Epidermal growth factor receptor (ErbB1) expression in prostate cancer progression: correlation with androgen independence

BACKGROUND: The role of the epidermal growth factor receptor (ErbB1) in the progression of prostate cancer is incompletely understood. METHODS: Tissue microarrays from hormone-naive and advanced androgen-independent tumors were used to investigate the role of ErbB1 in prostate cancer progression. RESULTS: ErbB1 expression in tumor tissues was strongly associated with hormone-refractory status (odds ratio = 6.67, 95% CI = (2.6, 17.4), P = 0.0001). However, ErbB1 overexpression was not a statistically significant covariate in a multivariate proportional hazards model for biochemical failure of hormone-na?ve prostate cancer. Moreover, ErbB1 overexpression was not associated with tumor differentiation (P = 0.44), positive margins (P = 0.53), seminal vesicle invasion (P = 0.69), extraprostatic extension (P = 0.10), or preoperative PSA (P = 0.18) in the hormone-na?ve group. CONCLUSIONS: These findings are consistent with a model in which ErbB1 expression increases during the development of the androgen-independent state, and suggest that drugs targeted toward ErbB signaling could be of therapeutic relevance in the management of advanced prostatic carcinoma.     

Molecular modelling of the androgen receptor axis: rational basis for androgen receptor intervention in androgen-independent prostate cancer

Androgen depletion in combination with antiandrogenic agents is initially highly effective for treating prostate cancer, and is the recommended treatment for more advanced or higher-grade tumours. However, many tumours eventually become insensitive to androgens, even though the androgen receptor (AR) continues to be expressed. Computational chemistry combined with structural analysis of nuclear receptors and determination of binding affinities of natural and designed coregulators (coactivators and corepressors) provides the theoretical framework for the rational design of novel therapeutic agents directed at the AR. Adding alternative groups to various sites throughout the receptor can alter the conformation of the molecule and its functional binding with coactivators or corepressors. Possible molecules can be identified thoroughly and systematically using intelligent high-throughput screening and FASTrack chemistry (three-dimensional crystallography). Applying these techniques should eventually result in therapeutic agents for androgen-independent prostate cancer that can block binding of AR coactivators while simultaneously increasing binding of AR corepressors.     

TR2 orphan receptor functions as negative modulator for androgen receptor in prostate cancer cells PC-3

BACKGROUND: Both androgen receptor (AR) and orphan receptor TR2 (TR2) belong to the steroid nuclear receptor superfamily and are expressed in prostate cancer tissue and cell lines. AR has been known to be involved in prostate proliferation and prostate cancer progression. AR binds to androgen response elements and regulates target gene expression via a mechanism involving coregulators. However, the function of TR2 in prostate and prostate cancer and the relationship between TR2 and AR in the prostate cancer is unclear. METHODS: Transient transfection and CAT reporter gene assays were employed to assess AR-mediated transactivation. The expression level of prostate specific antigen (PSA) was measured by Northern blot analysis. The interaction between AR and TR2 was assessed by glutathione-S-transferase (GST) pull-down assay and mammalian two-hybrid system assay. RESULTS: Orphan nuclear receptor TR2 suppressed androgen-mediated transactivation in prostate cancer PC-3 cells, and over-expression of TR2 suppressed PSA expression. The suppression of AR mediated transactivation by TR2 is not due to competition for the limited coregulator availability by these two receptors, but possibly through the interaction between TR2 and AR nuclear receptors. CONCLUSIONS: TR2 may function as a negative modulator to suppress AR function in prostate cancer. Further studies on how to control TR2 function may result in the ability to modulate AR function in prostate cancer.     

Androgenic and antiandrogenic control on epidermal growth factor,epidermal growth factor receptor,and androgen receptor expression in human prostate cancer cell line LNCaP

Both androgen and antiandrogen treatments enhance the proliferation rate of the hormone-dependent prostate cancer cell line LNCaP, expressing a mutated androgen receptor (AR). We studied the modification of the expression of epidermal growth factor (EGF), of its receptor (EGF-R), and of androgen receptor (AR) in the LNCaP cell line, under basal conditions and during androgen (R1881) and antiandrogen hydroxy-flutamide (OH-FLU) treatment. After prolonged R1881 administration, a marked increase of EGF release was observed, completely blocked by the addition of OH-FLU. The Scatchard plot analysis of EGF-R binding revealed two classes of binding sites with high and low affinity. The administration of OH-FLU alone or combined with R1881 did not modify the affinity constants, while the low-affinity component disappeared after androgen administration. Both androgen and antiandrogen administration led to a significant increase of the EGF-R high-affinity component. AR mRNA and protein levels were downregulated by R1881 treatment. Following OH-FLU administration, AR mRNA was slightly downregulated, and there was not a strict parallelism between AR mRNA levels and AR binding capacity. When combined with R1881, OH-FLU partially counteracted the androgen-induced AR downregulation. Our data show that EGF-R binding capacity is the only parameter constantly raised in cell proliferation with respect to quiescent cells, and highlights the nonunivocal action of OH-FLU on androgen-induced effects.     

雄激素受体反义寡核苷酸对前列腺癌细胞生长的抑制作用

目的　探讨雄激素受体 (AR)反义寡核苷酸 (aODN)对前列腺癌细胞AR表达和生长的抑制作用。　方法　合成 1对AR正、反义寡核苷酸 ,与LNCaP细胞共培养 ,观察LNCaP细胞的增殖情况 ,RT PCR和Westernblot方法检测ARmRNA水平和AR蛋白表达水平。　结果　含ARaODN的培养基培养处于静止期和对数生长期的LNCaP细胞增殖较对照组均明显减慢。RT PCR证实aODN组吸光度A值 (0 .5 3± 0 .18)与ODN组 (1.14± 0 .2 1)差异有显著性意义 (P <0 .0 5 ) ,提示ARaODN可导致LNCaP细胞ARmRNA显著下调。Westernblot分析显示aODN组条带的吸光度A值 (2 6 .35± 1.33)与ODN组 (33.5 1± 1.4 8)之间差异有显著性意义 (P <0 .0 5 ) ,提示ARaODN可下调LNCaP细胞AR蛋白含量。　结论　ARaODN可抑制前列腺癌细胞AR表达并抑制前列腺癌细胞增殖。     

CK2抑制剂四溴肉桂酸对前列腺癌细胞增殖及周期的影响

目的探讨一种新的人工合成CK2选择性抑制剂四溴肉桂（TBCA）,对前列腺癌细胞增殖及周期的影响。方珐CK2选择性抑制剂TBCA应用到多种前列腺癌细胞系,Alamarblue法和克隆形成实验检测细胞生长和增殖能力,流式细胞技术检测细胞周期分布,治疗组与对照组间差异是否具有显著意义采用SPSS统计软件进行分析。站杲低剂量（〈25μmol）TBCA干预下未发现细胞聚集和分离,而在高剂量（〉50μmol）则可观察到细胞明显分离,剂量依赖性抑制细胞生长和增殖（P〈0．05）,半抑制浓度值（IC50）为25μmol。TBCA诱导前列腺癌细胞停滞在G2／M期细胞周期。结论TBCA呈剂量依赖性抑制前列腺癌细胞增殖和细胞周期停滞在G2／M期。     

Involvement of arginine methyltransferase CARM1 in androgen receptor function and prostate cancer cell viability

BACKGROUND: Androgen receptor (AR) may play a role in prostate cancer progression. Coactivator-associated arginine methyltransferase (CARM1) catalyzes methylation of histone H3 at Arg-17. METHODS: Immunohistochemistry of CARM1 was performed on primary prostate cancer specimens. CARM1 recruitment and histone methylation was analyzed by chromatin immunoprecipitation. The effect of CARM1 overexpression or CARM1 knockdown was assessed on reporter assays, cell proliferation, apoptosis, and endogenous androgen target gene expression. RESULTS: CARM1 expression was increased in the nucleus of castration-resistant, but not androgen-stimulated prostate cancer. Androgen stimulation led to CARM1 recruitment and methylation of histone H3 at androgen responsive enhancers. Overexpression of CARM1 stimulated and CARM1 knockdown inhibited AR reporter activity. CARM1 knockdown inhibited cell proliferation and induced apoptosis. CARM1 knockdown inhibited androgen-dependent prostate specific antigen (PSA) and hK2 mRNA expression. CONCLUSIONS: CARM1 is essential for AR function and may play a role in prostate cancer progression. CARM1 may represent a novel therapeutic target in prostate cancer.     

The diverse and contrasting effects of using human prostate cancer cell lines to study androgen receptor roles in prostate cancer

The androgen receptor （AR） plays an important role in the development and progression of prostate cancer （PCa）. Androgen deprivation therapy is initially effective in blocking tumor growth, but it eventually leads to the hormonerefractory state. The detailed mechanisms of the conversion from androgen dependence to androgen independence remain unclear. Several PCa cell lines were established to study the role of AR in PCa, but the results were often inconsistent or contrasting in different cell lines, or in the same cell line grown under different conditions. The cellular and molecular alteration of epithelial cells and their microenvironments are complicated, and it is difficult to use a single cell line to address this important issue and also to study the pathophysiological effects of AR. In this paper, we summarize the different effects of AR on multiple cell lines and show the disadvantages of using a single human PCa cell line to study AR effects on PCa. We also discuss the advantages of widely used epithelium-stroma co-culture systems, xenograft mouse models, and genetically engineered PCa mouse models. The combination of in vitro cell line studies and in vivo mouse models might lead to more credible results and better strategies for the study of AR roles in PCa.     

An androgen-independent androgen receptor function protects from inositol hexakisphosphate toxicity in the PC3/PC3(AR) prostate cancer cell lines

BACKGROUND: Inositol hexakisphosphate (IP6) is a phytochemical exhibiting anticancer activity. Because few prostate cancer (PCa) cell lines have been used to study IP6, we assessed its efficacy in a panel of PCa cell lines. METHODS AND RESULTS: Using WST-1 assays we observed that, although androgens did not modulate its efficacy, IP6 was more active in androgen receptor (AR) negative cells than in AR-positive cells. Stable expression of the AR in PC3 cells (PC3(AR)) decreased the response to IP6, which was reversed by an AR-targeting siRNA. Furthermore, AR expression in PC3 cells resulted in significantly reduced caspase-3 activation (P < 0.001) and DNA fragmentation (P < 0.05) in response to IP6. Similarly, although treatment with IP6 caused the upregulation of NF-kappaB-responsive (IkappaB-alpha, IRF-2) and p53/E2F-responsive genes (Puma, Noxa) in PC3 cells, this increase was reduced in PC3AR cells (P < 0.01). CONCLUSION: We conclude that resistance to IP6 can be linked to a ligand-independent AR function.