EGFR (Epidermal growth factor receptor, ErbB-1) is a receptor tyrosine kinase (RTK) that is one of four members of the EGFR/ErbB family of receptor tyrosine kinases. EGFR plays a key role in the regulation of essential normal cellular processes and in the pathophysiology of hyperproliferative diseases such as cancer. Activation of the EGFR signaling pathway has been linked with increased cell proliferation, angiogenesis, metastasis and decreased apoptosis. Phosphorylation of EGF receptor (EGFR) at Tyr845 in the kinase domain is implicated in stabilizing the activation loop, maintaining the active state enzyme, and providing a binding surface for substrate proteins. c-Src is involved in phosphorylation of EGFR at Tyr845. The SH2 domain of PLCgamma binds at phospho-Tyr992, resulting in activation of PLCgamma -mediated downstream signaling.