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)

Dietary isothiocyanates induce apoptosis in various cancer cell lines through a c-Jun N-terminal kinase (JNK)-dependent mechanism. We found that phenylethyl isothiocyanate (PEITC) was capable of inducing JNK activation and apoptosis in prostate cancer cell lines with distinct p53 statuses. PEITC induced JNK-mediated apoptotic signaling via a different pathway than that used by DNA-damaging agents, because genotoxicresistant LNCaP prostate cancer cells were equally sensitive to PEITC as parental LNCaP cells. PEITC did not induce significant MKK4 or MKK7 activation and did not activate JNK directly, suggesting that JNK and JNK upstream kinases are not primary targets of PEITC. The JNK dephosphorylation and inactivation rates were decreased in cells exposed to PEITC. Expression levels of M3/6, a JNK-specific phosphatase, were down-regulated by PEITC via a proteasome-dependent mechanism. Taken together, our data suggest that PEITC activates JNK through suppression of JNK dephosphorylation and that PEITC may be an alternative therapeutic agent for cancers that are resistant to genotoxic agents. This study also reveals that JNK phosphatases are potential targets for the development of novel cancer therapeutic agents.
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PMID:Phenylethyl isothiocyanate induces apoptotic signaling via suppressing phosphatase activity against c-Jun N-terminal kinase. 1217 15

Cancer cells frequently show high constitutive activity of the antiapoptotic transcription factor nuclear factor kappaB (NF-kappaB), which results in their enhanced survival. Activation of NF-kappaB classically depends on degradation of its inhibitor IkappaBalpha by the 26s proteasome. Specific proteasome inhibitors induce apoptosis in cancer cells and, at nonlethal concentrations, sensitize cells to the cytotoxic effects of ionizing radiation and chemotherapeutic drugs. Recently, the protease coded by the HIV-I virus has been shown to share cleavage activities with the proteasome. For this reason, we investigated whether the HIV-I protease inhibitor saquinavir can inhibit NF-kappaB activation, block 26s proteasome activity in prostate cancer cells, and promote their apoptosis. The effect of saquinavir on LPS/IFN-gamma-induced activation of NF-kappaB was assessed by gel-shift assays and by Western analysis of corresponding IkappaBalpha-levels. Its effect on 20s and 26s proteasome activity was analyzed with a fluorogenic peptide assay using whole cell lysates from LnCaP, DU-145, and PC-3 prostate cancer cells pretreated with saquinavir for 9 h. Proteasome inhibition in living cells was assessed using ECV 304 cells stably transfected with an expression plasmid for an ubiquitin/green fluorescence protein fusion protein (ECV 304/10). Apoptosis was monitored morphologically and by flow cytometry. Saquinavir treatment prevented LPS/IFN-gamma-induced activation of NF-kappaB in RAW cells and stabilized expression of IkappaBalpha. It inhibited 20s and 26s proteasome activity in lysates from LnCaP, DU-145, and PC-3 prostate cancer cells with an IC(50) of 10 micro M and caused the accumulation of an ubiquitin/green fluorescence protein fusion protein in living ECV 304/10 cells. Incubation of PC-3 and DU-145 prostate cancer, U373 glioblastoma, and K562 and Jurkat leukemia cells with saquinavir caused a concentration-dependent induction of apoptosis. In the case of PC-3 and DU-145, saquinavir sensitized the surviving cells to ionizing radiation. We conclude that saquinavir inhibits proteasome activity in mammalian cells as well as acting on the HIV-I protease. Because saquinavir induced apoptosis in human cancer cells, HIV-I protease inhibitors might become a new class of cytotoxic drugs, alone or in combination with radiation or chemotherapy.
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PMID:The human immunodeficiency virus (HIV)-1 protease inhibitor saquinavir inhibits proteasome function and causes apoptosis and radiosensitization in non-HIV-associated human cancer cells. 1223 89

Prostate cancer cells demonstrate slow growth kinetics and chemoresistance. Tea polyphenols have been shown to exert prostate cancer-preventative effects. Here we report that growth-arrested prostate cancer cells expressed high levels of a hyperphosphorylated Bcl-X(L) in mitochondria. Treatment with tea polyphenols or the major tea component epigallocatechin-3-gallate blocked expression of the hyper-, but not hypophosphorylated Bcl-X(L) in mitochondria, accompanied by cytochrome c release, caspase activation, and apoptosis. Studies using specific inhibitors suggest that tea inhibits p38 mitogen-activated protein kinase and the proteasome activities, leading to inhibition of Bcl-X(L) phosphorylation and induction of prostate cancer cell death.
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PMID:Inhibition of bcl-x(l) phosphorylation by tea polyphenols or epigallocatechin-3-gallate is associated with prostate cancer cell apoptosis. 1223 22

PS-341, a potent and selective proteasome inhibitor, is the prototype for a new class of therapeutics that targets the ubiquitin-proteasome pathway. It is active as a single agent and potentiates chemotherapy and radiation in pre-clinical models. Early phase clinical studies have demonstrated tolerability and activity in multiple myeloma, lymphoma, prostate cancer and lung cancer. By its mechanism of inhibiting protein degradation, PS-341 targets a wide-range of pathways that are relevant to tumor progression and therapy resistance, and can directly modulate expression of cyclins, p27(Kip1), p53, NF-kappaB, Bcl-2 and Bax. PS-341 is currently in phase I/II clinical development in lung cancer. This paper will review the pre-clinical and clinical experience with PS-341 as it relates to lung cancer.
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PMID:Integration of the proteasome inhibitor PS-341 (Velcade) into the therapeutic approach to lung cancer. 1286 67

PMEPA1 was originally identified as a highly androgen-induced gene by serial analysis of gene expression in androgen-treated LNCaP prostate cancer (CaP) cells. PMEPA1 expression is prostate abundant and restricted to prostatic epithelial cells. PMEPA1-encoded protein shows high sequence homology to a mouse N4wbp4-encoded protein that binds to Nedd4 protein, an E3 ubiquitin-protein ligase involved in ubiquitin-dependent, proteasome-mediated protein degradation. Studies from our and other laboratories have suggested the role of PMEPA1 in cell growth regulation as noted by androgen induction of PMEPA1 expression, elevated PMEPA1 expression in nontumorigenic revertants of tumor cell lines after chromosome 8p transfer, and PMEPA1 expression alterations (up- or down-regulation) in human tumors. Here, we demonstrate that PMEPA1 protein through its PY motifs interacts with WW domains of the human NEDD4 protein. Exogenous expression of PMEPA1, in widely used CaP cell lines DU145, PC3, LNCaP, and LNCaP sublines (C4, C4-2, and C4-2B), conferred cell growth inhibition, and at least one of the PY motifs of PMEPA1 may be involved in its cell growth inhibitory functions. Quantitative expression analysis of PMEPA1 in paired normal and tumor cells of 62 patients with primary CaP revealed tumor cells associated decreased expression in 40 of 62 patients that were significantly associated with higher pathologic stage and serum prostate-specific antigen. Taken together, PMEPA1 negatively regulates growth of androgen responsive or refractory CaP cells, and these functions may be mediated through the interaction of PMEPA1 with the NEDD4 protein involved in the ubiquitin-proteasome pathway. Loss or reduced PMEPA1 expression in CaP further suggests for its role in prostate tumorigenesis.
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PMID:PMEPA1, an androgen-regulated NEDD4-binding protein, exhibits cell growth inhibitory function and decreased expression during prostate cancer progression. 1290 94

Epidemiological studies have suggested that increased soy consumption is associated with reduced cancer occurrence. Genistein, a soy isoflavone, has been reported to inhibit the growth of human tumor cells although the involved molecular mechanisms are not clearly defined. Here we report that genistein inhibits the proteasomal chymotrypsin-like activity in vitro and in vivo. Computational docking studies suggest that the interaction of genistein with the proteasomal beta 5 subunit is responsible for inhibition of the chymotrypsin-like activity. Inhibition of the proteasome by genistein in prostate cancer LNCaP and breast cancer MCF-7 cells is associated with accumulation of ubiquitinated proteins and three known proteasome target proteins, the cyclin-dependent kinase inhibitor p27(Kip1), inhibitor of nuclear factor-kappa B (I kappa B-alpha), and the pro-apoptotic protein Bax. Genistein-mediated proteasome inhibition was accompanied by induction of apoptosis in these solid tumor cells. Finally, genistein induced proteasome inhibition and apoptosis selectively in simian virus 40-transformed human fibroblasts, but not in their parental normal counterpart. Our results suggest that the proteasome is a potential target of genistein in human tumor cells and that inhibition of the proteasome activity by genistein might contribute to its cancer-preventive properties.
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PMID:Inhibition of the proteasome activity, a novel mechanism associated with the tumor cell apoptosis-inducing ability of genistein. 1296 83

The proteome contains hundreds of proteins that in theory could be excellent therapeutic targets for the treatment of human diseases. However, many of these proteins are from functional classes that have never been validated as viable candidates for the development of small molecule inhibitors. Thus, to exploit fully the potential of the Human Genome Project to advance human medicine, there is a need to develop generic methods of inhibiting protein activity that do not rely on the target protein's function. We previously demonstrated that a normally stable protein, methionine aminopeptidase-2 or MetAP-2, could be artificially targeted to an Skp1-Cullin-F-box (SCF) ubiquitin ligase complex for ubiquitination and degradation through a chimeric bridging molecule or Protac (proteolysis targeting chimeric molecule). This Protac consisted of an SCF(beta-TRCP)-binding phosphopeptide derived from IkappaBalpha linked to ovalicin, which covalently binds MetAP-2. In this study, we employed this approach to target two different proteins, the estrogen (ER) and androgen (AR) receptors, which have been implicated in the progression of breast and prostate cancer, respectively. We show here that an estradiol-based Protac can enforce the ubiquitination and degradation of the alpha isoform of ER in vitro, and a dihydroxytestosterone-based Protac introduced into cells promotes the rapid disappearance of AR in a proteasome-dependent manner. Future improvements to this technology may yield a general approach to treat a number of human diseases, including cancer.
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PMID:Development of Protacs to target cancer-promoting proteins for ubiquitination and degradation. 1452 58

Bortezomib (Velcade, PS-341) is a dipeptide boronate inhibitor of the 26S proteasome developed for use in cancer therapy. Here we examined the effects of bortezomib on apoptosis and angiogenesis in derivatives of two popular human prostate cancer cell lines (LNCaP-Pro5 and PC3M-Pro4). Bortezomib strongly inhibited proliferation in both cell lines in vitro, but the PC3M-Pro4 cells were significantly more sensitive than the LNCaP-Pro5 cells to bortezomib-induced apoptosis. The compound also significantly inhibited the growth of LNCaP-Pro5 and LNCaP-Pro4 tumor xenografts, but the mechanisms involved in tumor growth inhibition differed in the two models. Bortezomib-treated LNCaP-Pro5 tumors displayed reduced microvessel densities and vascular endothelial cell growth factor secretion and high levels of endothelial cell apoptosis consistent with angiogenesis inhibition. In contrast, PC3M-Pro4 tumors were poorly vascularized at baseline, and bortezomib failed to induce significant changes in microvessel density, angiogenic factor secretion, or endothelial cell death in this model. Rather, growth inhibition in the PC3M-Pro4 tumors was associated with direct increases in tumor cell death. Together, our results confirm that bortezomib is active in preclinical models of human prostate cancer, but its effects on apoptosis versus angiogenesis are cell type dependent.
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PMID:Differential effects of the proteasome inhibitor bortezomib on apoptosis and angiogenesis in human prostate tumor xenografts. 1455 2

Advanced prostate cancer is resistant to current therapeutic strategies. Bortezomib (Velcade; previously called PS-341) is a potent and specific inhibitor of the 26S proteasome that is currently in clinical trials for treatment of various malignancies, including prostate cancer. We investigated the effects of bortezomib on p53 in the LNCaP-Pro5 prostate cancer cell line. Bortezomib induced strong stabilization of p53, but it did not promote phosphorylation on serines 15 and 20, and p53 remained bound to its inhibitor, mdm2. Nonetheless, bortezomib stimulated p53 translocation to the nucleus (not mitochondria) and enhanced p53 DNA binding, accumulation of p53-dependent transcripts, and activation of a p53-responsive reporter gene. Furthermore, stable LNCaP-Pro5 transfectants of LNCaP-Pro5 expressing the p53 inhibitor human papillomavirus-E6 displayed reduced bortezomib-induced p53 activation and cell death. Together, our data demonstrate that bortezomib stimulates p53 activation via a novel mechanism.
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PMID:The proteasome inhibitor bortezomib stabilizes a novel active form of p53 in human LNCaP-Pro5 prostate cancer cells. 1461 32

Animal studies have demonstrated that a dietary polyphenol known as tannic acid (TA) exhibits anticarcinogenic activity in chemically induced cancers. Most recently, we have reported that TA and ester-bond containing green tea polyphenols are potent proteasome inhibitors in vitro and in vivo. We hypothesize that CellQuest, a patented formula which contains high level of TA obtained from a musaceas (plantain) plant extract, will inhibit the tumor cell proteasome activity. Here, we report that a partially purified CellQuest fraction, S3, potently inhibits the proteasomal chymotrypsin-like activity of Jurkat T cell extracts in a concentration-dependent manner. Inhibition of the proteasome by S3 in leukemia Jurkat T, simian virus 40-transformed and prostate cancer LNCaP cells results in accumulation of ubiquitinated proteins and the natural proteasome substrate p27Kip1, followed by induction of apoptosis. In contrast, non-transformed, immortalized human natural killer cells and normal human fibroblasts are resistant to S3-mediated proteasome inhibition and apoptosis induction. Our present study suggests that CellQuest targets and inhibits the proteasome selectively in tumor cells, which may contribute to the claimed anticancer activity.
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PMID:A natural musaceas plant extract inhibits proteasome activity and induces apoptosis selectively in human tumor and transformed, but not normal and non-transformed, cells. 1461 61


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