The epidermal growth factor receptor (EGFR), including EGFR (Erb-B1), HER2/neu (Erb-B2), HER3 (Erb-B3) and HER4 (Erb-B4), is a family of receptor tyrosine kinases representing ideal therapeutic targets because they play a critical role in cancer proliferation and survival (Woodburn, 1999). Here, ERBB4 is linked to cancer.