|2||The epidermal growth factor receptor (EGFR) is a cell surface receptor belonging to the ErbB family tyrosine kinase receptors. EGFR is involved in cell growth control through its role in the two main intracellular pathways, the mitogen-activated protein kinase (MAPK) pathway and the phosphatidylinositol 3-kinase- (PI3K-) protein kinase B (AKT) pathway. The over-expression or mutation of EGFR may be responsible for the constitutive activation of these pathways. In the colorectal cancer, the EGFR has been found to be frequently over expressed, and may be associated with tumor stage and prognosis. In a subset of such patients, the addition of anti-EGFR monoclonal antibodies to the conventional chemotherapeutic regimens may expand response rates and increase progression-free survival. Somatic EGFR mutations are infrequent in colorectal cancers. The frequency varies from 0.34 to 3.3% in Western population, and from 12% to 22.4% in Asians. R776H is a recurrent mutation in the hinge region of the kinase domain and is known to activate EGFR in a ligand independent manner. In some cases, the possibility of R776H variant being of germline origin, cannot be excluded. The clinicopathologic correlation of EGFR mutations in colorectal cancers continues to be explored.|
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