ERBB4 and cancer: Some of the most well-characterized RTKs implicated in cancer include the “HER family”, i.e., epidermal growth factor receptor (EGFR), ErbB2 (neu, HER2), ErbB3 (HER3) and ErbB4 (HER4), as well as VEGF/VEGFR, which is discussed in the following paragraphs [14,15,16,17,18].