Local insulin-like growth factor-I of ventral prostate was upregulated during long-term castration and may function through the autocrine system

The insulin-like growth factor I (IGF-I) is one of the main mitogens and anti-apoptotic factors, which has an important role in cell proliferation, inhibiting cell death in prostate cancer (PCa), and may act as a replacement for androgen after castration. Characterizing the changes in local IGF-I levels in the prostate after castration, is therefore of great importance for doctors to guide and select therapy models after surgical castration in men with PCa. The present study was performed to detect IGF-I of local ventral prostate (VP) at intervals up to 24 weeks after castration by a combination of reverse transcriptase PCR, western-blot, immunohistochemistry and immunofluorescence. We found IGF-I to be decreased sharply after castration and that mRNA and protein levels reached their minimum at 2 days and 5 days, respectively. The level of IGF-I increased gradually and although mRNA levels remained high for longer than 2 weeks, protein levels remained high for longer than 4 weeks. The epithelium cells of VP express IGF-I and its receptor longer than 2 weeks after castration. These findings suggested that although IGF-I of local VP decreases sharply in short-stage castration, its levels increase gradually and remain at high levels at least until 24 weeks. IGF-I synthesized mainly from epithelial cells, which may function through the autocrine system longer than 2 weeks castration. Prostate Cancer and Prostatic Diseases (2011) 14, 136-142; doi:10.1038/pcan.2011.8; published online 15 March 2011