumour metastasis?

Adhesion molecules have a number of diverse roles, amongst which is the control of tissue architecture and the maintenance of tissue integrity. Most tumours have an abnormal architecture and loss of tissue integrity is thought to be an important step in the development of local invasion. Thus, alterations in adhesion molecules may have a role in both tumour development and tumour invasion. The role of these molecules in the establishment of tumour metastases is much less certain. The tumour cells in a metastatic deposit are in a different environment and are faced with a different set of selection pressures, which may drive tumour evolution in a new direction. Metastatic deposits often resemble the tumour of origin and not infrequently show better differentiation. Together with evidence from experimental maintenance systems which shows that maintenance of intercellular contact may prevent apoptosis, this implies a role for adhesion molecules in tumour metastasis.