Zeb1 Promotes Androgen Independence Of Prostate Cancer Via Induction Of Stem Cell-like Properties

Objective: Although initially effective at regressing tumor growth, androgen deprivation therapies will ultimately fail, rendering a lethal drug-resistant stage commonly known as androgen-independent prostate cancer(AIPC). Development of androgen independence is still a serious clinical problem in current prostate cancer therapy. Whether these residual androgen-independent tumor cells have different morphology and biological traits with those androgen-dependent tumor cells is largely unknown. Many studies implicate that Epithelial-Mesenchymal transition(EMT) plays a critical role during cancer development, progression, metastasis and drug resistance. The aim of this study is to explore and analysis whether and how EMT transcription factor Zeb1 involve the development of AIPC during the transition from androgen dependence to androgen independence.Methods: We analyze the expression of Zeb1 in cells, tissues in mRNA and protein level, using Real-time quantitative polymerase chain reaction(qRT-PCR), immunohistochemistry(IHC), immunofluorescent staining and Western blotting. Through lentivirus based knockdown and overexpression, we detect the alteration of cell morphology and function in vitro and in vivo. Different Zeb1 expression in prostate tissues is analyzed using the student’s T test and chi-square test. Two-sided probability value less than 0.05 is considered to be statistically significant. All statistical analysis is done using Prism Graph Pad5.Results: Compared with androgen-dependent prostate cancer cells(LNCaP, PC3 AR(+) and 22RV1), androgen-independent cell lines(C4-2B, PC3 and DU145) show a higher level of Zeb1, accompanied by increased vimentin and decreased E-cadherin expression. Zeb1 expression is also elevated in prostate tumors generated in the castrated PTEN conditional knockout mice, where co-localization of E-cadherin(an epithelial marker) and Vimentin(a mesenchymal marker) is observed. In addition, compared with benign prostate hyperplasia tissues, Zeb1 is elevated in human prostate cancer samples and is positively associated with metastasis. Furthermore, forced Zeb1 expression in LNCaP cells lead to more resistant to bicalutamide(an anti-androgen drug) with increased capacity of cell migration in vitro and could induce advanced tumor growth after castration in vivo, whereas Zeb1 knockdown induce more sensitive to bicalutamide and inhibit cell migration ability. More interestingly, Zeb1 expression is closely associated with some pluripotency stem cell markers such as Sox2, accompanied by enhanced colonogenesis and sphere-forming capacity, common properties of CSCs. Meanwhile, both Zeb1 and Sox2 are increased in castrated mouse prostate tissues. Further immunoprecipitation assay displays that Zeb1 could bind to Sox2 specifically.Conclusion: EMT transcription factor Zeb1 might promotes androgen independence and metastasis of prostate cancer via induction of stem cell-like properties, indicating that reversing the EMT by targeting Zeb1 might be a potential therapeutic approach to the future treatment of prostate cancer.