**4.3 HER-2**

The HER-2 protein is a well established target of immunotherapy in breast cancer. The proto-oncogene HER-2 is found on chromosome 17q and encodes a transmembrane tyrosine kinase growth factor receptor. HER-2 over expression occurs in ovarian, pancreatic, gastric, lung and head/neck cancers [65-68]. Twenty to thirty percent of breast cancers have been found to amplify the HER-2 gene or overexpress the HER-2 protein, which portends a poorer prognosis and higher risk of recurrence in patients with both invasive and in situ disease [69].

HER-2 represents an ideal target for antigen-specific vaccines used to treat breast cancer. Over expression of this protein is immunogenic as it induces a T cell immune response causing HER-2 specific antibodies to be present in the serum of breast cancer patient [70]. The feasibility of HER-2 targeted vaccines has been demonstrated in animal models [71]. In addition, a number of phase I and II trials using HER-2 based vaccines of all types have been performed in patients with high risk breast cancer. The vaccines in all of these studies were well tolerated and caused minimal toxicity [18].
