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)

Previously, we showed that the proteasome inhibitor bortezomib/Velcade (formerly PS-341) synergizes with the protein tumor necrosis factor alpha-related apoptosis-inducing ligand (TRAIL), a ligand for certain death receptors, to induce apoptosis in cell lines derived from prostate and colon cancers. Because apoptosis is often triggered by BH3-only proteins of the Bcl-2 family, we have explored the hypothesis that bortezomib contributes to the apoptosis by up-regulating their levels. Indeed, bortezomib induced increases of Bik and/or Bim in multiple cell lines but not notably of two other BH3-only proteins (Puma and Bid) nor other family members (Bax, Bak, Bcl-2, and Bcl-xL). The increase in Bik levels seems to reflect inhibition by bortezomib of its proteasome-mediated degradation. Importantly, both Bik and Bim seem central to the proapoptotic function of bortezomib, because mouse embryo fibroblasts in which the genes for both Bik and Bim had been disrupted were refractory to its cytotoxic action. Similarly, the synergy between bortezomib and TRAIL in killing human prostate cancer cells was impaired in cells in which both Bik and Bim were down-regulated by RNA interference. Further evidence that bortezomib acts through the mitochondrial pathway regulated by the Bcl-2 family is that deficiency for APAF-1, which acts downstream of Bcl-2, also blocked its apoptotic effect. These results implicate BH3-only proteins, in particular both Bik and Bim, as important mediators of the antitumor action of bortezomib and establish their role in its enhancement of TRAIL-induced apoptosis.
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PMID:The proteasome inhibitor bortezomib sensitizes cells to killing by death receptor ligand TRAIL via BH3-only proteins Bik and Bim. 1576 53

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor family of cytokines that induces apoptosis in some tumor cells but not in normal cells. Unfortunately, many human cancer cell lines are refractory to TRAIL-induced cell death, and the molecular mechanisms underlying resistance are unclear. Here we report that TRAIL resistance was reversed in human bladder and prostate cancer cell lines by the proteasome inhibitor bortezomib (PS-341, Velcade). Synergistic induction of apoptosis occurred within 4 to 6 hours in cells treated with TRAIL plus bortezomib and was associated with accumulation of p21(WAF-1/Cip-1) (p21) and inhibition of cyclin-dependent kinase (cdk) activity. Roscovitine, a specific cdk1/2 inhibitor, also sensitized cells to TRAIL. Silencing p21 expression reduced levels of DNA fragmentation by 50% in cells treated with bortezomib and TRAIL, confirming that p21 was required for the response. Analysis of the TRAIL pathway revealed that caspase-8 processing was enhanced in a p21-dependent fashion in cells exposed to TRAIL and bortezomib as compared with cells treated with TRAIL alone. Thus, all downstream components of the pathway (Bid cleavage, cytochrome c release, and caspase-3 activation) were amplified. These data strongly suggest that p21-mediated cdk inhibition promotes TRAIL sensitivity via caspase-8 activation and that TRAIL and bortezomib should be combined in appropriate in vivo models as a possible approach to solid tumor therapy.
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PMID:Bortezomib abolishes tumor necrosis factor-related apoptosis-inducing ligand resistance via a p21-dependent mechanism in human bladder and prostate cancer cells. 1593 Mar 12

Recent research suggests that copper could be used as a novel selective target for cancer therapies. Copper is a co-factor essential for tumor angiogenesis processes and high levels of copper have been found in many types of human cancers, including prostate, breast and brain. We have reported that organic copper-containing compounds, such as 8-hydroxyquinoline-copper(II), are a novel class of proteasome inhibitors and tumor cell apoptosis inducers (Daniel et al., Biochem Pharmacol. 2004;67:1139-51). Most recently, we have found that when complexed with copper, the known antioxidant pyrrolidine dithiocarbamate (PDTC) forms a potent proteasome inhibitor in human breast cancer, but not normal cells (Daniel, Chen, et al., submitted). In the current study, we investigate whether the PDTC-copper complex can play similar roles in inhibiting the proteasomal activity and consequently inducing apoptosis in human prostate cancer cells. We used tetrathiomolybdate (TM), a strong copper chelator currently being tested in clinical trials, as a control. We report here that after binding to copper, PDTC, but not TM, can inhibit the proteasomal chymotrypsin-like activity, suppress proliferation, induce apoptotic cell death, and inhibit uptake of radiopharmaceutical 2-[18F]Fluoro-2-deoxy-D-glucose in cultured human prostate cancer cells. In contrast, PDTC, TM or copper alone or a TM-copper mixture had no such effects. Our study suggests that high copper levels in human prostate cancer in vivo can be targeted by a ligand such as PDTC, resulting in formation of an active proteasome inhibitor and apoptosis inducer specifically in prostate tumor, but not normal cells.
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PMID:Inhibition of prostate cancer cellular proteasome activity by a pyrrolidine dithiocarbamate-copper complex is associated with suppression of proliferation and induction of apoptosis. 1597 May 47

Combined treatment with a proteasome inhibitor and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising strategy for cancer therapy. Proteasome inhibitors induce the expression of death receptor 5 (DR5), a receptor for TRAIL, and sensitize cancer cells to TRAIL-induced apoptosis; however, the molecular mechanism of DR5 up-regulation has not been elucidated. In this study, we report that CCAAT/enhancer-binding protein homologous protein (CHOP) is a regulator of DR5 induction by proteasome inhibitor MG132. MG132 induced DR5 expression at a protein and mRNA level in prostate cancer DU145 cells. Furthermore, MG132 increased DR5 promoter activity. Using a series of deletion mutant plasmids containing DR5 promoters of various sizes, we found that MG132 stimulated the promoter activity via the region of -289 to -253. This region contained a CHOP-binding site. Site-directed mutation of the site abrogated the promoter activity enhanced by MG132. An electrophoretic mobility shift assay showed that CHOP directly bound to the MG132-responsive site on the DR5 promoter. Expression of the CHOP protein was increased with MG132 along with DR5 up-regulation. Furthermore, CHOP small interfering RNA attenuated the DR5 up-regulation due to MG132. These results indicate that the proteasome inhibitor MG132 induces DR5 expression through CHOP up-regulation.
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PMID:Proteasome inhibitor MG132 induces death receptor 5 through CCAAT/enhancer-binding protein homologous protein. 1599 39

Overexpression of the helix-loop-helix protein Id-1 has been reported in over 20 types of cancer. While a number of factors have been demonstrated to regulate Id-1 gene transcription, little is known about the mechanisms responsible for its degradation. In this study, we have demonstrated that Id-1 protein stability was regulated by TNFalpha in prostate cancer cells. We found that exposure of prostate cancer cell lines, DU145 and PC-3, to TNFalpha resulted in a rapid and significant downregulation of the Id-1 protein level. The fact that neither the Id-1 promoter activity nor the Id-1 mRNA level was affected by the TNFalpha treatment suggested that the decrease in Id-1 protein was not due to the suppression of gene transcription. In addition, the half-life of the Id-1 protein was decreased in both cell lines in the presence of TNFalpha, and the addition of an ubiquitin/proteasome inhibitor (MG-132) prior to the TNFalpha treatment completely blocked the effect of the TNFalpha-induced Id-1 protein degradation. Furthermore, introduction of a Flag-tag sequence into the N-terminus region of the Id-1 protein, which has been shown to stabilize the protein, was able to protect the Id-1 protein from TNFalpha-induced degradation. These results suggest that TNFalpha downregulated Id-1 through activation of the ubiquitin/proteasome degradation pathway in prostate cancer cells. Interestingly, in both DU145 and PC-3 cells, the decrease of Id-1 protein was associated with the activation of apoptotic pathway, as evidenced by the increased expression of cleaved PARP and caspase 3. In addition, TNFalpha failed to downregulate Id-1 in a sub-line of LNCaP cells that was resistant to TNFalpha-induced apoptosis. These results further suggest that the downregulation of Id-1 may facilitate TNFalpha-induced apoptosis in prostate cancer cells. In conclusion, our findings indicate that Id-1 protein may be regulated by TNFalpha through the ubiquitin/proteasome degradation pathway and the stability of the Id-1 protein appears to correlate with the sensitivity of TNFalpha-induced apoptosis.
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PMID:Proteasome mediated degradation of Id-1 is associated with TNFalpha-induced apoptosis in prostate cancer cells. 1612 20

Prostate adenocarcinoma is the most common malignancy diagnosed in males, and bone metastases remain a significant source of morbidity and mortality in this population. The ubiquitin-proteasome cascade is responsible for the degradation of intracellular proteins, and this pathway is thought to play an essential role in the development of malignancies by altering the levels of various proteins involved in the regulation of cell division. Proteasome inhibitors represent a class of chemotherapeutic agents that have been shown to inhibit tumor growth by a number of different mechanisms. Using a murine intratibial injection model, we examined the effects of the proteasome inhibitor bortezomib on the establishment and progression of osteolytic bone lesions induced by human CaP cells (PC-3 cell line). In this study, the intravenous administration of bortezomib (1 mg/kg) did not prevent the initial formation of osteolytic lesions but did appear to inhibit their growth in a time-dependent fashion. In contrast, bortezomib therapy effectively inhibited the establishment and progression of subcutaneous PC-3 tumors, which served as a positive control. These results suggest that proteasome inhibitors such as bortezomib may represent a novel adjunctive therapy for the treatment of osteolytic skeletal metastases, especially when treatment is initiated early during the disease process.
Prostate Cancer Prostatic Dis 2005
PMID:Effects of the proteasome inhibitor bortezomib on osteolytic human prostate cancer cell metastases. 1613 17

The proteasome inhibitor Velcade (bortezomib/PS-341) has been shown to block the targeted proteolytic degradation of short-lived proteins that are involved in cell maintenance, growth, division, and death, advocating the use of proteasomal inhibitors as therapeutic agents. Although many studies focused on the use of one proteasomal inhibitor for therapy, we hypothesized that the combination of proteasome inhibitors Lactacystin (AG Scientific, Inc., San Diego CA) and MG132 (Biomol International, Plymouth Meeting, PA) may be more effective in inducing apoptosis. Additionally, this regimen would enable the use of sublethal doses of individual drugs, thus reducing adverse effects. Results indicate a significant increase in apoptosis when LNCaP prostate cancer cells were treated with increasing levels of Lactacystin, MG132, or a combination of sublethal doses of these two inhibitors. Furthermore, induction in apoptosis coincided with a significant loss of IKKalpha, IKKbeta, and IKKgamma proteins and NFkappaB activity. In addition to describing effective therapeutic agents, we provide a model system to facilitate the investigation of the mechanism of action of these drugs and their effects on the IKK-NFkappaB axis.
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PMID:Combination of proteasomal inhibitors lactacystin and MG132 induced synergistic apoptosis in prostate cancer cells. 1635 93

The proteasome-mediated protein degradation is critical for regulation of a variety of cellular processes, including cell cycle, cell death, differentiation and immune response. Proteasome inhibitors have recently been shown to be potent anti-cancer agents against a variety of cancer cells. Our study demonstrated that proteasome inhibitor MG132 (carbobenzoxy-L-leucyle-L-leucyl-L-leucinal) was a potent death-inducing agent for PC3 prostate cancer cells. MG132-induced cell death was partially inhibited by pan-caspase inhibitor zAVD-fmk and translational inhibitor cycloheximide. To understand the signaling pathways of proteasome inhibitor-induced cell death, we performed gene profiling study using Affymetrix human DNA microarrays to identify the genes whose expression was affected by proteasome inhibitor MG132 in PC3 cells. The genes with more than threefold increased expression induced by MG132 were functionally categorized into the following groups: heat shock and chaperone proteins, ubiquitination and protein degradation, transcription/translation factors, cell death and cell cycle arrest, signaling molecules and enzymes, and secreted cytokines. Among them, heat shock proteins and anti-oxidant enzymes may promote cell survival, while pro-death proteins such as GADD45B and STK17a may promote cell death. Interestingly, expression of a few autophagic genes was elevated by MG132 treatment. Furthermore, autophagy inhibitor 3-methyladenine partially inhibited MG132-induced cell death, indicating that autophagic cell death may contribute to MG132-induced cell death. Taken together, our results demonstrated that proteasome inhibition elicits activation of multiple signaling pathways in prostate cancer cells.
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PMID:Proteasome inhibition induces both pro- and anti-cell death pathways in prostate cancer cells. 1641 76

Histone deacetylase inhibitors (HDACI) are potential therapeutic agents that inhibit tumor cell growth and survival. Although there are several publications regarding the effects of HDACIs on prostate cancer cell growth, their mechanism(s) of action remains undefined. We treated several human prostate cancer cell lines with the HDACI trichostatin A and found that trichostatin A induced cell death in androgen receptor (AR)-positive cell lines to higher extent compared with AR-negative cell lines. We then discovered that trichostatin A and other HDACIs suppressed AR gene expression in prostate cancer cell lines as well as in AR-positive breast carcinoma cells and in mouse prostate. Trichostatin A also induced caspase activation, but trichostatin A-induced AR suppression and cell death were caspase independent. In addition, we found that doxorubicin inhibited AR expression, and p21 protein completely disappeared after simultaneous treatment with trichostatin A and doxorubicin. This effect may be attributed to the induction of protease activity under simultaneous treatment with these two agents. Further, simultaneous treatment with trichostatin A and doxorubicin increased cell death in AR-positive cells even after culturing in steroid-free conditions. The protease/proteasome inhibitor MG132 protected AR and p21 from the effects of trichostatin A and doxorubicin and inhibited trichostatin A-induced cell death in AR-positive prostate cells. Taken together, our data suggest that the main mechanism of trichostatin A-induced cell death in AR-positive prostate cancer is inhibition of AR gene expression. The synergistic effect of simultaneous treatment with trichostatin A and doxorubicin is mediated via inhibition of AR expression, induction of protease activity, increased expression of p53, and proteolysis of p21.
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PMID:Mechanisms of cell death induced by histone deacetylase inhibitors in androgen receptor-positive prostate cancer cells. 1651 42

The purpose of this study is to evaluate the utility of MG-132, a broad spectrum proteasome inhibitor, to selectively enhance radiation sensitivity in prostate cancer without affecting normal surrounding urothelial tissue. PC3 prostate cancer cells and normal URO-tsa bladder epithelial cells were treated with or without MG-132 and exposed to 0, 2, 4, or 6 Gy radiation. Cell viability and clonogenic survival assays were performed, and nuclear factor kappa-B (NF-kappaB) activity was evaluated with electrophoretic mobility shift assay (EMSA). MG-132 was associated with decreased cell viability (between 24% and 33%) and clonogenic survival (between 71% and 88%) alone and in combination with radiation in PC3 cells. MG-132 had no effect on cell viability or clonogenic survival following radiation in URO-tsa cells. Constitutive and radiation-induced NF-kappaB binding activity was higher in PC3 cells compared with URO-tsa cells. Furthermore, MG-132 at concentrations associated with reductions in cell viability and clongenic survival inhibited NF-kappaB binding activity in PC3 cells with no effect in URO-tsa cells. These results provide strong evidence that proteasome inhibition and concomitant NF-kappaB inhibition can be used to selectively enhance tumor radiation sensitivity in prostate cancer without affecting normal surrounding bladder tissue.
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PMID:Selectively enhanced radiation sensitivity in prostate cancer cells associated with proteasome inhibition. 1659 99


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