Targeting the Type I insulin-like growth factor system for breast cancer therapy

The insulin-like growth factors (IGFs) acting via the type I IGF receptor (IGF-1R) regulate cancer cell proliferation, survival, metabolism and metastasis. Drugs targeting the IGF-1R are being tested in human clinical trials for cancer therapy and it seems likely that this class of drugs could be approved soon. Recent data suggests that insulin receptor, which is closely related to IGF-1R, should also be targeted to maximally inhibit the system. Furthermore, biomarkers that identify patients whose tumors are driven by IGF-1R and biomarkers that allow monitoring or prediction of response are needed. This article reviews the different drugs against IGF-1R that are being tested and how this receptor pathway can be optimally targeted for cancer therapy with an emphasis on breast cancer therapy.