Identification of phosphorylation sites in the IGF-1 Receptor

Although Insulin-like Growth Factor (IGF-1) signaling promotes tumor growth and cancer progression, IGF-1 Receptor-targeted therapies have shown poor clinical efficacy. The mechanistic basis for this is unclear as is our understanding of what distinguishes IGF-1R signaling from the closely related Insulin receptor (IR) signaling. This study illuminates both issues. A site in the IGF-1R C-terminal tail incorporating two tyrosines that are not present in the Insulin receptor (IR) was previously shown to be essential for IGF-1-mediated cancer cell survival, migration and tumorigenic growth. Here, we establish that the Y1250/Y1251 site is autophosphorylated in a cell adhesion-dependent manner.