The neu-oncogene: more than a prognostic indicator?

Overexpression of the neu-protein, evidenced as membrane staining by immunohistochemistry, is detected in approximately 20% of invasive duct cell carcinomas, in approximately 50% of in situ duct cell carcinomas, and in almost 100% of cases of Paget's disease. Apart from a growth stimulatory effect, the molecule plays an important role in cell motility of tumor cells by the activity of a motility factor, which acts as a specific ligand for the neu-protein. The motility factor induces chemotaxis of neu-overexpressing breast cancer cells. The motility function of the neu-protein may lead to an increased metastatic potential of neu-overexpressing breast tumors. Also in Paget's disease of the breast, a motility factor secreted by epidermal keratinocytes attracts the neu-overexpressing Paget's cells by chemotaxis and leads to invasion of the epidermis by the tumor cells.