Figure 1: Schema of the EGFR activation pathway. EGFR is the transmembrane protein (green) with intrinsic tyrosine kinase (phosphorylation in yellow) activity that regulates cell growth. Its ligands are EGF, tumor necrosis factor alfa (TNFα) and others (red). Ligand binds to the receptor and initiates the activity of signaling pathways through dimerization of the receptor and autophosphorization of the tyrosine residues in the cytoplasm, which activates other downstream pathways including Janus Kinase (JAK) Signal Transducers and Activators of Transcription (STAT) directly and through phosphatidylinositol 4,5 bisphosphate (PIP2), c-Jun N-Terminal Kinase (JNK) and raf-1. Activation of these pathways leads to activation of STAT, c-Fos, c-Jun, and c-myc transcription factors respectively. These transcription factors regulate gene expression leading to cell cycle progression, proliferation, invasion, angiogenesis and metastasis.