The insulin-like growth factor I receptor: a key to tumor growth?

The insulin-like growth factor I receptor (IGF-IR) belongs to the family of transmembrane tyrosine kinase receptors, like the receptors for platelet-derived growth factor, the epidermal growth factor, insulin, and others. Genetic evidence has shown that the IGF-IR is required for optimal growth in vitro and in vivo. Even more important, however, have been recent findings from several laboratories clearly showing that the IGF-IR is an absolute requirement for the establishment and maintenance of the transformed phenotype, both in vivo and in vitro and in several cell types. These findings indicate that the IGF-IR plays a central role in the mechanism of transformation and, as such, could be a preferred target for therapeutic interventions.