Targeting IGF-I, IGFBPs and IGF-I Receptor System in Cancer: The Current and Future in Breast Cancer Therapy

The IGF system plays a major role in growth, development and maintenance of homeostasis in normal cells and also contributes towards proliferation of malignant cells. Any disruption in the IGF system has its implications on growth retardation, atherosclerosis, insulin resistance and cancer. Imbalances in the IGF axis are known to contribute towards the progression of breast cancer. Due to the ubiquitous nature of the components of the IGF system, targeting specific members of the axis has gained attention over the past decades. The most elaborately investigated component as a therapeutic target in the system is the IGF-IR and studies have been pursued to inhibit IGF-IR by the administration of monoclonal antibodies and tyrosine kinase inhibitors. Very recently, a novel cell death receptor that binds specifically to IGFBP-3 was identified. It has also been shown that the IGFBP-3/IGFBP-3 receptor may be impaired in breast and prostate cancer. In this review, we present the mechanisms used to target the IGF system in various diseased states, emphasizing on breast cancer. We further discuss currently available therapeutic approaches and summarize the latest patents published in the field of IGF-I/IGF-IR and IGFBP-3/IGFBP-3R systems.