Expression of peroxisome proliferator-activated receptor (PPAR) in human prostate cancer

BACKGROUND: Recent studies have demonstrated that peroxisome proliferator activator-receptors (PPAR)-gamma is expressed in some cancer cells such as breast, lung, and gastric cancer, and its ligand induces growth arrest of these cancer cells through apoptosis. However, the expression and localization of PPARs in prostate have not been examined. In this study, PPARs expression was investigated in human prostate cancer (PC), prostatic intraepithelial neoplasia (PIN), benign prostatic hyperplasia (BPH), and normal prostate (NP) tissues. METHODS: Tumor specimens were obtained from 156 patients with PC, 15 with PIN, 20 with BPH, and 12 patients with NP tissues. The expressions were investigated by RT-PCR and immunohistochemical methods. RESULTS: Immunoreactive PPAR-alpha and -beta were significantly apparent in PC tissues. Marked expressions of PPAR-alpha and -beta were also detected in PIN, BPH, and NP groups. However, very weak or no expression of immunoreactive PPAR-gamma was found in BPH and NP cases. In contrast, we found significant expression of immunoreactive PPAR-gamma in cancer cells in PC group and in PIN group. CONCLUSIONS: Our results demonstrated that PPAR-gamma is induced in PC, and suggest that PPAR-gamma ligands may mediate its own potent antiproliferative effect against PC cells through differentiation.     

乳腺癌组织中雌激素受体亚型βmRNA和血管内皮细胞生长因子mRNA的表达及其意义

目的探讨雌激素受体亚型β(ERβ)和血管内皮细胞生长因子(VEGF)在乳腺癌组织中的表达及其表达的关系。方法采用半定量逆转录聚合酶链反应(RTPCR)检测35例乳腺癌、12例癌旁乳腺组织和10例乳腺纤维腺瘤组织中ERβmRNA和VEGFmRNA表达,分析其表达之间的关系。结果ERβmRNA在乳腺癌中的表达水平(0.274±0.124)明显低于癌旁乳腺组织(0.538±0.124)和乳腺纤维腺瘤组织(0.459±0.13)(t=6.37、4.09,P均<0.01)。VEGF121、165mRNA在乳腺癌中的表达水平(0.530±0.142、0.336±0.114)明显高于癌旁乳腺组织(0.184±0.098、0.137±0.059)和乳腺纤维腺瘤组织(0.280±0.078、0.187±0.090)的表达(t=6.87和4.69、5.73和3.89,P均<0.01)。VEGF121、165mRNA在有淋巴结转移的乳腺癌组织中表达水平明显高于无淋巴结转移者(P<0.05)。ERβmRNA表达水平与VEGF121、165mRNA的表达水平呈正相关(r=0.785和0.641,P均<0.01)。结论乳腺癌组织中ERβmRNA表达下调,而VEGFmRNA表达上调。VEGFmRNA的表达水平高者可能有利于淋巴结转移。乳腺肿瘤血管生成可能受ERβ的影响。     

Expression of gonadotropin-releasing hormone (GnRH) and GnRH receptor mRNA in prostate cancer cells and effect of GnRH on the proliferation of prostate cancer cells

The purpose of this study was to determine the production of gonadotropin-releasing hormone (GnRH), the co-occurrence of GnRH receptors in prostate cancer cells, and the effect of GnRH on prostate cancer cell proliferation. Four human prostate cancer cell lines were studied. LNCaP is an androgen sensitive prostate cancer cell line, DU-145 and PC-3 are androgen resistant, and TSU-Pr1 is uncharacterized. The expression of GnRH and GnRH receptor mRNAs were assessed by in situ hybridization and the effect of exogenous GnRH on proliferation of prostate cancer cells was measured by thymidine incorporation assay. GnRH mRNA expression, determined by in situ hybridization, was found in 83.48% of the LNCaP, 89.7% of the TSU-Pr1, 86.2% of the PC-3 and 95.3% of the DU-145. Signals of GnRH receptor mRNA were detected in more than 95% of the cells of all four cell lines. The proliferation of the prostate cancer cells grown in media supplemented with peptide hormone lacking charcoal-stripped serum was significantly (P < 0.05) suppressed. No significant effect of GnRH on the proliferation of all four prostate cancer cells was observed. In summary, prostate cancer cells produced GnRH and its receptors, and exogenous GnRH treatment did not affect the prostate cancer cell proliferation. The existence of GnRH and GnRH receptor mRNA in the same cell suggests that the role of GnRH produced by prostate cancer cells would be autocrine. Received: 21 August 1997 / Accepted 15 April 1998     

Expression of estrogen receptor in diseased human prostate assessed by non-radioactive in situ hybridization and immunohistochemistry

To understand the role of estrogen in the pathogenesis of benign prostatic hyperplasia, expressions of estrogen receptor (ER) mRNA and ER protein by in situ hybridization and by immunohistochemistry, respectively, were investigated in human prostatic tissues. In non-malignant region, ER mRNA and ER protein were found in cytoplasm and nucleus, respectively, of stromal cells, but not in glandular epithelial and basal cells. In benign regions, ER mRNA/ER protein positive cells were found in fibromyoadenomatous and myoadenomatous hyperplasia, but not in adenomatous hyperplasia. A striking feature was periacinar arrangement of ER mRNA/ER protein positive stromal cells in all prostate carcinoma treated with androgen withdrawal. The ER mRNA/ER protein positive cells were immunohistochemically identified as fibroblasts, myoblasts, and smooth muscle cells. These results indicate that stromal cells are the primary target of estrogen in prostate, and that androgen withdrawal upregulates the expression of ER gene. © 1995 Wiley-Liss, Inc.     

Association study of polymorphisms in the human estrogen receptor alpha gene and prostate cancer risk

OBJECTIVES: Prostate cancer is a very common hormone-related malignancy in Western countries. It is initially dependent on androgen stimulation but in vitro growth of prostate cancer cells are also dependent on estrogen. Our goal was to elucidate if some polymorphisms of estrogen receptor alpha gene might be associated with the risk of prostate cancer. METHODS: Using DHPLC techniques, each coding exon of the estrogen receptor alpha gene was screened for new polymorphisms in germline DNA from 96 healthy controls and 96 sporadic prostate cancer cases. Identified polymorphisms were then genotyped and their distribution compared between the two populations. RESULTS: Thirteen polymorphisms were identified. A difference was found in the distribution of one newly identified polymorphism, namely a GGGA repeat located in the first intron of the gene. The common wild type genotype consisted of two alleles with five GGGA repetitions (5/5 genotype). Indeed this 5/5 genotype was found in 294/296 controls (99.3%) and 285/294 patients (96.9%; OR, 4.6; 95% CI, 0.99-21.67). Among the nine patients with a different genotype, one was 4/5, seven were 5/6 and one was 6/6. CONCLUSION: These results suggest that variants of the GGGA polymorphism from the estrogen receptor alpha gene may be associated with an increased risk of developing prostate cancer.     

Steroid sulfatase and estrogen sulfotransferase in human prostate cancer

BACKGROUND: Estrogen sulfotransferase (EST) and steroid sulfatase (STS) are known to be involved in in situ estrogen production in estrogen dependent human cancer such as breast cancer, but unknown in prostate cancer. MATERIALS AND METHODS: We first examined whether these enzymes above were expressed and actually involved in estrogen production and metabolism in prostate cancer cell lines (LNCaP, DU-145, and PC-3). We than examined the expression of EST and STS in human prostate cancer tissues obtained from surgery (n = 52) using immunohistochemistry. RESULTS: mRNAs of both enzymes were detected in all prostate cancer cell lines examined, and the synthesis of estrone (E(1)) and estradiol (E(2)) was also confirmed in these cell lines. In addition, STS immunoreactivity was detected in 44 cases (85%) and EST in 39 cases (75%), respectively. CONCLUSIONS: STS and EST are expressed and may be involved in local production and metabolism of estrogens in human prostate cancers.     

Expression of functional protease-activated receptor 1 in human prostate cancer cell lines

Functional protease-activated receptors (PAR) are expressed by a variety of malignant cells. In the present study, RT-PCR assays demonstrated the expression of the thrombin receptor PAR-1 mRNA in human prostate cancer cell lines DU 145, LnCAP, and SV40-immortalized human prostate epithelial cell line PNT1A. In contrast, the additional thrombin receptors PAR-3 and PAR-4 were not detected. PAR-1 protein localized to the cellular surface was detected by flow cytometry in all three cell lines. To demonstrate the functional importance of the PAR-1, the effects of different concentrations of thrombin on cell proliferation kinetics were assessed. The treatment of growth-arrested cells with varying concentrations of thrombin demonstrated dose- and time-dependent effects. At low concentration (<0.5 U/ml), thrombin induced proliferation of all prostate-derived cell lines. Thrombin at higher concentration (1.0 U/ml) initially stimulated PNT1A and LnCAP cells to proliferate (time of thrombin application 24 h and 48 h) followed by inhibited growth when assessed after 72 h of incubation. In contrast, 1.0 U/ml thrombin caused earlier inhibition of DU 145 proliferation starting at 48 h of incubation. Our results suggest that PAR-1 mediates the proliferation-modulating effects of thrombin on prostate cancer cells.     

Immunolocalization of estrogen receptor alpha and beta in human fetal prostate

PURPOSE: We examined the immunolocalization of estrogen receptor (ER)alpha and ERbeta in the human fetal prostate. MATERIALS AND METHODS: Tissue sections from human fetal prostates at 7 to 22 weeks of gestation were stained with antibodies to ERalpha, ERbeta, and cytokeratin 10 and 14. RESULTS: ERalpha expression was not detected until 15 weeks of gestation with sparse staining in the utricle. By 19 weeks increased ERalpha expression was seen in the luminal cells of the ventral urogenital epithelium (UGE), basal cells of the dorsal UGE, utricle, distal periurethral ducts, peripheral stroma and posterior prostatic duct. K14 was detected in basal cells of the UGE and in several posterior acini. At 22 weeks ERalpha expression was more intense in all of these areas. ERbeta was expressed throughout the UGE, ejaculatory ducts, müllerian ducts and entire stroma at 7 weeks. Intense ERbeta staining was observed in these areas and in the prostatic buds by 8 weeks with persistent intense staining through 22 weeks. CONCLUSIONS: To our knowledge we report the first immunolocalization of ERalpha in the human fetal prostate and the earliest demonstration of ERbeta expression in the prostate at 7 weeks of gestation. ERbeta expression is intense during ductal morphogenesis, suggesting a role in normal glandular growth and proliferation. The induction of squamous metaplasia in the UGE, distal periurethral ducts and utricle is associated with ERalpha expression in these areas, while the induction of squamous metaplasia in peripheral prostatic acini is associated with peripheral stromal ERalpha expression. This study suggests estrogen signaling pathways in the human fetal prostate via ERalpha that involve epithelial-epithelial and epithelial-stromal interactions.     

Antiestrogens and selective estrogen receptor modulators reduce prostate cancer risk

The development of chemoprevention strategies against prostate cancer would have the greatest overall impact both medically and economically against prostate cancer. Estrogens are required for prostate carcinogenesis. Estrogenic stimulation through estrogen receptor alpha in a milieu of decreasing androgens contributes significantly to the genesis of benign prostatic hyperplasia, prostate dysplasia, and prostate cancer. The ability of antiestrogens and selective estrogen receptor modulators (SERMs) to delay and to suppress prostate carcinogenesis is supported by preclinical, clinical, and epidemiological studies. SERMs have many features that make them attractive candidates for prostate cancer chemoprevention including their favorable safety profile and efficacy in preclinical prostate cancer models. The true clinical benefits of SERMs for chemoprevention to prevent prostate cancer, however, should continue to be investigated through human clinical trials. A phase IIb/III human clinical trial is currently evaluating safety and efficacy of toremifene, a SERM, in men who have high-grade prostatic intraepithelial neoplasia.     

Androgen receptor mRNA detection in the human foetal prostate

In order to get an insight into androgen-mediated differentiation and development of the prostate, we detected the androgen receptor (AR) mRNA in the urogenital sinus of human foetuses at 12 and 16 weeks of gestation. Cytoplasmic dot hybridization using radiolabelled cDNA probe for human androgen receptor (AR) was performed. The AR mRNA could be detected at 12 weeks of gestation and its level was higher at 16 weeks of gestation.     

前列腺增生组织中白细胞介素-6受体基因表达水平的检测及其意义

应用逆转录聚合酶链反应方法定量检测了10例正常人前列腺、20例前列腺增生（BPH）组织及前列腺癌细胞系PC－3m中80ku白细胞介素－6受体（IL－6R）基因表达水平。结果发现正常前列腺组织中IL－6RmRNA呈低水平表达，而43PH组织中表达增强，明显高于正常组（P＜0．01），表明BPH发生与IL－6及其受体有关。此外，还发现55．0％（11／20）BPH组织中IL－6RmRNA含量高于前列腺癌细胞系PC－3m，提示IL－6所介导的融合毒素可能成为治疗BPH新的有效途径。     

类固醇受体辅活化子-1和核受体辅阻遏子在雄激素非依赖性前列腺癌的表达及临床意义

目的 探讨类固醇受体辅活化子-1（SRC-1）、核受体辅阻遏子（NCoR）在雄激素非依赖性前列腺癌（AIPC）的表达及临床意义。方法 采用免疫组化法检测20例激素依赖性前列腺癌（ADPC）、15例AIPC组织AR、SRC-1及NCoR表达。结果 1例AIPC无AR表达，其余AIPC及ADPC高表达AR。AIPC、ADPC均检测到SRC-1表达。SRC-1在AIPC的阳性率较ADPC组织明显升高（P〈0．01）。NCoR在AIPC、ADPC均有表达，但在AIPC的表达则出现明显降低（P〈0．01）。结论 SRC-1在AIPC表达升高和／或NCoR在AIPC表达降低引起的AR异常活化可能与前列腺癌（Pca）的进展有关。     

Androgen receptor or estrogen receptor-beta blockade alters DHEA-, DHT-, and E(2)-induced proliferation and PSA production in human prostate cancer cells

BACKGROUND: Dehydroepiandrosterone (DHEA) is an endogenous steroid that is metabolized to androgens and/or estrogens in the human prostate. DHEA levels decline with age, and use of DHEA supplements to retard the aging process is of unproved effectiveness and safety. LNCaP and LAPC-4 prostate cancer cells were used to determine whether DHEA-modulated proliferation and prostate specific antigen (PSA) production were mediated via the androgen receptor (AR) and/or ERbeta. METHODS: Cells were treated with DHEA, DHT, or E(2) and antagonists to AR (Casodex-bicalutamide) or ER (ICI 182,780) or siRNA to the respective receptors. Proliferation was assessed by MTT assay and PSA mRNA and protein secretion were measured by quantitative real-time PCR and ELISA. Associations of AR and ERbeta were analyzed by co-immunoprecipitation studies and fluorescent confocal microscopy. RESULTS: DHEA-, T-, and E(2)-induced proliferation of LNCaP cells was blunted by Casodex but not by ICI treatment. In LNCaP cells, Casodex and ICI suppressed hormone-induced PSA production. In LAPC-4 cells, DHT-stimulated PSA mRNA was inhibited by Casodex and ICI, and the minimal stimulation by DHEA was inhibited by ICI. Use of siRNAs confirmed involvement of AR and ERbeta in hormone-induced PSA production while AR-ERbeta co-association was suggested by immunoprecipitation and nuclear co-localization. CONCLUSIONS: These findings support involvement of both AR and ERbeta in mediating DHEA-, DHT-, and E(2)-induced PSA expression in prostate cancer cells.