Affibody molecules binding specifically to several cancer relevant cell surface receptors have been generated, including epidermal growth factor receptor (EGFR) [18], HER2 [19], human epidermal growth factor receptor 3 (HER3) [20], insulin-like growth factor 1 receptor (IGF1R) [21], and carbonic anhydrase IX (CAIX) [22]. This evidence concerns the gene ERBB3 and cancer.