Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0376358 (prostate cancer)
 59,338 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated the role of androgen-induced oxidative stress in prostate cancer using the androgen-responsive LNCaP human prostate cancer cell line exposed to a 1-nM concentration of the synthetic androgen R1881 (which correlates with serum androgen levels). Such exposure, which decreases growth rate and increases oxidative stress in LNCaP cells, induced statistically significant mitochondrial changes. A 40% increase in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) reduction, indicative of mitochondrial dehydrogenase activity, occurred 24 hr after androgen treatment. This change preceded 50-110% increases, 40-96 hr after R1881 exposure, in levels of cellular peroxides and hydroxyl radicals as measured by 2'7'-dicholorofluorescin diacetate (DCF) fluorescence. On the basis of electron microscopy measurements, R1881 treatment increased the area fraction of mitochondria per cell by approximately 100% at 72 hr. In agreement, mitochondrial mass at 96 hr, evaluated by the fluorescent dye nonyl acridine orange (NAO), was 80% higher in treated cells. R1881 exposure for 24 hr lowered the activities of electron transport system (ETS) complexes, I, II, and IV by 17-27% and ATP levels by 50%. The ETS inhibitors, rotenone and antimycin A, lowered androgen-induced DCF fluorescence readings to control levels thereby suggesting ETS involvement in androgen-induced oxidant production. Addition of alpha-tocopherol succinate abrogated R1881-induced elevations in MTT reduction. In sum, androgens may, directly or indirectly, contribute to oxidative stress in LNCaP cells by regulating mitochondrial number, activity, and oxidant production by mechanisms that are, at least in part, sensitive to an antioxidant.
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PMID:Androgen-induced oxidative stress in human LNCaP prostate cancer cells is associated with multiple mitochondrial modifications. 1122 34

Tissue-specific transcriptional regulatory elements can increase the safety of gene therapy vectors. Unlike prostate-specific antigen (PSA/hK3), whose expression displays an inverse correlation with prostate cancer grade and stage, human glandular kallikrein 2 (hK2) is upregulated in higher grade and stage disease. Therefore, our goal was to develop a strong and prostate-specific hK2-based promoter for targeted gene therapy. We identified the minimum "full-strength" hK2 enhancer and built transcriptional regulatory elements composed of multiple tandem copies of this 1.2-kb enhancer, fused to the hK2 minimal promoter. Relative to the weak induction of the minimal hK2 promoter by androgen analog (R1881) in androgen receptor (AR)-positive LNCaP cells, transcriptional activity was increased by 25-, 44-, 81-, and 114-fold when one to four enhancers were spliced to the hK2 promoter, respectively. In contrast, the enhancer/promoter elements were inactive in the AR(-) prostate cancer line PC-3 and in a panel of nonprostate lines, including 293, U87, MCF-7, HuH-7, and HeLa cells. Furthermore, we generated a recombinant adenovirus, ADV.hK2-E3/P-EGFP, expressing enhanced green fluorescent protein (EGFP) under the control of the hK2 triplicate enhancer/promoter, and compared its properties with ADV.CMV-EGFP expressing EGFP under the control of the cytomegalovirus (CMV) enhancer/promoter. Unlike the CMV promoter, the hK2-E3/P promoter was at least 100-fold inducible by R1881 in the adenoviral backbone. Compared with in situ injection of subcutaneous LNCaP tumors with ADV.CMV-EGFP, which led to detectable EGFP expression in tumor, liver, and brain tissue, ADV.hK2-E3/P-EGFP injection led to robust but tumor-restricted EGFP expression. These results suggest that the hk2 multienhancer/promoter should be a powerful novel reagent for safer targeted gene therapy of prostate cancer.
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PMID:Robust prostate-specific expression for targeted gene therapy based on the human kallikrein 2 promoter. 1126 87

Quantitative expression profile of androgen-regulated genes (ARGs) was evaluated in the hormone-responsive prostate cancer cell line LNCaP by serial analysis of gene expression (SAGE). A total of 83,489 SAGE tags representing 23,448 known genes or expressed sequence tags (ESTs) and 1,655 potentially novel sequences have unraveled the transcriptome of LNCaP cells, the most common cell line used in prostate cancer research. Comparison of transcripts between control and R1881-treated LNCaP cells revealed the induction of 136 genes and repression of 215 genes in response to androgen (p < 0.05). Strikingly, a high fraction ( approximately 90%) of ARGs identified in our study has not been described as ARGs previously. A number of prostate-specific transcription factors were among the ARGs identified here. Classification of the ARGs on the basis of biochemical functions revealed that a great majority of ARGs identified in our experimental system appear to be involved in regulation of transcription, splicing, ribosomal biogenesis, mitogenesis, bioenergetics and redox processes. One of the novel aspects of androgen signaling included androgen regulation of genes involved in DNA repair/recombination process. By comparing our LNCaP-C and LNCaP-T SAGE libraries with SAGE tag libraries available at the NCBI-SAGE website, we have identified >200 potential prostate specific/abundant transcripts. The discovery of new prostate-specific genes and ARGs provides a unique opportunity to determine the role of these genes in prostate cell growth, differentiation and tumorigenesis.
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PMID:Quantitative expression profile of androgen-regulated genes in prostate cancer cells and identification of prostate-specific genes. 1129 Oct 65

The androgen-signaling pathway plays a critical role in prostate cancer development and progression. We have recently demonstrated that the Wilms' tumor suppressor gene product, WT1, binds to multiple sites in the androgen receptor (AR) promoter and transcriptionally represses the AR gene promoter in vitro. We asked whether WT1 repression of the endogenous AR gene interferes in the androgen signal transduction cascade and modifies AR target gene expression. We analyzed the effect of WT1 (-/-) overexpression on an AR target gene reporter construct that contains the luciferase gene, the ElB TATA box, and two copies of the androgen-response element (ARE), the dimeric AR binding site. Luciferase activity was determined in 293 kidney and TM4 Sertoli cells, two nontumorigenic cell lines that express both AR and WT1. Cells were cotransfected by lipofectamine in the presence or absence of the synthetic androgen R1881. Results showed that overexpression of WT1 downregulates ARE-reporter gene transcription in both cell lines tested. The inhibitory effect of WT1 on the AR target gene construct was dose-dependent and androgen-independent in 293 cells, whereas in TM4 cells it was androgen-dependent. Additionally, a zinc-finger mutant WT1 (-/-) expression construct, R394W, failed to decrease luciferase activity, suggesting that WT1 downregulates the ARE-reporter gene construct activity by directly repressing the endogenous AR gene promoter. Furthermore, we analyzed the expression of WT1 and AR mRNA in several prostate cancer cell lines in order to understand the role WT1 may play in prostate cancer development and progression. Gel analysis of cDNA amplified by RT-PCR of AR and WT1 RNA from prostate cancer and non-prostatic cell lines showed that LNCaP and MDAPCa2b, two metastatic prostate cancer cell lines which are androgen-sensitive, expressed AR but not WT1. Du145 and PC3, two cell lines from advanced metastatic prostate cancer, which are characterized as androgen-independent and -insensitive, did not express AR but expressed a high level of WT1. Two non-prostatic cell lines, T47D and 293, weakly co-expressed AR and WT1. This inverse relationship between AR and WT1 expression in prostate cancer cell lines, together with WT1 repression of the AR promoter, suggest a role for WT1 in the androgen signaling pathway and in prostate cancer development and progression.
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PMID:Transcriptional regulation of the androgen signaling pathway by the Wilms' tumor suppressor gene WT1. 1129 20

Androgens exert a peculiar biphasic dose-dependent influence on the proliferation of LNCaP cells, a widely used model to study androgen effects on prostate cancer cells. Low concentrations of androgen stimulate proliferation, but high concentrations inhibit proliferation and induce strong expression of differentiation markers. In order to gain more insight into the molecular mechanisms that underlie these changes we studied the influence of a wide concentration range of the synthetic androgen R1881 on several cell cycle- and differentiation-related parameters. Low concentrations (0.1 nM), known to promote LNCaP cell proliferation, induce an increase of Retinoblastoma protein phosphorylation, accompanied by an increase of E2F-1 protein levels and E2F activity and by increased expression of the E2F-target gene products E2F-1 and cyclin A. High concentrations of R1881 (10 nM) induce strong expression of the differentiation marker prostate-specific antigen. Retinoblastoma protein is largely hypophosphorylated, resulting in low E2F activity and low concentrations of E2F-1 and cyclin A mRNA. Finally, there is a strong increase of p27(KIP1) protein, but not of p27(KIP1) mRNA. These results indicate that the biphasic dose response of LNCaP proliferation to androgen is closely reflected in Rb phosphorylation, E2F activity and p27(KIP1) protein expression.
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PMID:E2F activity is biphasically regulated by androgens in LNCaP cells. 1132 73

Androgen plays a critical role in the promotion and growth of prostate cancer. Androgen ablation has an expanding role in prostate cancer treatment and is now used to improve the efficacy of radiation therapy in addition to its role in treatment of metastatic disease. Here we show that androgen interferes with induction of prostate cancer cell death induced by a variety of stimuli. The effect of androgen on cell death occurs predominantly by interference with caspase activation and the inhibition of caspase cleavage in both the extrinsic and intrinsic cell death pathways. Androgen inhibited apoptosis induced by both tumor necrosis factor alpha (TNF-alpha) and by Fas activation with or without concomitant irradiation. An antiapoptotic effect was seen in the presence of R1881, dihydrotestosterone, and also 17beta-estradiol within 24 h of death induction. Sustained inhibition of apoptosis at 72 h was seen only with R1881, dihydrotestosterone, cyproterone acetate, and hydroxyflutamide. Androgen treatment inhibited activation of caspases-8, -7, and -9 by TNF-alpha +/- irradiation. Androgen attenuated BAX expression and blocked appearance of the proapoptotic p18 fragment of BAX. Androgen also abrogated BID cleavage induced by TNF-alpha + irradiation that contributed to a decrease in cytochrome c egress from mitochondria induced by TNF-alpha +/- irradiation. There was also decreased mitochondrial depolarization in response to TNF-alpha + irradiation. Production of the proapoptotic lipid metabolite ceramide was not affected by androgen, but androgen acted downstream from ceramide generation because R1881 blocked cell-death induction by bacterial sphingomyelinase. Inhibition of phosphoinositol-3-kinase activity by wortmannin induced apoptosis that was also blocked by androgen, but there was no effect on protein levels or phosphorylation of AKT, indicating that R1881 did not interact with survival signaling of phosphoinositol-3-kinase. Lastly, androgen inhibited activation of nuclear factor-kappaB during death induction, but the effect of androgen on cell death was not mediated by interference with the nuclear factor-kappaB pathway. The data suggest that androgen induced blockade of caspase activation in both intrinsic and extrinsic cell death pathways and thereby was able to protect prostate cancer cells from apoptosis induced by diverse stimuli.
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PMID:Androgen blocks apoptosis of hormone-dependent prostate cancer cells. 1145 15

Genes that are regulated by androgens in the human prostate are believed to play an essential role in prostate physiology and they may also be involved in the proliferative response of prostate cancer cells to androgens. We used a cDNA subtraction approach to identify novel androgen-regulated transcripts in LNCaP cells that were exposed to 0.1 nM R1881 for 24 h. We report here that SPAK, a recently identified STE20/SPS1-related kinase that modulates p38 MAP kinase activity, exhibited increased expression in androgen-treated LNCaP cells. Androgen regulation of SPAK was both dose- and time-dependent. R1881-induced SPAK expression was completely abrogated by the antiandrogen casodex and by actinomycin D indicating that androgen induction of SPAK requires the androgen receptor and transcription. Cycloheximide caused a partial inhibition of R1881-induced SPAK expression which suggests that androgen induction of SPAK expression may require synthesis of additional proteins. Northern blot and ribonuclease protection assays demonstrated that SPAK is expressed at high levels in normal human testes and prostate, as well as in a number of breast and prostate cancer cell lines. These results identify SPAK, a member of a key cell signalling pathway, as an androgen-responsive gene in LNCaP cells. We hypothesize that SPAK may mediate androgen action in the normal and cancerous prostate gland.
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PMID:Androgens induce expression of SPAK, a STE20/SPS1-related kinase, in LNCaP human prostate cancer cells. 1151 53

Clinical experience with suicide gene therapy for prostate cancer using first-generation approaches has provided a basis for developing improved strategies. Given the low proliferation rate exhibited by prostate cancer, one improvement would be to develop suicide genes that effectively kill both dividing and nondividing cells. A second improvement would be to restrict cytotoxicity to prostate cancer cells, limiting injury of nondiseased tissue. Here we describe a novel approach to achieving both goals based on: (a) the use of a small, but potent, prostate-specific composite promoter, ARR(2)PB, based on the rat probasin gene; and (b) the use of a powerful artificial death switch, called inducible caspase-9 (iCaspase-9). ARR(2)PB includes two copies of the androgen response region (ARR), each containing two androgen receptor (AR)-binding sites, placed upstream of the probasin promoter elements necessary for basal transcription. Because iCaspase-9 contains two binding sites for the dimeric ligand, AP20187, administration of chemical inducers of dimerization leads to aggregation and caspase activation, followed by rapid apoptosis in both dividing and nondividing cells. Using both reagents, we constructed two novel adenoviruses (ADVs), ADV.ARR(2)PB-iCasp9 expressing iCaspase-9 and control ADV.ARR(2)PB-EGFP expressing enhanced green fluorescent protein (EGFP). We demonstrate that tissue specificity is not sacrificed in an ADV backbone because the marker protein, EGFP, is expressed in R1881-stimulated ADV.ARR(2)PB-EGFP-transduced LNCaP cells but not in AR(-) PC-3, 293, HuH-7, U-87, and MCF-7 cells. Similarly, Pro-iCaspase-9 is expressed in ADV.ARR(2)PB-iCasp9-infected LNCaP cells after R1881 administration and is activated after AP20187 administration. In vitro experiments revealed rapid and efficient iCaspase-9-induced apoptosis of LNCaP cells in both an R1881- and AP20187-dependent manner. Only 28, 8, and 0.5% survival of LNCaP cells was seen at multiplicities of infection of 2, 10, and 25, respectively. Furthermore, at a multiplicity of infection of 10, extraordinary sensitivity to AP20187 was seen (IC(50), approximately 3 pM). In vivo experiments showed that ADV.ARR(2)PB-iCasp9 induced apoptosis in LNCaP but not in HuH-7 xenograft tumors in an AP20187-dependent manner. Furthermore, a simple i.p. injection of AP20187 dramatically suppressed LNCaP tumor growth in nude mice and led to a significantly increased host survival. This study demonstrates the feasibility of using tissue-specific expression of cell cycle-independent iCaspases as a nonmutagenic alternative modality for prostate cancer suicide gene therapy.
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PMID:Adenovirus-mediated tissue-targeted expression of a caspase-9-based artificial death switch for the treatment of prostate cancer. 1155 53

An androgen-independent (AI) prostate cancer cell line, derived recently from an LNCaP cell line maintained in androgen-poor conditions, has properties resembling a subgroup of advanced prostate cancers in that it has an overexpressed androgen receptor (AR), undetectable levels of p21WAF1 and prostate-specific antigen, and is resistant to apoptosis. The loss of prostate-specific antigen expression but not the p21WAF1 is attributable to gene silencing by hypermethylation. The high AR and undetectable p21WAF1 of AI cells, and lower AR but highly expressed p21WAF1 of androgen-dependent parental LNCaP cells, suggest a possibility of a functional link between these two proteins. Therefore, we examined the impact the modulation of AR will have on the expression of p21WAF1. Treatment of androgen-dependent cells with an androgen agonist, R1881, increased the AR protein level, whereas it simultaneously reduced the endogenous p21WAF1-protein 8-fold and the activity of a transiently transfected p21-promoter-reporter 10-fold. The down-regulation of p21WAF1 promoter appeared to be ARE mediated, dependent on AR, and not cell-type specific. Furthermore, a reduction of the AR level in AI cells by AR-antisense oligonucleotide increased the p21WAF1 promoter-reporter activity by approximately 4-fold, confirming a functional link between these two proteins. A strong, direct induction of p21WAF1 expression achieved by treatment of AI cells with trichostatin A produced a partial reversion of the AI phenotype evidenced by increased sensitivity of these cells to paclitaxel-induced apoptosis. Moreover, a reduction of AR level by antisense treatment, which also increased p21WAF1 expression, partially restored the androgen dependence of AI cells for growth. The functional link between AR dosage and p21WAF1 expression suggests that therapeutic reduction of AR protein in advanced prostate cancers with elevated AR levels may re-establish their hormone dependence and improve therapeutic response to repeated hormonal ablation and/or induction of apoptosis.
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PMID:Overexpressed androgen receptor linked to p21WAF1 silencing may be responsible for androgen independence and resistance to apoptosis of a prostate cancer cell line. 1160 92

We used rat prostate cancer cell stable transfectants that lacked either endogenous fibroblast growth factor (FGF)-1 secondary to constitutive expression of FGF-1 antisense RNA (aFa2-transfectants) or endogenous FGF-2 isoforms secondary to constitutive expression of FGF-2 antisense RNA (bFa9-transfectants) to examine the potential synergistic effects of mitogen and androgen as modulators of proliferation. During culture on 5% charcoal-stripped fetal bovine serum (CS-FBS), FGF-1 caused a 2- to 2.5-fold increase in the proliferation of aFa2-transfectants that lacked endogenous FGF-1 and retained full expression of FGF-2 isoforms. In marked constrast, bFa9-transfectants that lacked FGF-2 isoforms and retained full expression of FGF-1 died with exponential kinetics when cultured on either 5% CS-FBS or 5% FBS in the absence of FGF-2. However, FGF-2 promoted bFa9-transfectant survival and exponential proliferation during culture on either 5% CS-FBS or 5% FBS. The nonmetabolizable androgen R1881 did not affect proliferation of either the aFa2- transfectants, the bFa9-transfectants, or the parental prostate cancer cells used to generate these transfectants. Additionally, neither of the androgen receptor antagonists RU23908 or bicalutamide affected either FGF-1-mediated aFa2-transfectant proliferation or FGF-2-mediated bFa9-transfectant proliferation during culture on 5% CS-FBS. Notably, transient transfection analyses established R1881 concentration-dependent induction of chloramphenicol acetyltransferase activity in both aFa2-transfectants and bFa9-transfectants. Thus, the failure of either androgen or antiandrogen to affect either FGF-mediated or FGF-independent antisense-transfectant proliferation is not attributable to absence of functional androgen receptors. The results indicate that FGF effects in these androgen-resistant antisense transfectants do not involve either androgen-dependent or androgen-independent, mitogen-mediated androgen receptor activation. Our studies show that these rat prostate cancer cells are characterized by both retention of functional androgen receptors during development of androgen resistance and mitogen-mediated, autocrine or paracrine (or both) modulated proliferation. These are two prominent properties characteristic of advanced human prostate cancer.
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PMID:Neither fibroblast growth factor-1 nor fibroblast growth factor-2 is an androgen receptor coactivator in androgen-resistant prostate cancer. 1169 May 59


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