肿瘤干细胞（CSCs）是肿瘤复发和转移的根源，Wnt/β-catenin信号是CSCs维持“干性”的重要机制。研究证实AT2R的活化可抑制肿瘤的生长并诱导凋亡，但其对CSCs的作用尚未见报道。我们前期研究发现，新型AT2R激动剂C21能显著下调前列腺癌干细胞（PCSCs）β-catenin水平、抑PCSCs“干性”并诱导凋亡。本项目拟①通过扩大前列腺癌细胞株研究对象，明确C21对PCSCs作用的普遍性；②围绕AT2R/GSK-3β/β-catenin轴，研究C21调节GSK-3β活性并进一步影响β-catenin及其靶基因，阐明C21抑制PCSCs“干性”并诱导凋亡的分子机制；③在PCSC裸鼠模型中进一步验证C21对PCSCs的抑制作用。本项目的完成将深入阐明C21激活AT2R诱导前列腺癌干细胞凋亡的分子机制，为开发C21成为新型肿瘤治疗药物奠定基础。

Cancer stem cells (CSCs) are subpopulation cells that have an unlimited proliferative potential. CSCs are resistant to conventional therapies, which cause tumor recurrence and remote metastasis. Thus, CSCs-targeting approach appears as a major goal toward the improvement of the clinical outcome of patients with incurable tumors. Compound 21 (C21) is the first selective nonpeptide AT2 receptor(AT2R) agonist, which derived from the prototype nonselective AT1/AT2 receptor agonist L-162,313. C21 exerts a similar biological response as the endogenous peptide angiotensin II (Ang II) after selective activation of the AT2R. Our preliminary data showed that C21 reduce stemness and induce cell apoptosis in prostate cancer stem cells (PCSCs) in a dose-dependent manner, and the cytotoxic effects of C21 were reversed by PD123319, a selective AT2R antagonist. Nevertheless, the molecular mechanism underlying the C21-meidiated cell apoptosis.remains unknown. Accumulating evidences indicate that AT2R regulates the phosphorylation level of GSK-3β, which then affects the expression and activation of β-catenin, thereby regulating the transcription of its downstream target genes including c-myc, cyclin and survivin, but no relevant reports have been reported in tumor cells. Since Wnt/β-catenin signaling is an important regulatory pathway in CSCs, we hypothesis that C21 selectively combine with AT2R in PCSCs, which is then activate GSK-3β by down regulate p-ser9-GSK-3β or up regulate p-tyr216-GSK-3β. The active GSK-3β result in β-catenin degradation and transcription inhibition of various downstream target genes including c-myc, cyclin and survivin, which leads to pro-apoptosis effects..In this project, we plan to test our hypothesis by pursuing the following three specific aims: (1)to confirm the effects of C21 on the prostate cancer stem cells; (2)to investigate the effects of AT2R/GSK-3β/β-catenin on PCSCs stemness and apoptosis; (3)to study the anticancer and prognostic effects of C21 in PCSCs mouse model. This study should ultimately provide a better theoretical basis for further.investigation on C21 as a novel therapeutic drug of AT2R-positive cancer.