Insulin-like growth factor-binding protein 5 （IGFBP-5） is a member of the IGFBP family, which consists of six high-affinity binding proteins （IGFBP-1 to IGFBP-6） that regulate the bioavailability and activity of insulin-like growth factors （IGFs）, namely IGF-I and IGF-II. IGFBP-5 is a multifunctional protein that not only modulates IGF signaling but also exhibits IGF-independent functions. It is widely expressed in various tissues, including bone, breast, prostate, and the cardiovascular system, and plays a critical role in cellular growth, differentiation, apoptosis, and tissue development.
IGFBP-5 is involved in various diseases, including cancer, diabetes, and cardiovascular disorders. In cancer, IGFBP-5 exhibits dual roles, acting as either a tumor suppressor or promoter depending on the cellular context. For example, it is overexpressed in aggressive glioblastoma and osteosarcoma, where it promotes tumor invasion and metastasis. Conversely, in breast cancer, IGFBP-5 can inhibit tumor growth by inducing apoptosis.