HER2 as a target for breast cancer therapy.

Importance of the Field: Differential levels of HER2 expression in normal versus HER2-overexpressing breast carcinomas, together with the demonstration of a key role for HER2 in tumor progression, make HER2 an ideal target for specific therapeutic approaches.
Areas Covered in This Review: This review considers the clinical value of trastuzumab and lapatinib, the two HER2-targeted therapies approved for clinical practice. References were chosen by searching the PubMed and MEDLINE datasets using as search term: 'HER2', in association with 'prognosis', 'response', 'trastuzumab', 'lapatinib' and 'resistance'.
What the Reader Will Gain: This review deals with HER2 as a target for breast carcinoma treatment, focusing on anti-HER2 therapies used in clinical practice, their merits and shortcomings.
Take Home Message: The benefit of anti-HER2 therapies demonstrated in clinical trials indicates that HER2 is, to date, one of the most promising molecules for targeted therapy. Nevertheless, since tumor cells utilizing alternative growth signaling pathways through transmembrane receptors as well as intracellular signaling transduction molecules can bypass HER2 blockade, a future ambitious aim is the successful combination of anti-HER2 strategies with drugs directed to molecules that contribute to anti-HER2 resistance.