雄激素受体共调节因子与雄激素非依赖性前列腺癌

雄激素介导的雄激素受体（AR）信号途径对雄性胚胎的发育及雄激素依赖性靶组织的分化发育是必需的。异常的AR活性与前列腺癌由雄激素依赖转变为雄激素非依赖性密切相关。已证实AR共调节因子参与前列腺癌的发生和发展,并在雄激素非依赖性前列腺癌细胞的增殖中扮演着重要角色。它们的表达失衡,可导致AR转录活性的改变,促进晚期前列腺癌的进展。简要综述了AR共调节因子的类型和功能,及其与雄激素非依赖性前列腺癌的关系。     

前列腺癌雄激素受体和PI3K/Akt信号通路相互作用研究进展

前列腺癌的发生、进展依赖于雄激素,因此去势手术成为治疗晚期前列腺癌的标准疗法。但是去势后大多前列腺癌最终将转化为雄激素非依赖性前列腺癌,甚至进展为激素难治性前列腺癌,使得肿瘤的进展不受低水平雄激素的影响。即使如此,大多数激素非依赖性前列腺癌,依然阳性表达雄激素受体。因而雄激素受体在前列腺癌发生发展中起着重要作用。而PI3K/Akt信号通路能够通过维持细胞生存、抑制细胞凋亡、促进细胞代谢及血管生成等促进前列腺癌进展。本综述旨在总结前人研究,阐述雄激素受体和PI3K/Akt信号通路之间相互作用关系。研究表明Akt信号通路能够正性或者负性调控AR蛋白表达、蛋白的稳定性及其转录活性,从而维持细胞的生存、代谢。而AR即可以通过基因转录途径抑制Akt活化又能通过非转录基因途径激活Akt及其下游蛋白。因此,AR和Akt信号通路相互协同促进前列腺癌的发生及其向雄激素非依赖性前列腺癌进展。     

前列腺癌雄激素受体和PI3K/Akt 信号通路相互作用研究进展

前列腺癌的发生、进展依赖于雄激素,因此去势手术成为治疗晚期前列腺癌的标准疗法。但是去势后大多前列腺癌最终将转化为雄激素非依赖性前列腺癌,甚至进展为激素难治性前列腺癌,使得肿瘤的进展不受低水平雄激素的影响。即使如此,大多数激素非依赖性前列腺癌,依然阳性表达雄激素受体。因而雄激素受体在前列腺癌发生发展中起着重要作用。而PI3K/Akt信号通路能够通过维持细胞生存、抑制细胞凋亡、促进细胞代谢及血管生成等促进前列腺癌进展。本综述旨在总结前人研究,阐述雄激素受体和PI3K/Akt信号通路之间相互作用关系。研究表明Akt信号通路能够正性或者负性调控AR蛋白表达、蛋白的稳定性及其转录活性,从而维持细胞的生存、代谢。而AR即可以通过基因转录途径抑制Akt活化又能通过非转录基因途径激活Akt及其下游蛋白。因此,AR和Akt信号通路相互协同促进前列腺癌的发生及其向雄激素非依赖性前列腺癌进展。     

雄激素受体信号转导途径及其在前列腺癌发展中的作用

前列腺癌是西方男性发病率最高的癌症之一,在采用雄激素阻断疗法后,大部分患者的病情可得到控制,但经过一段时间又会转变为雄激素非依赖型前列腺癌。雄激素受体(AR)在前列腺细胞中扮演重要的角色,它可调节大量基因的表达。在前列腺癌由雄激素依赖型向雄激素非依赖型的转变过程中,AR及其信号途径通过多种方式发挥作用,AR基因的扩增、AR的突变,以及与共激活子之间作用的改变都可能使细胞获得雄激素非依赖型的生长能力。此外,AR还受到多肽生长因子和细胞因子等的调节,表现激素非依赖型的转录激活活性。AR在前列腺癌中作用的阐明对前列腺癌的诊断与治疗有着重大的意义。     

雄激素受体及其辅调节因子在肥胖及胰岛素抵抗中作用的研究进展

雄激素受体(androgen receptor,AR)是核受体超家族的成员,主要通过与配体(雄激素)结合的方式发挥其生物学功能。AR在调节男性精子生成和发育,维持男性第二性征等方面起重要作用。此外,AR在前列腺癌、肝癌等疾病的发生发展中起重要作用。更有趣的是,近来研究发现,AR及其介导的靶基因转录在抵抗肥胖,抑制机体产生胰岛素抵抗中也发挥着不可忽视的作用。AR的辅助调节因子参与调控AR介导的基因转录,通过不同的分子机制影响着AR的活性,并且影响机体能量代谢活动。现就AR结构与功能、AR的辅助调节因子的作用机制及其对脂代谢、胰岛素抵抗等影响进行综述。     

阻断MAPK通路促进雄激素受体招募NCoR并抑制前列腺癌细胞生长

雄激素受体(androgen receptor,AR)是配体调节的转录因子,与前列腺癌的生长和内分泌治疗密切相关.醋酸环丙孕酮(cyproterone acetate,CPA)作为雄激素的拮抗剂已用于前列腺癌的治疗.结合了CPA的AR可与核受体协同抑制因子作用.已证实丝裂原激活的蛋白激酶(mitogen-activated protein kinase,MAPK)可介导生长因子和雄激素受体的信号转导通路的交互作用.我们报道,激活的MAPK抑制结合了CPA的AR招募核受体协同抑制因子(nuclear receptor corepressor,NCoR)至雄激素反应元件上.应用MEK的抑制剂U0126阻断MAPK通路可促进结合了CPA的AR和NCoR相互作用并通过对NCoR的招募增加抑制AR的功能从而阻遏AR靶基因的表达.此外,联合使用CPA和U0126处理稳定表达NCoR的LNCaP细胞可显著抑制前列腺癌细胞的生长.本研究表明,联合应用AR的拮抗剂和MAPK抑制剂有助于前列腺癌的治疗.     

AR在膀胱癌发生发展中作用的研究进展

雄激素受体(androgen receptor,AR)是依赖配体活化的转录因子,同时也是类固醇激素受体超家族中的一员,参与靶细胞的增殖和分化。膀胱癌是存在较大性别差异的肿瘤之一。一些数据表明,AR在膀胱癌的进程中发挥重要作用,并部分解释了膀胱癌在不同性别存在差异的原因,但具体机制远不如其在前列腺癌中的机制明确。主要综述几个与AR有重要联系并参与膀胱癌发生发展的分子,阐述AR介导基因转录及AR辅调节因子在膀胱癌中的作用及机制,为膀胱癌的诊断和治疗提供新的思路和靶点。     

雄激素受体与男性代谢综合征

雄激素受体(androgen receptor,AR)属于核受体超家族成员,以配体依赖的方式介导靶基因的转录活性,并招募一系列辅调节因子调控其转录,发挥其生物学功能。近年研究证实,AR可作为一个正向调节因子,通过影响脂代谢、抑制前脂肪细胞的转化、增强机体对胰岛素的敏感性等途径有效预防肥胖和胰岛素抵抗相关疾病的发生。对AR的结构、作用机制及其对男性脂代谢、胰岛素抵抗等影响的研究进展进行综述。     

雄激素非依赖性前列腺癌细胞雄激素受体靶基因的筛选与初步鉴定

采用染色质免疫共沉淀技术在全基因组水平筛选雄激素非依赖性前列腺癌细胞LNCaP-AI的雄激素受体结合位点,行高通量测序及生物信息学分析共得到2 876个peak（pvalue〈1×10–5）,peak平均长度为673 bp;将peak序列定位到Hg19基因组,共有1 865个靶基因,其中fold enrichment≥10的基因有425个。对peak相关基因进行GO分析发现,与细胞、细胞组分、细胞过程、结合、细胞器相关的基因位列前五位;对peak相关基因进行通路分析发现,与黏着斑、代谢通路、癌症中的转录错误调控、嘌呤代谢等信号通路相关的基因占大多数。筛选出7个候选AR靶基因,采用Real-time qPCR技术分析它们在LNCaP-AI细胞和雄激素依赖性前列腺癌细胞LNCaP中对DTH刺激的反应性,发现DHT刺激可改变7个候选AR靶基因在LNCaP-AI细胞中的表达,为进一步研究雄激素依赖性前列腺癌向非依赖性前列腺癌发展的过程中雄激素受体及其调控的下游靶基因功能起着至关重要的作用。     

前列腺癌与表观遗传修饰

前列腺癌是威胁男性健康的主要恶性肿瘤之一,近年来其发病率呈上升趋势。前列腺癌的发生是遗传学因素和表观遗传因素共同作用的结果。本文简要综述了PcG(polycomb group)蛋白质、AR共调节子和微RNA(microRNA)等表观遗传修饰方式与前列腺癌的联系,希望有助于前列腺癌的诊断和治疗。     

Proteasome activity is required for androgen receptor transcriptional activity via regulation of androgen receptor nuclear translocation and interaction with coregulators in prostate cancer cells

Upon binding to androgen, the androgen receptor (AR) can translocate into the nucleus and bind to androgen response element(s) to modulate its target genes. Here we have shown that MG132, a 26 S proteasome inhibitor, suppressed AR transactivation in an androgen-dependent manner in prostate cancer LNCaP and PC-3 cells. In contrast, MG132 showed no suppressive effect on glucocorticoid receptor transactivation. Additionally, transfection of PSMA7, a proteasome subunit, enhanced AR transactivation in a dose-dependent manner. The suppression of AR transactivation by MG132 may then result in the suppression of prostate-specific antigen, a well known marker used to monitor the progress of prostate cancer. Further mechanistic studies indicated that MG132 may suppress AR transactivation via inhibition of AR nuclear translocation and/or inhibition of interactions between AR and its coregulators, such as ARA70 or TIF2. Together, our data suggest that the proteasome system plays important roles in the regulation of AR activity in prostate cancer cells and may provide a unique target site for the development of therapeutic drugs to block androgen/AR-mediated prostate tumor growth.     

Identification and characterization of androgen receptor associated coregulators in prostate cancer cells

The androgen receptor (AR) is a member of the nuclear receptor (NR) superfamily that mediates the effects of androgens on target tissues. Over the last decade, it has become apparent that NRs require accessory factors for optimal activation of target gene expression. Numerous NR coregulators have been identified, with diverse structures and potential mechanisms of coregulation, creating an increasingly complicated picture of NR action. Due to the expanding complexity of the coregulator field, this review will focus on the AR ligand-binding domain (LBD) and N-terminal interacting proteins identified by our lab. The LBD-interacting proteins ARA70, ARA55 and ARA54 were first characterized and ARA70 was found to have a relatively higher specificity for the AR in human prostate cancer DU145 cells. Characterization of the functional relationship between the AR and these coregulators indicated that ARA70 and ARA55 could enhance the androgenic effects of 17beta-estradiol (E2) and hydroxyflutamide (HF), an antiandrogen commonly used in the treatment of prostate cancer. ARA160, an AR N-terminal interacting protein also known as TATA element modulatory factor (TMF), was subsequently shown to cooperate with ARA70 in enhancing AR activity. Another AR N-terminal interacting protein, ARA24, interacted with the poly-Q tract, a region within the N-terminus of the AR linked to Kennedy's disease (X-linked spinal and bulbar muscular atrophy). More recently, our lab has identified ARA267, a SET domain containing protein, and supervillin, an F-actin binding protein, as AR coregulators. Collectively, the data from these studies indicate that these coregulators are necessary for optimal AR transactivation. Interruption of the interaction between AR and these proteins may serve as a new therapeutic target in the treatment of prostate cancer.     

Interaction of IGF signaling and the androgen receptor in prostate cancer progression

The insulin-like growth factor type I receptor (IGF-IR) has been suggested to play an important role in prostate cancer progression and possibly in the progression to androgen-independent (AI) disease. The term AI may not be entirely correct, in that recent data suggest that expression of androgen receptor (AR) and androgen-regulated genes is the primary association with prostate cancer progression after hormone ablation. Therefore, signaling through other growth factors has been thought to play a role in AR-mediated prostate cancer progression to AI disease in the absence of androgen ligand. However, existing data on how IGF-IR signaling interacts with AR activation in prostate cancer are conflicting. In this Prospect article, we review some of the published data on the mechanisms of IGF-IR/AR interaction and present new evidence that IGF-IR signaling may modulate AR compartmentation and thus alter AR activity in prostate cancer cells. Inhibition of IGF-IR signaling can result in cytoplasmic AR retention and a significant change in androgen-regulated gene expression. Translocation of AR from the cytoplasm to the nucleus may be associated with IGF-induced dephosphorylation. Since fully humanized antibodies targeting the IGF-IR are now in clinical trials, the current review is intended to reveal the mechanisms of potential therapeutic effects of these antibodies on AI prostate cancers.     

Transgelin functions as a suppressor via inhibition of ARA54-enhanced androgen receptor transactivation and prostate cancer cell growth

The androgen receptor (AR) requires coregulators for its optimal function. However, whether AR coregulators further need interacting protein(s) for their proper function remains unclear. Here we describe transgelin as the first ARA54-associated negative modulator for AR. Transgelin suppressed ARA54-enhanced AR function in ARA54-positive, but not in ARA54-negative, cells. Transgelin suppressed AR transactivation via interruption of ARA54 homodimerization and AR-ARA54 heterodimerization, resulting in the cytoplasmic retention of AR and ARA54. Stable transfection of transgelin in LNCaP cells suppressed AR-mediated cell growth and prostate-specific antigen expression, whereas this suppressive effect was abolished by the addition of ARA54-small interfering RNA. Results from tissue surveys showing decreased expression of transgelin in prostate cancer specimens further strengthened the suppressor role of transgelin. Our findings reveal the novel mechanisms of how transgelin functions as a suppressor to inhibit prostate cancer cell growth. They also demonstrate that AR coregulators, like ARA54, might have dual in vivo roles functioning as both a direct coactivator and as an indirect mediator in AR function. The finding that a protein can modulate AR function without direct interaction with AR might provide a new therapeutic approach, with fewer side effects, to battle prostate cancer by targeting AR indirectly.     

A dominant-negative mutant of androgen receptor coregulator ARA54 inhibits androgen receptor-mediated prostate cancer growth.

The ligand-bound androgen receptor (AR) regulates target genes via a mechanism involving coregulators such as androgen receptor-associated 54 (ARA54). We investigated whether the interruption of the AR coregulator function could lead to down-regulation of AR activity. Using in vitro mutagenesis and a yeast two-hybrid screening assay, we have isolated a mutant ARA54 (mt-ARA54) carrying a point mutation at amino acid 472 changing a glutamic acid to lysine, which acts as a dominant-negative inhibitor of AR transactivation. In transient transfection assays of prostate cancer cell lines, the mt-ARA54 suppressed endogenous mutated AR-mediated and exogenous wild-type AR-mediated transactivation in LNCaP and PC-3 cells, respectively. In DU145 cells, the mt-ARA54 suppressed exogenous ARA54 but not other coregulators, such as ARA55-enhanced or SRC-1-enhanced AR transactivation. In the LNCaP cells stably transfected with the plasmids encoding the mt-ARA54 under the doxycycline inducible system, the overexpression of the mt-ARA54 inhibited cell growth and endogenous expression of prostate-specific antigen. Mammalian two-hybrid assays further demonstrated that the mt-ARA54 can disrupt the interaction between wild-type ARA54 molecules, suggesting that ARA54 dimerization or oligomerization may play an essential role in the enhancement of AR transactivation. Together, our results demonstrate that a dominant-negative AR coregulator can suppress AR transactivation and cell proliferation in prostate cancer cells. Further studies may provide a new therapeutic approach for blocking AR-mediated prostate cancer growth.     

20(S)-Protopanaxadiol Inhibition of Progression and Growth of Castration-Resistant Prostate Cancer

Castration-resistant progression of prostate cancer after androgen deprivation therapies remains the most critical challenge in the clinical management of prostate cancer. Resurgent androgen receptor (AR) activity is an established driver of castration-resistant progression, and upregulation of the full-length AR (AR-FL) and constitutively-active AR splice variants (AR-Vs) has been implicated to contribute to the resurgent AR activity. We reported previously that ginsenoside 20(S)-protopanaxadiol-aglycone (PPD) can reduce the abundance of both AR-FL and AR-Vs. In the present study, we further showed that the effect of PPD on AR expression and target genes was independent of androgen. PPD treatment resulted in a suppression of ligand-independent AR transactivation. Moreover, PPD delayed castration-resistant regrowth of LNCaP xenograft tumors after androgen deprivation and inhibited the growth of castration-resistant 22Rv1 xenograft tumors with endogenous expression of AR-FL and AR-Vs. This was accompanied by a decline in serum prostate-specific antigen levels as well as a decrease in AR levels and mitoses in the tumors. Notably, the 22Rv1 xenograft tumors were resistant to growth inhibition by the next-generation anti-androgen enzalutamide. The present study represents the first to show the preclinical efficacy of PPD in inhibiting castration-resistant progression and growth of prostate cancer. The findings provide a rationale for further developing PPD or its analogues for prostate cancer therapy.