FIG A1.

The HGF/MET signaling pathway. Gene amplification, or increased gene dosage, leads to increased messenger RNA expression, which leads to exponential increase in the amount of MET protein receptor (green) expression at the membrane. This in turn yields constitutive activation of the MET receptors through autodimerization, independent of ligand presence or absence, and consequent downstream signaling cascade resulting in oncogenic phenotype. HGF/SF, hepatocyte growth factor/scatter factor (the only known ligand for the MET receptor).