New Insights into the Role of the Insulin-Like Growth Factors in Breast Cancer

The insulin-like growth factor-1 hormonal axis has emerged in recent years as a promising therapeutic target in oncology. Empirical support to this view was provided by pre-clinical studies showing that insulin-like growth factor-1 receptor expression and activation constitute fundamental prerequisites for breast cancer development. Unfortunately, the vast majority of phase III clinical trials using monoclonal antibodies against the receptor have been disappointing. As a result of these negative outcomes there is an urgent need to identify predictive biomarkers that may identify potential responders. The present review article is aimed at providing an overview of the role of the insulin-like growth factor-1 axis in breast cancer. Circulating insulin-like growth factor-1 constitutes a risk factor for a number of malignancies, including breast cancer, and various members of the insulin-like growth factor-1 system are produced by the tumoral cells or by stromal cells. In addition, we provide evidence that the mechanism of action of insulin-like growth factor-1 involves interactions with the estrogen receptor as well as with the breast cancer gene-1. Finally, lifestyle factors that are related to insulin-like growth factor-1, such as obesity, have been suggested to have an effect on breast cancer.