激素难治性前列腺癌组织中雄激素受体蛋白表达的研究

背景与目的:近来有研究报道,在激素难治性前列腺癌(hormonerefractoryprostatecarcinoma,HRPC)中发现有雄激素受体(androgenreceptor,AR)基因扩增,并提出AR基因扩增可能是导致激素治疗失败的一个新的分子机制。本研究拟对前列腺癌在激素治疗前和治疗失败后的AR蛋白表达作定量测定,进一步探讨AR表达与HRPC发生的关系。方法:采用放射配体结合分析方法测定28例晚期前列腺癌患者在激素治疗前以及治疗失败后原发癌组织中的AR蛋白含量。结果:28例前列腺癌在治疗前、后癌组织中的AR蛋白平均水平分别为(390.0±204.1)和(690.4±444.0)fmol/mgProtein,两者间差异有显著性(P<0.001)。其中10例在治疗后12个月内复发,其AR蛋白平均水平在治疗前、后分别为(398.2±199.5)和(448.2±274.1)fmol/mgProtein两者间差异无显著性(P>0.20),其余18例的AR蛋白平均水平在治疗前、后分别为(386.4±212.3)和(824.9±468.6)fmol/mgProtein,两者间差异有显著性(P<0.001)。结论:AR蛋白水平升高可能是前列腺癌对激素治疗不敏感的原因之一。     

Collocation of androgen receptor gene mutations in prostate cancer.

Consistent with both the development of the normal prostate gland and prostate tumorigenesis being dependent on testicular androgens, targeting the androgen-signaling axis (i.e., androgen ablation therapy) remains the predominant treatment regime for patients with metastatic prostate cancer. Although there is a very good initial response to androgen ablation, these treatments are essentially palliative. Recent evidence suggests that treatment failure may not result from a loss of androgen signaling but, rather, from the acquisition of genetic changes that lead to aberrant activation of the androgen-signaling axis. A consistent finding is that androgen receptor (AR) gene mutations, present in metastatic prostate cancer and in human prostate cancer cell lines as well as in xenograft and other animal models, result in decreased specificity of ligand-binding and inappropriate receptor activation by estrogens, progestins, adrenal androgens, glucocorticoids and/or AR antagonists. Because a significant proportion of missense mutations in the AR gene reported in prostate cancer collocate to the signature sequence and AF-2, two discrete regions of the ligand-binding domain critical for androgen signaling, we recently proposed that collocation of mutations identified in prostate cancer would identify additional regions of the AR important in receptor function. This approach led to the identification of a four-amino acid region at the boundary of the hinge and ligand-binding domains of the receptor that forms half of a potential protein-protein binding site. AR gene mutations have also been identified that collocate to areas in the DNA-binding domain, to the NH(2)-terminal transactivation domain, and to the hinge region in prostate tumors. In nearly every case, missense mutations in the AR gene identified in prostate cancer that collocate to discrete regions of the receptor contribute to altered androgen signaling and provide a potential mechanism to explain the reemergence of tumor growth during the course of hormone ablation therapies.     

Androgen receptor coregulators and their involvement in the development and progression of prostate cancer

The androgen receptor signaling axis plays an essential role in the development, function and homeostasis of male urogenital structures including the prostate gland although the mechanism by which the AR axis contributes to the initiation, progression and metastatic spread of prostate cancer remains somewhat enigmatic. A number of molecular events have been proposed to act at the level of the AR and associated coregulators to influence the natural history of prostate cancer including deregulated expression, somatic mutation, and post-translational modification. The purpose of this article is to review the evidence for deregulated expression and function of the AR and associated coactivators and corepressors and how such events might contribute to the progression of prostate cancer by controlling the selection and expression of AR targets.     

Targeting persistent androgen receptor signaling in castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC), the invariably lethal phenotype of advanced prostate cancer, represents a clinical state defined by disease progression despite reduction of testosterone to castrate levels (i.e., ≤50 ng/dL). Although resistant to androgen-deprivation therapy (i.e., LHRH agonists/antagonists), CRPC continues to depend on the androgen receptor (AR)-signaling pathway. Supporting the importance of AR-signaling in a castration-resistant state, the next-generation AR-signaling inhibitors enzalutamide and abiraterone have been shown to afford a survival benefit in men with metastatic CRPC. However, primary and secondary resistance mechanisms to these agents inevitably drive continued disease progression—often as a result of re-activation of AR-signaling. With increased understanding of the mechanisms underlying how continued AR-signaling occurs in spite of drugs like abiraterone and enzalutamide, a new wave of therapies is emerging designed to more effectively target AR-signaling. This review will focus on the more clinically relevant mechanisms of CRPC drug resistance and our ongoing efforts to develop drugs to target these mechanisms.     

Hypoxia increases androgen receptor activity in prostate cancer cells

Recent studies show that prostate cancer cells are able to survive in a hypoxic tumor environment, and the extent of tumor hypoxia correlates with poor clinical outcome. Androgen deprivation, the most common form of prostate cancer therapy, was itself shown to induce a state of transient hypoxia at the microenvironmental level. Because androgen receptor (AR) signaling plays a critical role in prostate cancer, we investigated the effect of hypoxia in regulating AR function. We found that in LNCaP prostate cancer cells, AR binding to the androgen-responsive element (ARE), prostate-specific antigen accumulation, and ARE-reporter gene activity were increased after hypoxia treatment. Hypoxia-enhanced AR function was also observed when AR was exogenously introduced into AR-null DU145 cells. Confocal microscopy and chromatin immunoprecipitation assays showed that AR translocation to the nucleus and AR recruitment to the prostate-specific antigen promoter were facilitated after hypoxia treatment. The AR stimulatory effect seemed to be ligand-dependent because it was abrogated when cells were cultured in an androgen-depleted medium, but was restored with the addition of R1881, a synthetic androgen. The sensitivity of AR activation to R1881 was also increased after hypoxia treatment. Although concentrations of <1 nmol/L R1881 did not induce ARE reporter activity under normoxic conditions, exposure to hypoxia greatly potentiated the AR response to low levels of R1881. Collectively, our results provide compelling evidence that changes in hypoxia/reoxygenation stimulate AR trans-activation and sensitization. The AR-stimulatory effect of an unstable tissue oxygenation milieu of a tumor is likely to contribute to treatment resistance and the emergence of recurrent prostate cancer.     

Interleukin-6 induces androgen responsiveness in prostate cancer cells through up-regulation of androgen receptor expression.

Interleukin-6 (IL-6) induces prostate cancer (CaP) cell proliferation in vitro. Several lines of evidence suggest that IL-6 may promote CaP progression through induction of an androgen response. In this work, we explored whether IL-6 induces androgen responsiveness through modulation of androgen receptor (AR) expression. We found that in the absence of androgen, IL-6 increased prostate-specific antigen (PSA) mRNA levels and activated several androgen-responsive promoters, but not the non-androgen responsive promoters in LNCaP cells. Bicalutamide, an antiandrogen, abolished the IL-6 effect and IL-6 could not activate the PSA and murine mammary tumor virus reporters in AR-negative DU-145 and PC3 cells. These data indicate the IL-6 induces an androgen response in CaP cells through the AR. Pretreatment of LNCaP cells with SB202190, PD98059, or tyrphostin AG879 [p38 mitogen-activated protein kinase (MAPK), MAP/extracellular signal-regulated protein kinase kinase 1/2, and ErbB2 MAPK inhibitors, respectively) but not wortmannin (PI3-kinase inhibitor) blocked IL-6-mediated induction of the PSA promoter, which demonstrates that IL-6 activity is dependent on a MAPK pathway. Finally, IL-6 activated the AR gene promoter, resulting in increased AR mRNA and protein levels in LNCaP cells. These results demonstrate that IL-6 induces AR expression and are the first report of cytokine-mediated induction of the AR promoter. Taken together, our results suggest that IL-6 induces AR activity through both increasing AR gene expression and activating the AR in the absence of androgen in CaP cells. These results provide a mechanism through which IL-6 may contribute to the development of androgen-independent CaP.     

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.     

Upregulation of the androgen receptor during prostate cancer progression

The androgen receptor is one of the central factors in mediating prostate cancer progression and is an important target for treatment. Several possible mechanisms have been put forth as to how it promotes this process. In the January 2004 issue of Nature Medicine, Chen et al. report that the androgen receptor is consistently upregulated as hormone sensitive prostate cancer changes to a hormone refractory state. They also show that this change is intricately involved during the development of resistance to androgen ablation therapy.     

Novel drugs targeting the androgen receptor pathway in prostate cancer

After decades of limited success in the treatment of castration-resistant prostate cancer (CRPC), five novel therapeutics were granted Food and Drug Administration regulatory approval in the last 4 years based on several randomized phase III studies that have reported a survival benefit. Among them, two drugs targeting the androgen receptor pathway, namely abiraterone acetate and enzalutamide, have demonstrated that targeting androgen signalling following progression to classical androgen blockade continues to be an effective strategy despite the emergence of resistance mechanisms to sequential treatments. In addition to these two approved drugs, several other promising agents that block steroidogenesis interact with the androgen receptor or modulate post-receptor signal transduction that are undergoing clinical evaluation. This issue reviews the current data and the state of development of novel androgen receptor-targeting drugs and further discusses how this revolution in therapeutic armamentarium for the treatment of CRPC has raised challenges for clinicians about the optimal usage of these compounds.     

雄激素非依赖性前列腺原位癌动物模型建立及Pim-1表达研究

目的建立雄激素非依赖性前列腺原位癌动物模型,研究Pim-1基因及蛋白在该动物模型的表达。方法采用原位种植包埋法和外科手术去势技术,分别建立雄激素依赖、去势3d和雄激素非依赖性前列腺原位癌动物模型。分别采用基因芯片技术、酶联免疫法和免疫组织化学等实验方法,研究3组肿瘤组织中pim-1基因和蛋白表达的变化。结果 Affymetrix表达谱芯片技术检测结果显示,雄激素非依赖组Pim-1表达高于雄激素依赖组,差异有统计学意义,差异倍数为2.307 71;去势3d组与雄激素依赖组之间差异无统计学意义,差异倍数为1.108 67。ELISA检测结果显示,去势3d组血清睾酮浓度为（2.27±0.035）ng/mL,与雄激素依赖组的（9.02±0.99）ng/mL比较,差异有统计学意义,t=19.28,P〈0.01;雄激素非依赖组为（0.29±0.068）ng/mL,与雄激素依赖组比较,差异有统计学意义,t=24.87,P〈0.01;空白对照组为（9.23±0.78）ng/mL,与雄激素依赖组比较,差异无统计学意义,t=0.45,P=0.998。去势3d组PSA浓度为（0.17±0.032）ng/mL,与雄激素依赖组的（0.48±0.025）ng/mL比较,差异有统计学意义,t=21.82,P〈0.05;雄激素非依赖组为（0.87±0.023）ng/mL,与雄激素依赖组比较,差异有统计学意义,t=31.53,P〈0.05;空白对照组为0ng/mL,与雄激素依赖组比较,差异有统计学意义,t=41.80,P〈0.01。免疫组织化学结果显示,雄激素非依赖组Pim-1蛋白表达量为0.024±0.001 9,明显高于雄激素依赖组的0.017±0.002 1,差异有统计学意义,t=8.27,P〈0.05;去势3d组为0.018±0.001 3,与雄激素依赖组比较,差异无统计学意义,t=1.17,P=0.252。结论成功建立雄激素非依赖性前列腺原位癌动物模型,Pim-1与雄激素非依赖性前列腺癌有高度相关性。     

Genetic alterations of androgen receptor gene in Japanese human prostate cancer

In order to determine the significance of androgen receptor (AR) gene mutations for Japanese prostate cancers, we examined the entire coding region, from exon A to H, in 36 primary lesions. Five in stage A, 12 in stage B, six in stage C and 13 in stage D were subjected to PCR-SSCP analysis for genomic DNA and nucleotide sequencing. Mutations were detected in five samples (14%). Two in stage D and refractory to anti-androgen treatment showed mis-sense mutations. The other three showed changes in the length of the CAG repeat in exon A, with an expansion or a contraction of one repeat unit. However, no association with changes in AR function was indicated because they had not been refractory to hormone therapy. Since these latter three tumors were associated with microsatellite instability, the changes might have been the result of an impairment of mismatch repair. This study indicates that AR gene mutations play a role, in only a subset of prostate cancer patients, in a treatment-refractory state.