The clone 528, a mouse monoclonal antibody, specifically reacts with an epitope of the ~170 kDa extracellular protein domain of human epidermal growth factor receptor or commonly known as EGFR. Physiologically EGFR is expressed in the skin, gastrointestinal system, kidney, and other normal tissues as well as aberrantly over expresses in epithelial cancer cells of lung, pancreas, colon, breast, and on the head and neck squamous cell. EGFR signaling is activated upon binding one of its ligands including epidermal growth factor (EGF), transforming growth factor ? (TGF ?), Amphiregulin, and heparin binding-EGF (HB-EGF). Upon activation, EGFR becomes an active homodimer from an inactive monomeric form, resulting in several downstream signal transduction cascades including the MAPK, Akt and JNK pathways, leading to DNA synthesis and cell proliferation closely linked with cancer pathogenesis. The 528 antibody has been reported to block EGF binding to its receptor and inhibits A431 tumor formation in nude mice. Therefore, the anti-EGFR monoclonal antibody based anti-cancer immunotherapy has strong clinical potential against various epithelial solid malignant tumors.