EGFR and colorectal carcinoma: When EGF binds to EGFR, homodimerization or heterodimerization of the receptor, in turn, leads to the activation of two main downstream signaling pathways, RAS-RAF-mitogen-activated protein kinase (RAS-RAF-MAP) and phosphatidylinositol 3-kinase–phosphatase and tensin homolog–protein kinase B (PI3K-PTEN-Akt), for regulating gene expression in CRC cells [24].