ERBB2 and breast cancer: The overexpression of ErbB proteins in different cancer types: lung (overexpression of EGFR in 60% of non-small-cell lung cancer, NSCLC), breast (overexpression of ErbB2 in 20–30% of breast cancer), gastric (overexpression of ErbB2 in 22% of gastric cancer), or colorectal cancer (overexpression of EGFR in 25 to 82% of colorectal cancer) made them an attractive therapeutic target [27, 53–56].