Advances in targeting human epidermal growth factor receptor-2 signaling for cancer therapy

Human epidermal growth factor receptor (HER)-2 is a member of the HER tyrosine kinase family, which regulates cell growth and proliferation. HER-2 is overexpressed in 20% to 30% of breast cancers and has been associated with an aggressive phenotype and a poorer prognosis, making it an appealing therapeutic target. Since 1998, the anti-HER-2 antibody trastuzumab has been used for the treatment of women with HER-2-positive metastatic breast cancer. Results from large trials have established a role for trastuzumab in the adjuvant setting for the treatment of high-risk primary breast cancer as well. Tyrosine kinase inhibitors that target HER-2 are also very promising therapies and are likely to be incorporated into clinical practice in the near future. HER-2-targeted therapies represent a major step forward in achieving our goal of delivering individualized targeted therapy for breast cancer. However, there are many unanswered questions about the optimal use of these agents. Ongoing research will better elucidate the best combination therapies to overcome resistance to HER-2-targeted agents and will help identify patients at high enough risk to warrant their toxicity.