Growth factor receptors have long been known to drive malignant transformation and cancer progression. The epidermal growth factor receptor (EGFR, ErbB, HER) system is likely the best described membrane receptor tyrosine kinase family in malignant tumors. With implementation of the growth-inhibitory anti-HER-2 antibody trastuzumab (Herceptin) for the treatment of HER-2-positive advanced metastatic breast cancer, a new era has dawned in the therapy of this malignant disease. Unfortunately, trastuzumab-sensitive cancers invariably develop resistance to the antibody after some time. Recent...