AREG and colorectal cancer: Other potential biomarkers of cetuximab activity in colorectal cancer include EGFR ligands (epiregulin and amphiregulin) and polymorphisms in EGFR, EGF, and Fc fragment of IgG receptor (Khambata-Ford et al, 2007; Zhang et al, 2007; Graziano et al, 2008; Tejpar et al, 2008a).