Cellular changes in boric acid-treated DU-145 prostate cancer cells

Epidemiological, animal, and cell culture studies have identified boron as a chemopreventative agent in prostate cancer. The present objective was to identify boron-induced changes in the DU-145 human prostate cancer cell line. We show that prolonged exposure to pharmacologically-relevant levels of boric acid, the naturally occurring form of boron circulating in human plasma, induces the following morphological changes in cells: increases in granularity and intracellular vesicle content, enhanced cell spreading and decreased cell volume. Documented increases in beta-galactosidase activity suggest that boric acid induces conversion to a senescent-like cellular phenotype. Boric acid also causes a dose-dependent reduction in cyclins A-E, as well as MAPK proteins, suggesting their contribution to proliferative inhibition. Furthermore, treated cells display reduced adhesion, migration and invasion potential, along with F-actin changes indicative of reduced metastatic potential. Finally, the observation of media acidosis in treated cells correlated with an accumulation of lysosome-associated membrane protein type 2 (LAMP-2)-negative acidic compartments. The challenge of future studies will be to identify the underlying mechanism responsible for the observed cellular responses to this natural blood constituent.     

New EGF-R selective tyrosine kinase inhibitor reveals variable growth responses in prostate carcinoma cell lines PC-3 and DU-145

The effect of an EGF-R selective tyrosine kinase inhibitor ZM252868 was evaluated on the proliferation of PC-3 and DU-145 prostate cancer cell lines, which are purported to utilize an EGF-R-mediated autocrine pathway for regulation of cell growth. Basal growth of DU-145 cells was inhibited in a dose-dependent manner by the inhibitor, showing a 70% reduction at 1 μM, whilst the growth of PC-3 cells was not affected at this concentration. In the presence of 0.1 μM inhibitor, EGF and TGFα-stimulated DU-145 cell growth was decreased to below basal levels, while only TGFα-stimulated PC-3 cell growth was inhibited at a 1-μM concentration. Any growth responses to aFGF, bFGF, KGF, IGF1 and PDGF by DU-145 and PC-3 cells were unaffected by the inhibitor at concentrations of 1 μM or less. Additionally, the distribution of immunoreactive EGF-R varied between DU-145 and PC-3 cells, with EGF-R being predominately located on the cell membrane and in the cytoplasm, respectively. Int. J. Cancer 71:1010-1018, 1997. © 1997 Wiley-Liss Inc.     

Down-regulation of urokinase plasminogen activator and matrix metalloproteinases and up-regulation of their inhibitors by a novel nutrient mixture in human prostate cancer cell lines PC-3 and DU-145

Strong clinical and experimental evidence shows that elevated levels of urokinase plasminogen activators (u-PA) and matrix metalloproteinases (MMPs) are associated with prostate cancer progression, metastasis and shortened survival in patients. MMP activities are regulated by specific tissue inhibitors of metalloproteinases (TIMPs). A nutrient mixture (NM) containing lysine, proline, ascorbic acid and green tea extract showed anticancer activity against a number of cancer cell lines. Our main objective was to study the effect of NM on the activity of u-PA, MMPs and their inhibitor TIMPs on human prostate cancer cell lines PC-3 and DU-145. Human prostate cancer cell lines PC-3 and DU-145 (ATCC) were grown in MEM media with 10% FBS and antibiotics in 24?well tissue culture plates. At near confluence, the cells were treated with NM at 0-1000?μg/ml in triplicate at each concentration. Analysis of u-PA activity was carried out by fibrin zymography, MMPs by gelatinase zymography and TIMPs by reverse zymography. Both PC-3 and DU-145 prostate cancer cell lines demonstrated u-PA activity (subunits 1 and 2, corresponding to 35 and 33?kDa). Prostate cancer cell line PC-3 secretion of u-PA subunit 1 was decreased by 65% at NM 500?μg/ml and subunit 2 by 100% at NM 50?μg/ml. Prostate cancer cell line DU-145 secretion of u-PA subunit 1 was decreased by 97% at NM 500?μg/ml and subunit 2 by 100% at NM 100?μg/ml. Untreated PC-3 showed two bands for MMP-2 and MMP-9. NM inhibited their expression in a dose-dependent manner. The activity of MMP-2 and MMP-9 was significantly inhibited at 250?μg/ml with total inhibition at 500?μg/ml. DU-145 cells did not exhibit MMP activity. Activity of TIMPs was up-regulated in both prostate cancer cell lines in a dose-dependent manner. Minimum activity was expressed at 50?μg/ml NM and maximum at 1000?μg/ml. Correlation analyses revealed a positive correlation between u-PA and MMPs and a negative correlation between u-PA/MMPs and TIMPs. These results suggest NM as a potential anticancer agent since it targets invasive parameters of prostate cancer.     

环王巴明诱导DU145细胞凋亡的机制研究

目的：研究环王巴明诱导DU145细胞凋亡作用及其对Gli-1和Bcl-2 mRNA表达的影响,探讨环王巴明诱导DU145细胞凋亡的机制。方法：不同浓度环王巴明处理DU145细胞后,吖啶橙染色,荧光显微镜下观察细胞形态变化。流式细胞术观察细胞凋亡率变化,RT—PCR检测5、10μmol／L环王巴明作用72h后的实验组和对照组Gli-1、Bcl-2mRNA表达水平差异。结果：当环王巴明浓度大于5μmol／L作用72h后,荧光显微镜下可见细胞核固缩或碎裂,核仁变形等典型的凋亡形态学改变。环王巴明5μmol／L组Gli-1、Bcl-2 mRNA表达减弱,但同对照组差异无统计学意义（P〉0．05）,与空白及DMSO对照组相比10μmol／L环王巴明可以显著下调Gli—1、Bcl-2 mRNA表达（P〈0．01）。结论：环王巴明可诱导人前列腺癌DU145细胞株凋亡,其作用机制可能与下调Gli-1和Bcl-2 mRNA表达,活化细胞凋亡的线粒体途径有关。     

环王巴明诱导DU145细胞凋亡的机制研究

目的:研究环王巴明诱导DU145细胞凋亡作用及其对Gli-1和Bcl-2 mRNA表达的影响,探讨环王巴明诱导DU145细胞凋亡的机制.方法:不同浓度环王巴明处理DU145细胞后,吖啶橙染色,荧光显微镜下观察细胞形态变化.流式细胞术观察细胞凋亡率变化,RT-PCR检测5、10μmol/L环王巴明作用72h后的实验组和对照组Gli-1、Bcl-2 mRNA表达水平差异.结果:当环王巴明浓度大于5μmol/L作用72h后,荧光显微镜下可见细胞核固缩或碎裂,核仁变形等典型的凋亡形态学改变.环王巴明5μmol/L组Gli-1、Bcl-2mRNA表达减弱,但同对照组差异无统计学意义(P>0.05),与空白及DMSO对照组相比10μmol/L环王巴明可以显著下调Gli-1、Bcl-2 mRNA表达(P<0.01).结论:环王巴明可诱导人前列腺癌DU145细胞株凋亡,其作用机制可能与下调Gli-1和Bcl-2mRNA表达,活化细胞凋亡的线粒体途径有关.     

miR-143 and miR-145 inhibit stem cell characteristics of PC-3 prostate cancer cells

Emerging evidence demonstrates that cancer stem cells (CSCs) are the critical drivers of tumor progression and metastasis. The microRNAs (miRNAs) may play a crucial role in repressing/promoting metastasis of cancer by regulating CSCs. A previous study showed that miR-143 and miR-145 play an important role in regulating bone metastasis of prostate cancer (PCa), but the exact mechanism of regulation of bone metastasis of PCa is not fully understood. In this study, we found that overexpression of miR-143 and miR-145 inhibited the cell viability and colony formation of PC-3 cells from PCa bone metastasis. Furthermore, miR-143 and miR-145 suppressed tumor sphere formation and expression of CSC markers and 'stemness' factors including CD133, CD44, Oct4, c-Myc and Klf4 in PC-3 cells. The study further found that miR-143 and miR-145 inhibit bone invasion and tumorigenicity of PC-3 cells in vivo. Collectively, these findings demonstrate that miR-143 and miR-145 inhibit CSC properties of PC-3 cells and suggest that miR-143 and miR-145 may play a significant role in the bone metastasis progression of PCa by regulating CSC characteristics.     

Fenofibrate attenuates contact-stimulated cell motility and gap junctional coupling in DU-145 human prostate cancer cell populations

In the present study, we investigated the effects of fenofibrate on the invasive potential of DU-145 human prostate cancer cells in the context of gap junctional intercellular coupling and the formation of reactive oxygen species. Time-lapse analyses of cell motility, accompanied by tests of cell viability, membrane microviscosity, reactive oxygen species accumulation and the function of gap junctional protein connexin 43 were performed in monolayer cultures of DU-145 cells following fenofibrate administration. Fenofibrate inhibited the motility of DU-145 cells and attenuated gap junctional intercellular coupling in a manner independent of its effects on cell viability, PPARα activation and cell membrane micro-viscosity. Instead, N-acetyl-L-cysteine, a scavenger of reactive oxygen species, restored cell motility and gap junctional coupling in fenofibrate-treated DU-145 cell populations. These data indicate that two parameters crucial for cancer cell metastatic potential, i.e. cell motility and gap junctional coupling, are inhibited by fenofibrate. Thus, fenofibrate affects prostate cancer cell invasion via an orchestrated action on versatile cancer cell properties determining this process. A novel mechanism of anti-invasive activity of fenofibrate, which depends on its interference with cell motility and the function of gap junctions regulated by reactive oxygen species, is suggested.     

新生霉素诱导前列腺癌PC-3细胞自噬的研究

目的:通过体外细胞实验,观察新生霉素是否抑制了前列腺癌PC-3细胞的增殖,并在分子水平和形态学上证实新生霉素通过细胞自噬抑制了前列腺癌PC-3细胞的增殖.为新生霉素应用于去势抵抗性前列腺癌(castration-resistant prostate cancer,CRPC)的临床治疗提供理论和实验依据.方法:设置对照组和不同浓度的新生霉素实验组,作用前列腺癌PC-3细胞24小时后,利用MTT法测定对照组和不同浓度实验组的增殖率,并计算出新生霉素的半抑制率.透射电镜观察对照组及实验组细胞内的自噬体.利用免疫荧光技术,在荧光显微镜下观察对照组和不同浓度实验组发生细胞自噬时的自噬标志性蛋白LC-3Ⅱ和自噬底物蛋白p62的不同.利用RT-PCR在mRNA水平上检测对照组和不同浓度实验组的自噬相关基因LC-3Ⅱ、Beclin-1的表达.结果:MTT结果示新生霉素能使PC-3细胞的增殖明显受到抑制(F=569.26,P=0.000),其抑制率随着药物浓度的增加而增加,根据公式计算出其IC50=1.52mmol/L.透射电镜观察可见实验组PC-3细胞质内自噬体和自噬溶酶体数量较对照组多,且随着浓度的增加自噬体数量增加.自噬体在细胞中的分布通过绿色荧光FITC标记的自噬特异性蛋白LC-3Ⅱ在荧光显微镜下清晰显示,在细胞膜附近有绿色荧光呈散点状分布,随着实验组新生霉素浓度的增加荧光强度增加.而绿色荧光FITC标记的自噬底物蛋白p62在荧光显微镜下的强度随着药物浓度的增加而降低.RT-PCR在mRNA水平上检测到随着药物浓度的增加自噬相关基因LC-3Ⅱ、Beclin-1的表达量升高.结论:在体外细胞实验中,新生霉素能够在一定浓度范围内呈浓度依赖性的抑制PC-3细胞增殖.新生霉素能在mRNA水平上增强Beclin-1、LC-3Ⅱ的表达.新生霉素可能是通过诱导细胞自噬性死亡来抑制前列癌PC-3细胞的增殖.     

Genistein,a soy isoflavone,induces glutathione peroxidase in the human prostate cancer cell lines LNCaP and PC-3

Treatment of malignant brain tumors remains a clinical challenge. New treatment modalities are under investigation and among these are intratumoral infusion of immunotoxins that bind to specific cell surface molecules on the malignant cells. We have compared the efficacy of the 425.3-PE immunotoxin (which targets the epidermal growth factor [EGF] receptor) with the well-known immunotoxin Tfn-CRM107 (which targets the transferrin receptor), for the treatment of subcutaneous and intracranial human gliomas in nude animals. Bolus intratumoral administration of 1 microg Tfn-CRM107 or 425.3-PE into sc U87Mg tumors in nude mice reduced the tumor volume to 29 and 79%, respectively, of that in the control group 18 days after start of treatment. Higher doses of Tfn-CRM107 were toxic to the animals, whereas 425.3-PE was tolerated, with a dose-response relationship of up to 8 microg, a dose that reduced the tumor volume to 2% of control. In nude rats, treatment of intracerebral U87Mg tumors with Tfn-CRM107 proved ineffective and doses above 10 ng/animal were toxic to tumor-bearing rats. In contrast, intratumoral administration of 4 microg 425.3-PE increased symptom-free survival from 23 days to 40 days, with 2/9 surviving more than 90 days. We have recently shown that immunodeficient rats inoculated intracerebrally with precultured glioblastoma biopsy specimens develop highly infiltrative brain tumors. Direct interstitial infusion of immunotoxins into such tumors reduced the number of animals with detectable tumors at autopsy after 3 months, from 8/9 in the control animals to 4/6 and 2/6 in animals treated with Tfn-CRM107 and 425.3-PE, respectively. In conclusion, the anti-EGF receptor immunotoxin 425.3-PE exhibited promising efficacy, comparable to or better than that of Tfn-CRM107, an immunotoxin that in early clinical trials has been found to give responses in patients with brain tumors.     

Differential expression of integrin subunits in DU-145/AR prostate cancer cells

We have established a clonal DU-145 prostate cancer cell line (DU-145/AR) stably transfected with androgen receptor cDNA. We investigated the expression of integrin subunits, adhesion to extracellular matrices, the invasion of DU-145/AR prostate cancer cells. The expression of various integrin subunits and adhesion to various extracellular matrices in DU-145, DU-145/Neo and DU-145/AR cells were examined. The haptoinvasion and the haptotactic migration of these cells were investigated using a Transwell cell culture chamber assay. DU-145/AR cells exhibited lower expression of alpha6 and beta4 integrin subunits and higher expression of alpha2 and alpha5 than DU-145 cells. DU-145/AR cells showed significantly lower adhesion to fibronectin, laminin-1 and laminin-5 than DU-145/ Neo cells, whereas DU-145/AR cells showed higher adhesion to type I and type IV collagen. Haptoinvasion of DU-145/AR cells into Matrigel/fibronectin-coated filter was significantly reduced as compared with DU-145/Neo or DU-145 cells, but there was no significant difference between DU-145/AR and control cells in the haptotactic migration to fibronectin. Dihydrotestosterone (DHT) inhibited the invasive ability of DU-145/AR cells. These results indicate that androgen receptor may play a role in the regulation of adhesion to the extracellular matrices and invasion of prostate cancer cells through influencing the expression of specific integrin subunits.     

Inhibition of human androgen-independent PC-3 and DU-145 prostate cancers by antagonists of bombesin and growth hormone releasing hormone is linked to PKC, MAPK and c-jun intracellular signalling

Bombesin/gastrin-releasing peptide (BN/GRP) antagonists RC-3940-II and RC-3940-Et, and growth hormone-releasing hormone (GHRH) antagonists MZ-J-7-118 and RC-J-29-18 inhibit the growth of human androgen-independent PC-3 and DU-145 prostate cancers in nude mice. Additive inhibitory effects were observed after treatment with both classes of analogs. In the present study, we investigated the effects of these antagonists on intracellular signalling pathways of protein kinase C (PKC), mitogen activated protein kinases (MAPK) and c-fos and c-jun oncogenes that are involved in tumour cell proliferation. In PC-3 tumours, antagonists of BN/GRP and GHRH decreased significantly the expression of PKC isoforms alpha (alpha), eta (eta) and zeta (zeta) and increased that of delta (delta) PKC protein. MAPK was not detectable. In DU-145 tumours, which constitutively express MAPK, all treatments strongly decreased the levels of p42/44 MAPK. Treatment with the antagonists tended to reduce m-RNA for c-jun in both tumour models. In proliferation assays in vitro, inhibitors of PKC and MAPK diminished growth of DU-145 and PC-3 cells. These findings suggest that antagonists of BN/GRP and GHRH inhibit the growth of androgen-independent prostate cancer by affecting intracellular signalling mechanisms of PKC, MAPK and c-jun.     

RhoC GTPase is required for PC-3 prostate cancer cell invasion but not motility

It is projected that in 2005, approximately 220 900 men will be newly diagnosed with carcinoma of the prostate (CaP). Men who are diagnosed with locally advanced or metastatic disease undergo androgen ablation therapy and most will relapse and progress within 18 months. Metastasis to bone is the major clinical concern during CaP progression, as it is associated with intractable pain, bone fracture and paralysis resulting from spinal cord compression. Therefore, an understanding of the key mechanisms involved in CaP cell bone metastasis is vital to development of novel treatments. The Rho GTPases are molecular switches involved in cell survival, motility and invasion. Increased expression of RhoC GTPase is linked to enhanced metastatic potential in multiple cancers; however, the role of RhoC GTPase in CaP metastasis has not been addressed. In the current study, we demonstrate that RhoC GTPase is expressed and active in PC-3 CaP cells. RhoC inhibition, either pharmacologically with C3 exotransferase or molecularly through expression of a dominant-negative RhoC, promotes IGF-I stimulated random motility but decreases in vitro invasion and experimental metastases. Inhibition of RhoC activity results in drastic morphologic changes and alterations in the expression and distribution of focal adhesion-related proteins. These data suggest that RhoC inhibition leads to activation of other GTPases involved in nondirected motility and that expression of active RhoC is required for the invasive phenotype of PC-3 cells.     

波形蛋白对前列腺癌细胞侵袭与转移的影响

背景与目的:波形蛋白(vimentin)是一种细胞骨架蛋白,参与调节细胞的运动和增殖。本研究通过检测波形蛋白在前列腺癌细胞系中的表达,探讨其对前列腺癌细胞侵袭与转移的影响。方法:应用二维电泳-质谱分析(two-dimensionalgel electrophoresis matrix-assisted laser desorption/time of flight mass spectrometry,2-DE MALDI TOF-MS)检测波形蛋白在前列腺癌配对细胞系中的差异表达,用基因干预技术结合体外侵袭实验探讨波形蛋白对细胞侵袭能力的影响。结果:波形蛋白在前列腺癌高转移细胞系PC-3M-1E8中的表达高于低转移细胞系PC-3M-2B4中的表达。成功构建波形蛋白反义真核表达载体和正义真核表达载体,分别转染PC-3M-1E8和PC-3M-2B4细胞,转染波形蛋白反义真核表达载体的细胞(PC-3M-1E8/vas)的穿膜细胞数为99.3±4.8,明显低于空质粒对照组细胞[PC-3M-1E8/3.1(-)]的319.4±6.5(P<0.01);转染波形蛋白正义真核表达载体的细胞(PC-3M-2B4/vs)的穿膜细胞数为330.5±5.8,明显高于空质粒对照组细胞[PC-3M-2B4/3.1( )]的98.6±7.5(P<0.01)。结论:波形蛋白高表达可促进前列腺癌细胞的侵袭与转移。     

Curcumin confers radiosensitizing effect in prostate cancer cell line PC-3

Curcumin (Diferuloylmethane) is a major chemical component of turmeric (curcuma longa) and is used as a spice to give a specific flavor and yellow color in Asian food. Curcumin exhibits growth inhibitory effects in a broad range of tumors as well as in TPA-induced skin tumors in mice. This study was undertaken to investigate the radiosensitizing effects of curcumin in p53 mutant prostate cancer cell line PC-3. Compared to cells that were irradiated alone (SF(2)=0.635; D(0)=231 cGy), curcumin at 2 and 4 microM concentrations in combination with radiation showed significant enhancement to radiation-induced clonogenic inhibition (SF(2)=0.224: D(0)=97 cGy and SF(2)=0.080: D(0)=38 cGy) and apoptosis. It has been reported that curcumin inhibits TNF-alpha-induced NFkappaB activity that is essential for Bcl-2 protein induction. In PC-3 cells, radiation upregulated TNF-alpha protein leading to an increase in NFkappaB activity resulting in the induction of Bcl-2 protein. However, curcumin in combination with radiation treated showed inhibition of TNF-alpha-mediated NFkappaB activity resulting in bcl-2 protein downregulation. Bax protein levels remained constant in these cells after radiation or curcumin plus radiation treatments. However, the downregulation of Bcl-2 and no changes in Bax protein levels in curcumin plus radiation-treated PC-3 cells, together, altered the Bcl2 : Bax ratio and this caused the enhanced radiosensitization effect. In addition, significant activation of cytochrome c and caspase-9 and -3 were observed in curcumin plus radiation treatments. Together, these mechanisms strongly suggest that the natural compound curcumin is a potent radiosesitizer, and it acts by overcoming the effects of radiation-induced prosurvival gene expression in prostate cancer.     

Mitochondrial DNA determines androgen dependence in prostate cancer cell lines

Prostate cancer progresses from an androgen-dependent to androgen-independent stage after androgen ablation therapy. Mitochondrial DNA plays a role in cell death and metastatic competence. Further, heteroplasmic large-deletion mitochondrial DNA is very common in prostate cancer. To investigate the role of mitochondrial DNA in androgen dependence of prostate cancers, we tested the changes of normal and deleted mitochondrial DNA in accordance with the progression of prostate cancer. We demonstrated that the androgen-independent cell line C4-2, established by inoculation of the androgen-dependent LNCaP cell line into castrated mice, has a greatly reduced amount of normal mitochondrial DNA and an accumulation of large-deletion DNA. Strikingly, the depletion of mitochondrial DNA from androgen-dependent LNCaP resulted in a loss of androgen dependence. Reconstitution of normal mitochondrial DNA to the mitochondrial DNA-depleted clone restored androgen dependence. These results indicate that mitochondrial DNA determines androgen dependence of prostate cancer cell lines. Further, mitochondrial DNA-deficient cells formed tumors in castrated athymic mice, whereas LNCaP did not. The accumulation of large deletion and depletion of mitochondrial DNA may thus play a role in the development of androgen independence, leading to progression of prostate cancers.     

Reduction of 9-nitrocamptothecin-triggered apoptosis in DU-145 human prostate cancer cells by ectopic expression of 14-3-3zeta

A promising family of anticancer agents, the camptothecins, is noted for their ability to induce apoptosis specifically in malignant cells. However, a major obstacle for successful cancer treatment by these and other chemotherapeutic agents is the intrinsic or acquired resistance to drug treatment. Resistance to 9NC6, a camptothecin derivative, has been modeled in vitro using a human prostate cancer cell line. To elucidate the mechanism for acquired 9NC resistance, we have used a subtractive cloning approach to identify genes whose altered expression level is reflective of 9NC resistance or susceptibility. Differential gene expression was compared between wild-type human prostate cancer cell line, DU-145, and a 9NC-resistant subline, RC1. Results were confirmed by Northern and Western blot analyses. In this report, we focus on one gene, 14-3-3zeta. An expression vector of a full-length myc-epitope-tagged 14-3-3zeta cDNA was constructed and used for transfection into DU-145 cells. We consistently observed that 14-3-3zeta message and protein levels were dramatically increased in 9NC resistant cells. The expression levels of other 14-3-3 family members were unaffected. Strikingly, ectopic overexpression of 14-3-3zeta in wild-type 9NC-susceptible prostate cancer cells decreased 9NC-induced apoptosis. Our results suggest a novel direct or indirect role of 14-3-3zeta in mediating resistance of DU-145 cells to the topoisomerase I inhibitor, 9NC. We are currently exploring whether this represents a more general pathway for drug resistance as well.     

Polymorphisms in estrogen bioactivation, detoxification and oxidative DNA base excision repair genes and prostate cancer risk

To date, the potential impact of hormones on prostate cancer has predominantly focused on receptor-mediated events. However, catechol estrogens, if not inactivated by catechol-O-methyltransferase (COMT), can generate large quantities of reactive oxygen species (ROS). ROS may cause a spectrum of damage including oxidative DNA base lesions, which can lead to irreversible mutation(s) if they are not repaired by base excision repair (BER) systems. hOGG1 is a key enzyme in short patch BER because it recognizes and performs initial excision of the most common form of oxidative DNA base damage, 8-hydroxyguanine (8-oxo-dG). To investigate potential non-receptor-mediated estrogen effects, we evaluated the association between COMT Val158Met and hOGG1 Ser326Cys polymorphisms and prostate cancer in a family-based case-control study (439 prostate cancer cases, 479 brother controls). We observed no noteworthy associations between these polymorphisms and prostate cancer risk in the total study population. However, among men with more aggressive prostate cancer, the hOGG1 326 Cys/Cys genotype was inversely associated with disease (OR=0.30; 95% CI=0.09-0.98). Combining the lower activity CYP1B1 432 Leu/Leu or Leu/Val genotypes (which may decrease the level of catechol estrogens and ROS generated) with the hOGG1 326 Cys/Cys genotype and the XRCC1 399 Arg/Arg or Arg/Gln genotypes (which may enhance BER) resulted in an even further reduced risk in Caucasians with more aggressive disease (OR=0.09; 95% CI=0.01-0.56). Including the high-activity COMT 158Val allele to this combination also lowered aggressive prostate cancer risk but the effect was not as strong (OR=0.20; 95% CI=0.05-0.88). The decreased risk we observed with the hOGG1 326 Cys/Cys genotype confirms an earlier report and the further reduced risk found with the CYP1B1 (432 Leu/Leu or Leu/Val)-hOGG1 (326 Cys/Cys)-XRCC1 (Arg/Arg or Arg/Gln) genotype combination may lend new insights to the importance of ROS generated from non-receptor-mediated estrogenic mechanisms in more aggressive prostate cancer.     

MicroRNA-145 is regulated by DNA methylation and p53 gene mutation in prostate cancer

MiR-145 is downregulated in various cancers including prostate cancer. However, the underlying mechanisms of miR-145 downregulation are not fully understood. Here, we reported that miR-145 was silenced through DNA hypermethylation and p53 mutation status in laser capture microdissected (LCM) prostate cancer and matched adjacent normal tissues. In 22 of 27 (81%) prostate tissues, miR-145 was significantly downregulated in the cancer compared with the normal tissues. Further studies on miR-145 downregulation mechanism showed that miR-145 is methylated at the promoter region in both prostate cancer tissues and 50 different types of cancer cell lines. In seven cancer cell lines with miR-145 hypermethylation, 5-aza-2'-deoxycytidine treatment dramatically induced miR-145 expression. Interestingly, we also found a significant correlation between miR-145 expression and the status of p53 gene in both LCM prostate tissues and 47 cancer cell lines. In 29 cell lines with mutant p53, miR-145 levels were downregulated in 28 lines (97%), whereas in 18 cell lines with wild-type p53 (WT p53), miR-145 levels were downregulated in only 6 lines (33%, P < 0.001). Electrophoretic mobility shift assay showed that p53 binds to the p53 response element upstream of miR-145, but the binding was inhibited by hypermethylation. To further confirm that p53 binding to miR-145 could regulate miR-145 expression, we transfected WT p53 and MUT p53 into PC-3 cells and found that miR-145 is upregulated by WT p53 but not with MUTp53. The apoptotic cells are increased after WT p53 transfection. In summary, this is the first report documenting that downregulation of miR-145 is through DNA methylation and p53 mutation pathways in prostate cancer.