EGF receptor (EGFR) signaling promoting invasion is disrupted in androgen-sensitive prostate cancer cells by an interaction between EGFR and androgen receptor (AR)

We previously demonstrated that expression of androgen receptor (AR) by transfection of the androgen-independent prostate cancer cell line PC3 decreases invasion and adhesion of these cells (PC3-AR) through modulation of alpha6beta4 integrin expression. The treatment with androgens further reduced invasion of the cells without modifying alpha6beta4 expression, suggesting an interference with the invasion process by androgens. Here, we investigated EGF-mediated signal transduction processes that lead to invasion in PC3-AR cells. We show that EGF-induced EGFR autotransphosphorylation is reduced in PC3-AR cells compared to PC3 cells transfected only with the vector (PC3-Neo). EGF-stimulated PI3K activity, a key signaling pathway for invasion of these cells, and EGF-PI3K interaction are also decreased in PC3-AR cells and further reduced by treatment with androgen. Finally, we show that EGFR internalization process was reduced in PC3-AR and LNCaP cells compared to PC3-Neo. Investigations on the location of AR in PC3-AR transfected cells were also conducted. Immunoconfocal microscopy and coimminoprecipitation studies demonstrated the presence of an interaction between EGFR and AR at membrane level in PC3-AR and LNCaP cells. In conclusion, our results suggest that the expression of AR by transfection in PC3 cells confers a less-malignant phenotype by interfering with EGFR signaling leading to invasion through a mechanism involving an interaction between AR and EGFR.     

雄激素受体在去势抵抗性前列腺癌进展中的作用及研究进展

雄激素受体是前列腺癌发生发展的重要因素。雄激素去势疗法是目前治疗前列腺癌的标准疗法,在早期可以有效的抑制肿瘤生长。但2～3年内,肿瘤会复发或进展,形成去势抵抗性前列腺癌。目前关于雄激素去势疗法治疗后去势抵抗性前列腺癌发生发展机制研究的文献较多（其中包括类固醇激素代谢的变化、雄激素受体基因的扩增或过表达、雄激素受体辅助调节因子、雄激素受体剪接变异体、生长因子和／或细胞因子、雄激素受体突变等等机制）,但还没有对具体机制完全了解并形成共识。目前普遍认为在去势抵抗性前列腺癌中,雄激素和雄激素受体在其发生发展中起到了关键的作用。本文就雄激素受体在前列腺癌进展为去势抵抗性前列腺癌的机制中的作用加以综述。     

Adaptive responses of androgen receptor signaling in castration-resistant prostate cancer

Prostate Cancer (PCa) is an important age-related disease being the most common cancer malignancy and the second leading cause of cancer mortality in men in Western countries. Initially, PCa progression is androgen receptor (AR)- and androgen-dependent. Eventually advanced PCa reaches the stage of Castration-Resistant Prostate Cancer (CRPC), but remains dependent on AR, which indicates the importance of AR activity also for CRPC. Here, we discuss various pathways that influence the AR activity in CRPC, which indicates an adaptation of the AR signaling in PCa to overcome the treatment of PCa. The adaptation pathways include interferences of the normal regulation of the AR protein level, the expression of AR variants, the crosstalk of the AR with cytokine tyrosine kinases, the Src-Akt-, the MAPK-signaling pathways and AR corepressors. Furthermore, we summarize the current treatment options with regard to the underlying molecular basis of the common adaptation processes of AR signaling that may arise after the treatment with AR antagonists, androgen deprivation therapy (ADT) as well as for CRPC, and point towards novel therapeutic strategies. The understanding of individualized adaptation processes in PCa will lead to individualized treatment options in the future.     

雄激素非依赖性前列腺癌的研究现状与进展

前列腺癌是泌尿、男生殖系常见的恶性肿瘤之一,在我国发病率虽较低,但近年来呈显著增长的趋势.在我国,前列腺癌被临床上发现时大多已有转移,经雄激素祛除治疗大部分患者病情好转,但最终仍发展为雄激素非依赖性前列腺癌(AIPC).目前临床上将雄激素非依赖性前列腺癌分为三类,其临床表现和预后不一.AIPC的发生、发展机制主要有两方面:①雄激素受体途径;②雄激素受体外的旁路途径,即不依赖于雄激素受体.事实上,大部分AIPC患者两条途径是共同存在、密不可分的.在治疗方面,最近两项大规模的Ⅲ期临床随机对照研究显示,以泰索帝为基础的化疗方案可明显延长AIPC的生存期.其预后与AIPC患者的生存状态、血红蛋白、乳酸脱氢酶等水平有关.     

Reciprocal feedback inhibition of the androgen receptor and PI3K as a novel therapy for castrate-sensitive and -resistant prostate cancer

Gain-of-function of the androgen receptor (AR) and activation of PI3K/AKT/mTOR pathway have been demonstrated to correlate with progression to castration-resistant prostate cancer (CRPC). However, inhibition of AR or PI3K/mTOR alone results in a reciprocal feedback activation. Therefore, we hypothesized that dual inhibition of the AR and PI3K/mTOR pathway might lead to a synergistic inhibition of cell growth and overcome drug resistance in CRPC. Here, we reported that androgen-depletion increased AR protein level and Akt phosphorylation at Ser473 and Thr308 in LNCaP cells. Moreover, we developed resistance cell lines of LNCaP to Enzalutamide (or MDV3100), an AR inhibitor (named as LNCaP ‘MDV-R’) and PF-04691502, a PI3K/mTOR inhibitor (named as LNCaP ‘PF-R’). MTS analysis showed that LNCaP ‘PF-R’ was strongly resistant to Enzalutamide treatment, and on the other hand, LNCaP ‘MDV-R’ was 6-fold resistant to PF-04691502 treatment. Mechanistically, LNCaP ‘MDV-R’ cells had significantly reduced AR, loss of PSA and increase Akt activity in contrast with LNCaP ‘PF-R’ cells. Combined inhibition of PI3K/mTOR and AR pathways with a variety of small molecular inhibitors led to a synergistic suppression of cell proliferation and a profound increase of apoptosis and cell cycle arrest in both androgen-dependent LNCaP and independent CRPC 22Rv1 cell lines. In conclusion, this study provides preclinical proof-of-concept that the combination of a PI3K/mTOR inhibitor with an AR inhibitor results in a synergistic anti-tumor response in non-CRPC and CRPC models.     

Resveratrol modulates the phosphoinositide 3-kinase pathway through an estrogen receptor alpha-dependent mechanism: relevance in cell proliferation

Resveratrol (RES), a natural phytoalexin, has antiproliferative activity in human-derived cancer cells and in rodent models of tumor development. We have previously shown that RES induced apoptotic death in estrogen-responsive MCF-7 human breast cancer cells. Recent data have indicated that the estrogen receptor-alpha (ERalpha), through interaction with p85, regulates phosphoinositide 3-kinase (PI3K) activity, revealing a physiologic, nonnuclear function of the ERalpha potentially relevant in cell proliferation and apoptosis. In our study, using MCF-7, we have analyzed the ability of RES to modulate the ERalpha-dependent PI3K pathway. Immunoprecipitation and kinase activity assays showed that RES increased the ERalpha-associated PI3K activity with a maximum stimulatory effect at concentrations close to 10 microM; concentrations >50 microM decreased PI3K activity. Stimulation of PI3K activity by RES was ERalpha-dependent since it could be blocked by the antiestrogen ICI 182,780. RES did not affect p85 protein expression but induced the proteasome-dependent degradation of the ERalpha. Nevertheless, the amount of PI3K immunoprecipitated by the ERalpha remained unchanged in presence of RES, indicating that ERalpha availability was not limiting PI3K activity. Phosphoprotein kinase B (pPKB/AKT) followed the pattern of PI3K activity, whereas RES did not affect total PKB/AKT expression. PKB/AKT downstream target glycogen synthase kinase 3 (GSK3) also showed a phosphorylation pattern that followed PI3K activity. We propose a mechanism through which RES could inhibit survival and proliferation of estrogen-responsive cells by interfering with an ERalpha-associated PI3K pathway, following a process that could be independent of the nuclear functions of the ERalpha.     

ARFGAP3, an androgen target gene, promotes prostate cancer cell proliferation and migration

ADP ribosylation factor GTPase-activating protein 3 (ARFGAP3) is a GTPase-activating protein that associates with the Golgi apparatus and regulates the vesicular trafficking pathway. In the present study, we examined the contribution of ARFGAP3 to prostate cancer cell biology. We showed that ARFGAP3 expression was induced by 100 nM of dihydrotestosterone (DHT) at both the mRNA and protein levels in androgen-sensitive LNCaP cells. We generated stable transfectants of LNCaP cells with FLAG-tagged ARFGAP3 or a control empty vector and showed that ARFGAP3 overexpression promoted cell proliferation and migration compared with control cells. We found that ARFGAP3 interacted with paxillin, a focal adhesion adaptor protein that is important for cell mobility and migration. Small interfering RNA (siRNA)-mediated knockdown of ARFGAP3 showed that ARFGAP3 siRNA markedly reduced LNCaP cell growth. Androgen receptor (AR)-dependent transactivation activity on prostate-specific antigen (PSA) enhancer was synergistically promoted by exogenous ARFGAP3 and paxillin expression, as shown by luciferase assay in LNCaP cells. Thus, our results suggest that ARFGAP3 is a novel androgen-regulated gene that can promote prostate cancer cell proliferation and migration in collaboration with paxillin.     

雄激素受体在前列腺癌细胞中作用及其靶向治疗的研究进展

雄激素受体(androgen receptor, AR)在前列腺癌的发生发展中扮演重要角色。雄激素剥夺疗法(androgen deprivationtherapy, ADT)早期可成功抑制肿瘤的生长, 但最终导致肿瘤复发并进入激素抵抗阶段。AR对前列腺癌基质细胞起促进肿瘤增殖和转移作用, 是上皮腔样细胞的存活因子, 而对肿瘤干细胞样细胞及上皮基底细胞的增殖起抑制作用, AR在不同类型细胞中的不同作用向当前ADT传统的疗法提出挑战, 为发展新的治疗策略提供理论依据。目前以AR为靶点的靶向治疗药物研发也取得一些进展。本文就AR在前列腺癌不同类型细胞中的作用及靶向治疗方面的进展加以综述。      

Functional analysis of LAT3 in prostate cancer: Its downstream target and relationship with androgen receptor

L-type amino acid transporter 3 (LAT3, SLC43A1) is abundantly expressed in prostate cancer (PC) and is thought to play an essential role in PC progression through the cellular uptake of essential amino acids. Here, we analyzed the expression, function, and downstream target of LAT3 in PC. LAT3 was highly expressed in PC cells expressing androgen receptor (AR), and its expression was increased by dihydrotestosterone treatment and decreased by bicalutamide treatment. In chromatin immunoprecipitation sequencing of AR, binding of AR to the SLC43A1 region was increased by dihydrotestosterone stimulation. Knockdown of LAT3 inhibited cell proliferation, migration, and invasion, and the phosphorylation of p70S6K and 4EBP-1. Separase (ESPL1) was identified as a downstream target of LAT3 by RNA sequencing analysis. In addition, immunostaining of prostatectomy specimens was performed. In the multivariate analysis, high expression of LAT3 was an independent prognostic factor for recurrence-free survival (hazard ratio: 3.24; P = .0018). High LAT3 expression was correlated with the pathological T stage and a high International Society of Urological Pathology grade. In summary, our results suggest that LAT3 plays an important role in the progression of PC.     

Pharmacological inhibition of the Notch pathway enhances the efficacy of androgen deprivation therapy for prostate cancer

Although androgen deprivation therapy (ADT) is a standard treatment for metastatic prostate cancer, this disease inevitably recurs and progresses to ADT‐resistant stage after this therapy. Accordingly, understanding the mechanism of resistance to ADT and finding new approach to enhance the efficacy of ADT may provide a major benefit to PCa patients. In our study, we found upregulated expression of Notch receptors is positive associated with ADT‐resistance progression. Using fluorescent Notch signaling reporter system, we observed that endogenous Notch signaling could be activated after treatment of androgen deprivation in LNCaP cells via activation of Notch3. In addition, exogenous activation of the Notch signaling though Dox‐induced overexpression of any Notch intracellular domains (NICD1‐4) could enhance the resistance of PCa cells to ADT under ex vivo 3D culture conditions and upregulate expression of ADT resistance‐associated phospho‐p38 and Bcl‐2 in LNCaP cells. As a result, pharmacological inhibition of the Notch pathway using γ‐secretase inhibitor (GSI), DAPT, downregulated both phospho‐p38 and Bcl‐2 expression and significantly enhanced the efficacy of ADT in androgen sensitive PCa cells with impaired proliferation and 3D colony formation, increased apoptosis and remarkable inhibition of tumor growth in murine subcutaneous xenograft model. These results indicate that activated Notch signaling contributes to ADT resistance, and suggest that inhibition of the Notch pathway may be a promising adjuvant therapy of ADT for PCa.     

Parenteral oestrogen in the treatment of prostate cancer: a systematic review

The objectives of this study were to assess the effectiveness and safety of parenteral oestrogen in the treatment of prostate cancer, and to examine any dose relationship. A systematic review was undertaken. Electronic databases, published paper and internet resources were searched to locate published and unpublished studies with no restriction by language or publication date. Studies included were randomised controlled trials of parenteral oestrogen in patients with prostate cancer; other study designs were also included to examine dose-response. Study selection, appraisal, data extraction and quality assessment were performed by one reviewer and independently checked by another. Twenty trials were included in the review. The trials differed with regard to the included patients, formulation and dose of parenteral oestrogen, comparator used, outcome measures reported and the duration of follow-up. The results provide no evidence to suggest that parenteral oestrogen, in doses sufficient to produce castrate levels of testosterone, is less effective than luteinising hormone-releasing hormone (LHRH) or orchidectomy in controlling prostate cancer, or that it is consistently associated with an increase in cardiovascular mortality. Further well-conducted trials of parenteral oestrogen are required. A pilot randomised controlled trial comparing transdermal oestrogen to LHRH analogues in men with locally advanced or metastatic prostate cancer is underway in the United Kingdom.     

Darolutamide is a potent androgen receptor antagonist with strong efficacy in prostate cancer models

Darolutamide is a novel androgen receptor (AR) antagonist with a distinct chemical structure compared to other AR antagonists and currently in clinical Phase 3 trials for prostate cancer. Using cell-based transactivation assays, we demonstrate that darolutamide, its diastereomers and its main metabolite keto-darolutamide are strong, competitive antagonists for AR wild type, and also for several mutants identified in prostate cancer patients for which other AR antagonists show reduced antagonism or even agonism. Darolutamide, its two diastereomers and main metabolite are also strong antagonists in assays measuring AR N/C interaction and homodimerization. Molecular modeling suggests that the flexibility of darolutamide allows accommodation in the W742C/L mutated AR ligand-binding pocket while for enzalutamide the loss of the important hydrophobic interaction with W742 leads to reduced AR interaction. This correlates with an antagonistic pattern profile of coregulator recruitment for darolutamide. In vitro efficacy studies performed with androgen-dependent prostate cancer cell lines show that darolutamide strongly reduces cell viability and potently inhibits spheroid formation. Also, a marked down-regulation of androgen target genes paralleled by decreased AR binding to gene regulatory regions is seen. In vivo studies reveal that oral dosing of darolutamide markedly reduces growth of the LAPC-4 cell line-derived xenograft and of the KuCaP-1 patient-derived xenograft. Altogether, these results substantiate a unique antagonistic profile of darolutamide and support further development as a prostate cancer drug.     

Phosphorylation of the androgen receptor is associated with reduced survival in hormone-refractory prostate cancer patients

Cell line studies demonstrate that the PI3K/Akt pathway is upregulated in hormone-refractory prostate cancer (HRPC) and can result in phosphorylation of the androgen receptor (AR). The current study therefore aims to establish if this has relevance to the development of clinical HRPC. Immunohistochemistry was employed to investigate the expression and phosphorylation status of Akt and AR in matched hormone-sensitive and -refractory prostate cancer tumours from 68 patients. In the hormone-refractory tissue, only phosphorylated AR (pAR) was associated with shorter time to death from relapse (P=0.003). However, when an increase in expression in the transition from hormone-sensitive to -refractory prostate cancer was investigated, an increase in expression of PI3K was associated with decreased time to biochemical relapse (P=0.014), and an increase in expression of pAkt(473) and pAR(210) were associated with decreased disease-specific survival (P=0.0019 and 0.0015, respectively). Protein expression of pAkt(473) and pAR(210) also strongly correlated (P<0.001, c.c.=0.711) in the hormone-refractory prostate tumours. These results provide evidence using clinical specimens, that upregulation of the PI3K/Akt pathway is associated with phosphorylation of the AR during development of HRPC, suggesting that this pathway could be a potential therapeutic target.     

SIRT3 inhibits prostate cancer by destabilizing oncoprotein c-MYC through regulation of the PI3K/Akt pathway

SIRT3 is involved in aging-related diseases including cancer, but its role in prostate cancer and detailed regulatory function are not known. We found that SIRT3 was moderately down-regulated in prostate carcinomas. Overexpression of SIRT3 by lentiviral transfection inhibited prostate cancer growth both in vitro and in vivo, whereas knockdown of SIRT3 increased prostate tumor growth. Mechanistically, the tumor suppression effect of SIRT3 was achieved via its inhibition of the PI3K/Akt pathway. Notably, upregulation of SIRT3 suppressed the phosphorylation of Akt, leading to the ubiquitination and degradation of oncoprotein c-MYC; this could be attenuated by constitutive activation of PI3K/Akt signaling. Collectively, our results unveiled SIRT3''s tumor suppressive function and the underlying mechanism in prostate cancer, which might provide therapeutic implications for the disease.     

The interaction of CYP3A5 polymorphisms along the androgen metabolism pathway in prostate cancer

Prostate cancer is a leading solid tumor among men in the Western world. Androgens play an important role in the carcinogenesis and treatment of prostate cancer. CYP3A5 is a cytochrome P450 superfamily member which also has activity in testosterone metabolism. In this study, we looked for two-gene interactions associated with clinical characteristics of prostate cancer in the Finnish population. We used multifactor-dimensionality reduction for the identification of the two-gene interactions in androgen metabolism pathway genes together with clinical characteristics of prostate cancer among 754 genotyped prostate cancer patients. The CYP3A5*3/*3 and SRD5A2 A49T GG genotype interaction was associated with the clinical tumor stage T2-T4 (T-stage, TNM classification) with odds ratio (OR) 2.14, 95% confidence interval (CI) 1.35-3.40. Patients with CYP3A5*3/*3 and KLK3 I179T CC/TC genotypes had increased OR 2.30, 95% CI 1.16-4.58 for metastatic disease. Further, two-gene interaction CYP3A5*3/*3 and KLK3 -252A > G AA was associated with Gleason scores >or=7 with OR 1.52, 95% CI 1.11-2.09. Prostate cancer patients with CYP3A5*3/*3 and KLK -252A > G GG/AG genotypes had decreased OR of 0.70 with 95% CI 0.50-0.98 for high prostate-specific antigen levels at diagnosis. For prostate cancer patients aged below 65 years, the OR for interaction of CYP3A5*1/*3 or *1/*1 and AKR1C3 Q5H CC genotypes was 1.84 with 95% CI 1.03-3.28. For prostate cancer, the best two-gene interaction included genotypes SRD5A2 V89L GG and AKR1C3 Q5H CC with OR 1.30, 95% CI 1.01-1.66. It remains to be clarified whether these polymorphism associations identified here are also present in other populations.     

前列腺癌患者血清睾酮水平、前列腺雄激素受体表达与精索静脉曲张相关研究

目的：研究血清睾酮水平、前列腺雄激素受体（AR）表达与精索静脉曲张的相关性,为临床前列腺疾病诊治提供一定理论依据。方法选取未经药物治疗的64例前列腺癌患者,其中实验组为32例前列腺癌合并精索静脉曲张患者,对照组为32例前列腺癌不伴精索静脉曲张患者,记录两组患者一般情况,并行血清睾酮水平、前列腺雄激素受体检测及病理组织学检查。结果对照组血清睾酮水平为（5.89±1.32）ng/ml,实验组血清睾酮值为（6.07±1.16）ng/ml,差异无统计学意义（P﹥0.05）。实验组前列腺雄激素受体的阳性表达率为62.5%,低于对照组84.4%,差异有统计学意义（P﹤0.05）。AR的表达均与伴精索静脉曲张前列腺癌分期呈负相关（r=-0.318, P﹤0.05）。结论前列腺雄激素受体表达在前列腺癌精索静脉曲张的发病及病情进展中发挥了重要的作用。     

Prostate cancer stem cells: the role of androgen and estrogen receptors

Prostate cancer is one of the most commonly diagnosed cancers in men, and androgen deprivation therapy still represents the primary treatment for prostate cancer patients. This approach, however, frequently fails and patients develop castration-resistant prostate cancer, which is almost untreatable.Cancer cells are characterized by a hierarchical organization, and stem/progenitor cells are endowed with tumor-initiating activity. Accumulating evidence indicates that prostate cancer stem cells lack the androgen receptor and are, indeed, resistant to androgen deprivation therapy. In contrast, these cells express classical (α and/or β) and novel (GPR30) estrogen receptors, which may represent new putative targets in prostate cancer treatment.In the present review, we discuss the still-debated mechanisms, both genomic and non-genomic, by which androgen and estradiol receptors (classical and novel) mediate the hormonal control of prostate cell stemness, transformation, and the continued growth of prostate cancer. Recent preclinical and clinical findings obtained using new androgen receptor antagonists, anti-estrogens, or compounds such as enhancers of androgen receptor degradation and peptides inhibiting non-genomic androgen functions are also presented. These new drugs will likely lead to significant advances in prostate cancer therapy.