Adhesion proteins in the biology of breast cancer: contribution of CD44.

One of the most important features of tumor cell invasion is the ability to establish or modulate adhesion to other cells or to an extracellular matrix, a process mediated by a large number of adhesion proteins. This review examines how CD44 participates in malignant transformation and progression of the breast epithelium. CD44 is a family of cell adhesion glycoproteins generated by alternative splicing of up to 10 variant exons. Discrete CD44 isoforms are overexpressed in different human cancers, including breast cancer. Recent studies, including our own, have shown that CD44 is involved in two of the three steps of the invasive cascade: adhesion to the extracellular matrix and motility. The overexpression of one of the CD44 variants, CD44v6, is a significant component in the malignant transformation of the breast epithelium and its use as a prognostic marker is presently investigated.