ABSTRACT
This chapter explores the available knowledge on structure and function of α6β4, and focuses on the possible connections with the transformed state. The integrin α6β4 could be considered a carcinoma-associated antigen, and, given its nature of adhesion receptor, a role in carcinoma cell invasion and metastasis appears likely. The general tendency is that α6β4 is expressed in epithelial and carcinoma cells, whether or not the normal tissue of origin is a6β4 positive. A notable exception is the breast gland, whose normal epithelium is α6β4 positive, while breast cancer cells tend to be α6β4 negative. Another type of cancer potentially revealing as to the role of α6β4 is represented by head and neck squamous carcinomas. In analogy to other integrins, α6β4 is a heterodimer comprised of structurally unrelated subunits, both glycosylated. Another interesting feature of β4 is that two proteolytic fragments are generally found in purified preparation of α6β4, particularly from tissues such as placenta.
