Preliminary Study On The Role Of Pituitary Tumor-transforming Gene1during Development Of Androgen Independent Prostate Cancer

Background：Prostate cancer is still a significant public health problem. Most patientseventually develop androgen-independent PCa which is poorly responsive to traditionaltherapies. Although the focus of rigorous study, the molecular mechanisms underlyingthe progression of prostate cancer to hormone-independent disease remain unclear.Increased levels of pituitary tumor transforming gene1(PTTG1) lead to tumortransfomation, proliferation and angiopoiesis, leading to cancer development andprogression. PTTG1has been reported to be overexpressed and associated withprognosis and matastasis in a variety of tumors, and siRNA technology could decreaseexpression of PTTG1to supress tumor proliferation. But the role of PTTG1inandrogen-independent prostate cancer is unclear. In our study, an androgen-independentprostate cancer LNCaP subline LNCaP-AI was established, which be used to observethe change of PTTG1expression in LNCaP during the process of culture in hormonedeprivation medium, and decrease PTTG1expression by siRNA technology inLNCaP-AI to acquire its role during the development of AIPC, and to validate itstherapeutic role in AIPC.Objective: In order to provide a new theory for AIPC developemnt and treatment,we try to valuate the novel function of PTTG1in the development of AIPC and theantitumor efficacy of decreasing PTTG1via siRNA technology.Methods:1. An androgen-independent prostate cancer cell model LNCaP-AI wasestablished through long time culture in the hormone deprivation media. Comparedwith LNCaP, androgen receptor expression, proliferation, invasion and PSA secretionwere detected by Western blot, PCR and Transwell trials.2. The change of PTTG1expression in LNCaP during the process of culture in hormone deprivation medium, and the stimulating role to PTTG1expression weredetected by Western blot, RT-PCR technology.3. After decreased expression of PTTG1in LNCaP-AI cell model by siRNAtechnology, cell proliferation, invasion, apoptosis and theraputic role of LNCaP-AIwere detected by Western blot, RT-PCR, Transwell trails and Flow Cytometry. Thesensitivity of androgen receptor antagonist was also evaluated.Result：1. The androgen-independent prostate cancer cell model LNCaP-AI was wassuccessfully established as confirmed by detection of increased androgen receptor,proliferation, enhenced migration in the environment of free androgen hormone.2. The expression of PTTG1was increasing in LNCaP during the process ofculture and stable expression in LNCaP-AI, which was associated with factorsaccording to metastasis in hormone deprivated meida. Insulin or IGF-1decreased theexpression of PTTG1in LNCaP-AI.3. An effective fragment of siRNA selected to reduce expression of PTTG1inLNCaP-AI, which lead to increase apoptosis, reduced migration and decreasedexpression of some factors associated with metastasis and PI3Kand MAPK signalingpathways. siRNA-PTTG1enhanced the sensitivity to androgen receptor antagonist.Conclusion：PTTG1was invovled in the development of androgen-independent prostate cancer,and may be a predictive biomarker of AIPC cell sensitivity to ADT. Direct targeting ofPTTG1however may be relevant to enhance the response of existing and noveltherapeutics in AIPC.