ERBB2 and colorectal cancer: Resistance to cetuximab therapy has been extensively studied in colorectal cancers, which shows that amplification of MET or HER2, deletion of PTEN, activation of KRAS, PIK3 CA and other oncogenes could cause persistent activation of growth signaling pathways in cancer cells, thus anti-EGFR mAbs therapy remains ineffective for such tumors [31].