Implications of insulin-like growth factor-I for prostate cancer therapies

In the last decade, abundant evidence has suggested that the insulin-like growth factor (IGF) family comprises a multi-component network of molecules involved in the regulation of both physiological and pathological growth processes in the prostate. The IGF axis plays an important role in the tumorigenesis and neoplastic growth of prostate cancer. Epidemiological observations indicate that circulating IGF-I levels are positively associated with increased risk of prostate cancer. Activation of IGF-I receptor (IGF-IR) by IGF-I has mitogenic and anti-apoptotic effects on normal and malignant prostate cells. Therapeutic alternatives in men with progressive prostate cancer after androgen ablation are very limited and more effective therapies are needed for such patients. Inactivation of the IGF-I axis represents a potential target to treat androgen-independent prostate cancer. This review addresses epidemiological studies of IGF-I and therapeutic strategies including reduction of IGF-I levels, inhibition of IGF-IR and the signaling mechanisms involved.