Figure 2.

HER2 pathway. Ligand binding to the extracellular domain of human epidermal growth factor receptor (HER1/3/4) stabilizes the formation of active HER2 heterodimers. Transphosphorylation of tyrosine residues within the intracellular domains results in kinase domains activation. Phosphorylation creates binding sites for adaptor or effector proteins (SOS and PI3K) that activate mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI3K)-Akt pathways. These pathways result downstream in transcription of genes driving cell proliferation, migration, differentiation, and apoptosis.