Insulin-like Growth Factor -1 (igf-¢ñ) Dependence Of The Effect And Mechanism Of Non-hormone In The Prostate Cancer

Backgroud: The Insulin-like growth factor I (IGF-I) is one of the main mitogens and anti-apoptotic factors, which plays 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 prostate after castration, is therefore of great importance for doctors to guide and select therapy models after surgical castration in men with PCa.Objective: To detect the IGF-I levels of ventral prostate (VP) at intervals up to 24 weeks after castration in order to better understand changes in its levels after castration. Additionally, we sought to explore the location of IGF-1 and IGF-I receptor (IGF-IR) in order to find out the mode of action of IGF-I.Methods: Adult male Sprague-Dawley rats (n=405, 3 months old). All rats were randomly divided into normal group (15 rats), test group (195 rats) and sham-operated group (195 rats). In test group, castration was achieved by bilateral orchiectomy through a scrotal incision under chloral hydrate (350 mg/kg) anesthesia. The animals were sacrificed at 1, 2, 3, 5, 7, 10 days, 2, 4, 8, 12, 16, 20, 24 weeks (15 animals per time point). The operation procedure of the sham-operated group was the same as that of the test group except bilateral orchiecomy. VP tissues were removed and weighed at indicated time points. Subsequently, the morphological changes were observed with HE staining. IGF-I levels were detected by RT-PCR and western-blot. The location of IGF-I was dected by immunohistochemistry and immunofluorescence.Results: 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 while 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.Conclusions: 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. Objective: To investigate the effects of silencing IGF-I gene on prostate cancer cell line PC3 in the androgen deprived enviorment, and to explore the mechanism of these effects primarly.Methods: The androgen deprived cell culture was made by Charcoal Stripped fetal bovine serum (FBS). The PC3 cells were divided into control group,castration groups,IGF-I RNAi groups and empty plasmid groups randomly. The cells of the control group were cultured in normal culture medium, the model of cell castration was established by exposing to Charcoal Stripped medium, and IGF-I RNAi group was established by transfected with IGF-I RNAi plasmid. Each group was examined at least 5 times. HE staining and inverted microscope were used to observe the cell morphological changes. The viability of cells in each group was measured by MTT colorimetric method and trypan blue staining. The expression of IGF-I was studied by the methods of immunocytochemistry. The contents of IGF-I, IRS-1 mRNA expression of PC3 were detected with reverse transcription polymerase chain reaction (RT-PCR). The content changes of AKT and p-AKT of PC3 cells were measured by Western Blot. Results: Compared with control group, the cell morphology became worse and cell viability decreased after culturing in the androgen deprivated medium. The expression of IGF-I mRNA and its protein were increased after culturing in the androgen deprivated medium. However, the content of IRS-1 was not changed after cultured in the same medium which is the downstream signal molecules of IGF-I. Compared with castration group, the cell morphology and viability of IGF-I RNAi group decreased. And there were no change between castration groups and empty plasmid groups. The contents of p-AKT were increased after cultured in the androgen deprivated medium. Compared with castration groups the contents of p-AKT decreased after transfected IGF-I RNAi plasmid. There were no significant changes of total-AKT among each group.Conclusions: Although PC3 cell is androgen independent prostate cancer cells, culturing it in androgen deprivated medium still caused the cell morphology and cell viability became worse. This change may related to IGF-I, because its levels increased if cultured PC3 cells in androgen deprivated medium. Silcencing IGF-I cause the contents of p-AKT decreased and cell morphology and viability became worse compared with castration group. The reduction of IGF-I may induce p-AKT decreaed, which may be the reason that induced PC3 cell to apoptosis. IGF-I may be one of the important factors which protect prostate cancer cells surviving in the androgen deprivated medium. Silcencing the expression of IGF-I may be a useful target for prostate cancer treatment.