Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.25.1 (proteasome)
28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Primary effusion lymphomas (PELs) are a rare type of non-Hodgkin's lymphoma that are resistant to cytotoxic chemotherapy. PELs manifest constitutive activation of nuclear factor kappa B (NF-kappaB), and inhibition of NF-kappaB induces apoptosis of PELs and sensitizes to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced death. Bortezomib (PS-341), a peptidyl boronic acid inhibitor of the proteasome, is a potent agent against a wide range of hematologic malignancies and has been shown to inhibit NF-kappaB. Thus, we examined the cytotoxic effects of bortezomib alone and in combination with various drugs. Bortezomib potently inhibited NF-kappaB in PEL cells in a dose-dependent manner. In addition, bortezomib inhibited growth and induced apoptosis of PEL cell lines (IC(50) values of 3.4-5.0 nM). Results of drug interactions between bortezomib and chemotherapy (doxorubicin and Taxol) were schedule-dependent: synergistic interactions were generally observed when PEL cells were pretreated with bortezomib prior to chemotherapy, whereas additive or even antagonistic interactions occurred with chemotherapy pretreatment or simultaneous treatment with bortezomib and chemotherapy. Most schedules of bortezomib and dexamethasone were synergistic, although pretreatment with dexamethasone resulted in additive interactions. Effects of combinations of bortezomib and TRAIL were generally additive. Thus, bortezomib represents a promising potential therapy for the treatment of PEL.
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PMID:Antitumor effects of bortezomib (PS-341) on primary effusion lymphomas. 1534 45

Proteasome inhibition is a novel, targeted approach in cancer therapy. Both natural and synthetic proteasome inhibitors selectively penetrate cancer cells, disrupting the orderly destruction of key regulatory proteins involved in tumorigenesis and metastasis. Disrupting the orderly destruction of regulatory proteins causes an imbalance of these proteins within the cell, which interferes with the systematic activation of signaling pathways required to maintain tumor cell growth and survival; therefore, cellular replication is inhibited and apoptosis ensues. Bortezomib (PS-341, Velcade), the first proteasome inhibitor evaluated in human clinical trials, has been approved by the US Food and Drug Administration for use in patients with refractory or relapsed multiple myeloma. Preclinical study results show that bortezomib suppresses tumor cell growth, induces apoptosis, overcomes resistance to standard chemotherapy agents and radiation therapy, and inhibits angiogenesis. Phase I study results established the antitumor activity of bortezomib, administered alone or in combination with standard chemotherapy agents, in patients with advanced hematologic malignancies or solid tumors, usually without additive toxicities. The results of phase II studies further supported the antitumor activity of bortezomib in patients with refractory or relapsed multiple myeloma and non-Hodgkin's lymphoma; less impressive results were observed in patients with stage IV renal cell cancer. Studies evaluating bortezomib in earlier stages of multiple myeloma, including first-line therapy, are under way. Evidence suggests that certain prognostic factors, such as older age and bone marrow containing more than 50% plasma cells, may be useful in predicting response and survival time in multiple myeloma patients receiving bortezomib. Further studies of bortezomib are needed to establish its full spectrum of activity, the ideal regimens for various tumor types, and clinically useful prognostic indicators that predict successful outcomes.
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PMID:Discovery, Development, and clinical applications of bortezomib. 1568 97

Bortezomib (PS-341, Velcade) is a novel, first-in-class proteasome inhibitor with antitumor activity against a number of hematologic and nonhematologic malignancies. Based on the results of phase II clinical trials, bortezomib received accelerated US Food and Drug Administration approval on May 13, 2003, for the treatment of multiple myeloma patients whose disease has progressed after they have received at least two prior conventional therapies. The results of phase III studies evaluating bortezomib as first- or second-line therapy, or in combination with other commonly prescribed therapies in multiple myeloma patients, are eagerly awaited. Studies assessing the antitumor effects of bortezomib in other hematologic malignancies and solid tumors are also under way. A thorough understanding of the pharmacology, pharmacodynamics, and pharmacokinetics of this novel compound is essential for appropriate prescribing and monitoring of bortezomib therapy. Bortezomib is rapidly distributed into tissues after administration of a single dose, with an initial plasma distribution half-life of less than 10 minutes, followed by a terminal elimination half-life of more than 40 hours. Maximum proteasome inhibition occurs within 1 hour and recovers close to baseline within 72 to 96 hours after administration. Bortezomib is primarily metabolized by oxidative deboronation to one of two inactive enantiomers that are further processed and eliminated, both renally and in bile. Bortezomib has been shown to be a substrate of several cytochrome P450 isoenzymes using in vitro systems. Adverse effects of bortezomib are generally mild and effectively managed with supportive care. Bortezomib should be administered with caution to patients with preexisting fluid retention and patients with baseline platelet counts of less than 70,000/microL. Dose reductions are recommended for patients experiencing peripheral neuropathy, grade 3 or higher nonhematologic toxicities, or grade 4 hematologic toxicities. Formal drug interaction studies have not been performed, but bortezomib has been administered in combination with a variety of antitumor agents without significant alterations to its pharmacokinetic or pharmacodynamic profile.
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PMID:Pharmacology, pharmacokinetics, and practical applications of bortezomib. 1568 98

Inhibitors of the proteasome have long been used in studies of protein turnover, but in a notable example of successful translational research they have made the leap from the laboratory into the clinical arena. The proteasome inhibitor bortezomib (VELCADE, formerly known as PS-341), has recently been approved in the United States for treatment of patients with multiple myeloma who have received at least two prior therapies, and have demonstrated disease progression on their last therapy. Furthermore, studies of this agent in other hematologic malignancies and solid tumors are underway, and other proteasome inhibitors for clinical use are under development as well. This chapter provides the reader with guidelines for the optimal clinical administration of VELCADE for its currently approved indication, as well as some suggestions for subsequent management of treatment-related events in these patients.
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PMID:Proteasome inhibitors in cancer therapy. 1591 44

Bortezomib is a highly selective, reversible inhibitor of the 26S proteasome that is indicated for single-agent use in the treatment of patients with multiple myeloma who have received at least 2 prior therapies and are progressing on their most recent therapy. Clinical investigations have been completed or are under way to evaluate the safety and efficacy of bortezomib alone or in combination with chemotherapy in multiple myeloma, both at relapse and presentation, as well as in other cancer types. The antiproliferative, proapoptotic, antiangiogenic, and antitumor activities of bortezomib result from proteasome inhibition and depend on the altered degradation of a host of regulatory proteins. Exposure to bortezomib has been shown to stabilize p21, p27, and p53, as well as the proapoptotic Bid and Bax proteins, caveolin-1, and inhibitor kappaB-alpha, which prevents activation of nuclear factor kappaB-induced cell survival pathways. Bortezomib also promoted the activation of the proapoptotic c-Jun-NH2 terminal kinase, as well as the endoplasmic reticulum stress response. The anticancer effects of bortezomib as a single agent have been demonstrated in xenograft models of multiple myeloma, adult T-cell leukemia, lung, breast, prostate, pancreatic, head and neck, and colon cancer, and in melanoma. In these preclinical in vivo studies, bortezomib treatment resulted in decreased tumor growth, angiogenesis, and metastasis, as well as increased survival and tumor apoptosis. In several in vitro and/or in vivo cancer models, bortezomib has also been shown to enhance the antitumor properties of several antineoplastic treatments. Importantly, bortezomib was generally well tolerated and did not appear to produce additive toxicities when combined with other therapies in the dosing regimens used in these preclinical in vivo investigations. These findings provide a rationale for further clinical trials using bortezomib alone or in combination regimens with chemotherapy, radiation therapy, immunotherapy, or novel agents in patients with hematologic malignancies or solid tumors.
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PMID:Preclinical evaluation of the proteasome inhibitor bortezomib in cancer therapy. 1592 91

The ubiquitin-proteasome pathway is a principal intracellular mechanism for controlled protein degradation and has recently emerged as an attractive target for anticancer therapies since several cell cycle regulators and modulators of apoptosis are degraded through this pathway. The current state of the field of proteasome inhibitors and their prototypic member, bortezomib, which was recently approved by the US Food and Drug Administration for the treatment of advanced multiple myeloma, is reviewed. Particular emphasis is placed on the preclinical research data that became the basis for eventual clinical applications of proteasome inhibitors, an overview of the clinical development of this exciting drug class in multiple myeloma, and an appraisal of possible uses in other hematologic malignancies, such as non-Hodgkin's lymphomas.
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PMID:Proteasome inhibition as a therapeutic strategy for hematologic malignancies. 1600 54

The proteasome is responsible for the degradation of intracellular proteins, including several involved in cell cycle control and the regulation of apoptosis. Preclinical studies have shown that the proteasome inhibitor bortezomib decreases proliferation, induces apoptosis, enhances the activity of chemotherapy and radiation, and reverses chemoresistance in a variety of hematologic and solid malignancy models in vitro and in vivo. Proteasome inhibition with bortezomib has specifically promoted apoptosis of tumor cells through the stabilization of p53, p21, p27, Bax, and IkappaBalpha, resulting in nuclear factor kappaB inhibition. Bortezomib was the first proteasome inhibitor to enter clinical trials. In two Phase II trials, SUMMIT and CREST, it was found that treatment with bortezomib, alone or in combination with dexamethasone, produced durable responses with meaningful survival benefits in patients with recurrent and/or refractory multiple myeloma. In the APEX Phase III trial, bortezomib produced significant survival benefits and improved response rates over high-dose dexamethasone at first recurrence and beyond in patients with multiple myeloma. Clinical trials evaluating the safety and activity of bortezomib alone or in combination regimens with dexamethasone, doxorubicin, melphalan, prednisone, and/or thalidomide in the treatment of patients with newly diagnosed multiple myeloma have shown encouraging results. Preliminary studies suggest that bortezomib may serve as induction therapy before stem cell transplantation. Proteasome inhibition with bortezomib also has shown activity with manageable toxicity in mantle cell and other lymphomas, leukemias, and solid malignancies, including nonsmall cell lung carcinoma. Further studies with bortezomib as monotherapy and in combination regimens in the treatment of solid and hematologic malignancies are warranted.
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PMID:Proteasome inhibition and its clinical prospects in the treatment of hematologic and solid malignancies. 1617 3

Since last years, the proteasome has emerged as a real and exciting target for anticancer therapy. Velcade (bortezomib, formerly known as PS341) remains the first selective proteasome inhibitor that has demonstrated significant preclinical activity in several tumor models and a significant efficacy in patients with refractory or relapsed multiple myeloma, resulting in an accelerated approval in US and Europe in such a setting. The major biological effect of bortezomib is the inhibition of the nuclear transcription factor NFkappaB, with subsequent inhibition of the growth tumor cells, induction of apoptosis, inhibition of angiogenesis and of cellular adhesion. The better understanding of the role of proteasome in the regulation of tumor cell growth has led to the development of new therapeutic approaches, notably in patients with multiple myeloma but also seems to hold interesting promises in other hematologic malignancies and solid tumors. This review provides a summary of the rationale for using proteasome inhibitors and an update on available and ongoing clinical studies involving human malignancies.
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PMID:Proteasome inhibition: a new approach for the treatment of malignancies. 1631 23

Recent advanced developments in our understanding of cancer cell biology have begun to generate a host of new targets that are proving to be valuable substrates for new drug development. One example includes our ever-increasing understanding of the complex biology surrounding the ubiquitin-proteasome pathway. For years there have been a variety of compounds used in the laboratory that have been shown to inhibit the proteasome, though many of these compounds have proven to be relative non-specific inhibitors of intracellular and proteasome proteases. The recent synthesis of 1 novel inhibitor, bortezomib (formerly known as PS341), has proven to be an effective reversible inhibitor of the chymotryptic protease in the 26S proteasome. Proteasome inhibition represents a new approach for the treatment of many forms of cancer, especially select hematologic malignancies. Bortezomib has been approved by the United States Food and Drug Administration for the treatment of relapsed or refractory multiple myeloma. In addition to myeloma, bortezomib has also shown promising activity in the treatment of select types of non-Hodgkin's lymphomas (NHLs). Several single-agent phase II clinical trials in patients with a host of different NHL histologies have demonstrated that bortezomib has reproducible activity in mantle-cell lymphoma (MCL) and follicular lymphoma (FL), with some suggestion of activity in marginal zone lymphoma. The promising activity in these smaller studies has led to a number of larger multicenter studies with bortezomib in combination with rituximab in MCL, FL, and marginal zone lymphoma. The collective early experience from these studies continues to support the activity of bortezomib in these histologies of NHL. Herein, some of the biologic rationale for using proteasome inhibitors in lymphoma as well as some of the clinical data from these promising studies are discussed.
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PMID:Marked clinical activity of the proteasome inhibitor bortezomib in patients with follicular and mantle-cell lymphoma. 1635 24

The ubiquitin-proteasome pathway (UPP) is the major eukaryotic mechanism for regulated intracellular proteolysis. Targeting this pathway with proteasome inhibitors has been validated as a rational strategy against hematologic malignancies, but for most solid tumor populations, including breast cancer, such agents have not shown encouraging activity. However, there is an increasing body of evidence showing that UPP dysregulation plays an important role in mammary tumorigenesis. Moreover, modulation of ubiquitin-proteasome function is emerging as a rational strategy to enhance chemosensitivity and overcome chemoresistance. Taken together, these facts suggest that we are only beginning to appreciate the relevance of this pathway for the current and future therapy of patients with breast cancer. This review provides an overview of the biology of the UPP, its role in the malignant process, the current state of knowledge regarding clinical heat shock protein and proteasome inhibition, and some likely future directions that may enhance our ability to exploit this pathway therapeutically.
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PMID:Targeting the ubiquitin-proteasome pathway in breast cancer therapy. 1655 79


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