Figure 1.

Epidermal growth factor receptor pathway in patients with wild-type and mutant BRAF and KRAS. On the right side of the figure, the normal epidermal growth factor receptor (EGFR) pathway is characterized by the binding of growth factor to the EGFR that leads to regular activation of transcription factors and cell-cycle progression; On the left side, mutations in BRAF or KRAS, which are mutually exclusive, cause the activation of the EGFR pathway and therefore an abnormal increase of nuclear signaling and no response to monoclonal antibodies. EGFR: Epidermal growth factor receptor; MEK: Mitogen-activated protein kinase kinase; MAPK: Mitogen-activated protein kinase; MoAb: monoclonal antibodies; WT: Wild type.