| Background: Prostate cancer is one of the most common malignant tumors in men,ranking first in the incidence of prostate cancer and second in mortality in the United States.In China,the incidence of prostate cancer is also on the rise,which has become a malignant tumor seriously affecting the health of Chinese men.Therefore,understanding the pathogenesis of prostate cancer is of great significance for the effective diagnosis and treatment of prostate cancer.The etiology of prostate cancer is a complex and multifactorial process,which is closely related to age,family history,race,diet,androgen level and other factors,but the current research is still not fully clear.Epidemiological studies suggest that serum insulin-like growth factor-1(IGF-1)is positively correlated with the occurrence and development of prostate cancer.However,some studies have shown that serum IGF-1 has no value in the prognosis of prostate cancer.Therefore,the relationship between serum IGF-1 and prostate cancer is still uncertain,and is the elevation of serum IGF-1 a cause or a result of prostate cancer? Can serum IGF-1 play a direct role in the occurrence and development of prostate cancer? It is still unclear,so the role of serum IGF-1 in prostate cancer is still a field worthy of study.Objective: In this study,we intend to simulate the effect of high serum level of IGF-1 on the pathological progress of prostate cancer mice by using genetically engineered prostate cancer mice model,to detect the changes of prostate tissue morphology,serology and related molecules in mice,and to verify the relevant mechanisms by the nude mice and prostate cancer cells.Combining with clinical prostate cancer specimens,we will identify the relationship between IGF-1 and prostate cancer.To explore the role of serum IGF-1 in the occurrence and development of prostate cancer and to further study the related mechanisms,so as to provide a new idea for clinical diagnosis and treatment of prostate cancer.Method: 1.Using genetic engineering model mice,the transgenic prostate cancer model Hi-Myc mice were hybridized with liver-specific IGF-1 transgenic mice model-HIT mice,and the double transgenic mice Hi-Myc/HIT mice with both endogenous serum IGF-1 hypersecretion and Myc mutation were obtained.The prostate cancer model of mice with high serum IGF-1 level in vivo was simulated.By histomorphology,pathology and serology,the effects of serum IGF-1 on prostate cancer in Hi-Myc mice were analyzed.2.q PCR,immunohistochemistry,immunofluorescence and Western blot were used to detect the important molecules in the IGF-1 signaling pathway in prostate tissue of mice in each group and to verify the possible signaling pathway of IGF-1 promoting the prostate development of Hi-Myc mice.3.Human prostate tissues were detected by q PCR,immunohistochemistry,Western blot,and the expression of various molecules and relevance analysis in the related signaling pathways such as IGF-1 were analyzed.4.Human prostate cancer cell lines PC3 and DU145 were tested in vitro,and were induced by IGF-1 or blocked by PI3 K inhibitor LY294002.Mitochondrial membrane potential,mitochondrial apoptosis,q PCR,immunofluorescence and Western blot were used to further verify whether the effect and mechanism of IGF-1 on prostate cancer cell lines were consistent with the results in vivo.5.Prostate cancer xenografts in nude mice: single cell suspension prepared by DU145 cells was inoculated subcutaneously on the shoulder of nude mice.After tumorigenesis,IGF-1 was injected or combined with LY294002.The effect of IGF-1 on subcutaneous tumors in nude mice was observed,and the effect of LY294002 in vivo was verified.Result: 1.Serum IGF-1 can promote the occurrence and development of prostate cancer in Hi-Myc mice(1)Anatomical and serological analysis of 6-month-old mice showed that the serum levels of IGF-1 and the size and weight of prostate were increased in double-transgenic Hi-Myc/HIT mice compared with Hi-Myc mice.(2)Serum PSA and PAc P activity are valuable markers for prostate cancer.The serum PSA level and PAc P activity of Hi-Myc/HIT mice were significantly higher than those of Hi-Myc mice,WT mice and HIT mice.(3)According to the pathological diagnostic criteria,the incidence of prostate cancer in 6-month-old Hi-Myc mice was 37%,while that in Hi-Myc/HIT mice was 78%.There were significant differences.While WT mice and HIT mice had no obvious prostate lesion.It suggested that serum IGF-1 increased the incidence of prostate cancer in Hi-Myc mice.(4)Serum IGF-1 increased intraprostatic metastasis of prostate cancer in Hi-Myc mice and decreased the differentiation of prostate cancer.2.Serum IGF-1 reduces apoptosis of prostate cancer cells in Hi-Myc mice through AKT/Fox O3a/Bim signaling pathway(1)Tunel assay showed that the percentage of apoptotic cells in prostate DLP of Hi-Myc/HIT mice was significantly lower than that of Hi-Myc mice.(2)Serum IGF-1 and c-Myc can synergistically promote the expression of IGF-1R in prostate of mice and the activation of downstream signaling pathways.(3)Serum IGF-1 can negatively regulate the expression of Fox O3a/Bim signaling pathway through AKT pathway,which can alleviate the apoptosis of Hi-Myc/HIT mice and promote the progress of prostate cancer.3.Expression of IGF-1 and Fox O3a/Bim signaling pathways in human prostate tissue specimens(1)The expressions of IGF-1 and IGF-1R in prostate cancer tissues were up-regulated compared with benign prostatic hyperplasia tissues,while the expressions of Fox O3 a and Bim were down-regulated in prostate cancer tissues.(2)In prostate cancer tissues,the expression of IGF-1R was negatively correlated with that of Fox O3 a,but positively correlated with that of Fox O3 a and Bim.4.IGF-1 negatively regulates Fox O3a/Bim signaling pathway through PI3K/AKT pathway to reduce mitochondrial apoptosis in prostate cancer PC3 and DU145 cells(1)IGF-1 increases the viability of prostate cancer cells by inhibiting the mitochondrial apoptosis pathway of PC3 and DU145 cells.(2)IGF-1 negatively regulates Fox O3a/Bim expression in PC3 and DU145 cells through PI3 K pathway.(3)The treatment of PC3 cells with IGF-1 resulted in the translocation of Fox O3 a from nucleus to cytoplasm,which could be reversed by PI3 K inhibitors.5.Effects of IGF-1 and LY294002 on prostate cancer xenografts nude mice After subcutaneous tumorigenesis of prostate cancer in nude mice,the average volume and weight of subcutaneous tumors in nude mice treated with IGF-1 for 21 days were significantly larger than those in the control group,suggesting that IGF-1 can promote the growth of subcutaneous tumors in prostate cancer xenografts nude mice.When treated with IGF-1 and LY294002,the volume and size of tumors in nude mice were significantly smaller than those in the group of IGF-1 + saline,suggesting that LY294002 can inhibit the effect of IGF-1 in vivo.Conclusion: In order to investigate the effect of serum IGF-1 on the initiation and development of prostate cancer,a Hi-Myc prostate cancer model with high serum IGF-1 level was established for the first time in vivo.The results showed that serum IGF-1 could promote the initiation and development of prostate cancer in Hi-Myc mice.The molecular mechanism was that serum IGF-1 and c-Myc synergistically promoted the expression of prostate IGF-1R.Sustained activation of the IGF-1R/PI3K/AKT signaling pathway leads to Fox O3 a inactivation through its increased phosphorylation and translocation from the nucleus to the cytoplasm.Thus,the apoptosis of prostate cancer cells was reduced,and the development of prostate cancer in Hi-Myc mice was promoted.Combining with the difference and correlation analysis of the expression of IGF-1R,Fox O3 a and Bim in human prostate cancer and benign prostatic hyperplasia,the results showed that the expression of IGF-1R in human prostate cancer tissue was up-regulated compared with that in benign prostatic hyperplasia tissue,while the expression of Fox O3 a and Bim was down-regulated compared with that in benign prostatic hyperplasia tissue.The expression of IGF-1R in human prostate cancer tissues was negatively correlated with that of Fox O3 a,but positively correlated with that of Fox O3 a and Bim.It is further confirmed that IGF-1 can negatively regulate Fox O3a/Bim signaling pathway to increase mitochondrial membrane potential.Subsequently,the release of cytochrome c into the cytoplasm was blocked and the activation of caspase-9 was suppressed.Thus,the chain of mitochondrial apoptotic pathway is disrupted,the proliferation of PC3 and DU145 cells of human prostate cancer were promoted.LY294002 treatment can reverse the proliferation of PC3 and DU145 cells induced by IGF-1.Using the xenograft model of prostate cancer in nude mice,studies have shown that IGF-1 can promote the growth of xenograft of prostate cancer in nude mice,while LY294002 can inhibit the growth of xenograft induced by IGF-1.This study systematically revealed that serum IGF-1 promotes the progression of prostate cancer by inhibiting cell apoptosis through the Fox O3a/Bim signaling pathway,which provides a new target for clinical diagnosis and treatment of prostate cancer. |
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