Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0026764 (multiple myeloma)
 36,148 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ubiquitin-proteasome pathway is a well-characterized mechanism deputed to the degradation of intracellular proteins. Proteasomal degradation intervenes in the regulation of numerous cellular functions including signal transduction, apoptosis, cell cycle, and antigen presentation. In vitro and in vivo studies have shown that both normal and malignant cells of the immune system are exquisitely affected by inhibition of proteasome activity. This property is currently exploited in the treatment of multiple myeloma and mantle cell lymphoma, two B-cell malignancies that respond to treatment with the proteasome inhibitor bortezomib. Pharmacological inhibitors of the proteasome also affect function and survival of B and T lymphocytes and of dendritic cells and were shown to reduce autoimmune and inflammatory manifestations in several models of immune-mediated disorders. The present review offers an overview of the mechanisms implicated in the immunomodulatory effects of proteasome inhibitors and discusses prospective future applications for these small molecules in immune and inflammatory diseases.
 ...
PMID:The proteasome and its inhibitors in immune regulation and immune disorders. 1734 Nov 90

c-Myc is a highly unstable transcription factor whose deregulation and increased expression are associated with cancer. Degrasyn, a small synthetic molecule, induces rapid degradation of c-Myc protein in MM-1 multiple myeloma and other tumor cell lines. Destruction of c-Myc by degrasyn requires the presence of a region of c-Myc between amino acid residues 316 and 378 that has not previously been associated with c-Myc stability. Degrasyn-induced degradation of c-Myc depends on proteasomes but is independent of the degron regions previously shown to be important for ubiquitin-mediated targeting and proteasomal destruction of the protein. Degrasyn-dependent c-Myc proteolysis is not mediated by any previously identified c-Myc regulatory mechanism, does not require new protein synthesis, and does not depend on the nuclear localization of c-Myc. Degrasyn reduced c-Myc levels in A375 melanoma cells and in A375 tumors in nude mice, and this activity correlated with tumor growth inhibition. Together, these results suggest that degrasyn reduces the stability of c-Myc in vitro and in vivo through a unique signaling process that uses c-Myc domains not previously associated with c-Myc regulation.
 ...
PMID:Degrasyn activates proteasomal-dependent degradation of c-Myc. 1744 Jan 6

Cyclin D2 plays an important role in regulation of hematopoietic cell proliferation by cytokines and is implicated in oncogenesis of various hematopoietic malignancies. However, mechanisms regulating cyclin D2 stability and its expression level have remained to be known. Here, we demonstrate that interleukin-3 signaling stabilizes cyclin D2 by inhibition of glycogen synthase kinase-3beta (GSK3beta) through Janus kinase2-dependent activation of phosphatidylinositol 3'-kinase (PI3K)/Akt signaling pathway in hematopoietic 32Dcl3 cells. On the other hand, osmotic stress was shown to induce a rapid proteasomal degradation of cyclin D2, which was mediated by activation of p38. GSK3beta and p38 was demonstrated to phosphorylate cyclin D2 on Thr280 in vitro, while a cyclin D2 mutant with this residue substituted with Ala was found to be resistant to ubiquitination and proteasome-dependent degradation in 32Dcl3 cells. Inhibition of the PI3K pathway or induction of osmotic stress also caused a rapid proteasomal degradation of cyclin D2 in primary leukemic or myeloma cells. These results indicate that cyclin D2 expression in normal and malignant hematopoietic cells is regulated by ubiquitin/proteasome-dependent degradation that is triggered by Thr280 phosphorylation by GSK3beta or p38, which is induced by inhibition of the PI3K pathway or by osmotic stress, respectively.
 ...
PMID:Glycogen synthase kinase-3beta and p38 phosphorylate cyclin D2 on Thr280 to trigger its ubiquitin/proteasome-dependent degradation in hematopoietic cells. 1748 76

Pathways of the molecular pathogenesis of colorectal carcinoma have been extensively studied and molecular lesions during the development of the disease have been revealed. High up in the list of colorectal cancer lesions are APC (adenomatous polyposis coli), K-ras, Smad4 (or DPC4-deleted in pancreatic cancer 4) and p53 genes. All these molecules are part of important pathways for the regulation of cell proliferation and apoptosis and as a result perturbation of these processes lead to carcinogenesis. The ubiquitin-proteasome system (UPS) is comprised of a multi-unit cellular protease system that regulates several dozens of cell proteins after their ligation with the protein ubiquitin. Given that among these proteins are regulators of the cell cycle, apoptosis, angiogenesis, adhesion and cell signalling, this system plays a significant role in cell fate and carcinogenesis. UPS inhibition has been found to be a pre-requisite for apoptosis and is already clinically exploited with the proteasome inhibitor bortezomib in multiple myeloma. Cyclooxygenase-2 (Cox-2) is the inducible form of the enzyme that metabolizes the lipid arachidonic acid to prostaglandin H2, the first step of prostaglandins production. This enzyme is up-regulated in colorectal cancer and in several other cancers. Inhibition of Cox-2 by aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been found to inhibit proliferation of colorectal cancer cells and in epidemiologic studies has been shown to reduce colon polyp formation in genetically predisposed populations and in the general population. NSAIDs have also Cox-independent anti-proliferative effects. Targeted therapies, the result of increasingly understanding carcinogenesis in the molecular level, have entered the field of anti-neoplastic treatment and are used by themselves and in combination with chemotherapy drugs. Combinations of targeted drugs have started also to be investigated. This article reviews the molecular pathogenesis of colorectal cancer, the roles of UPS and Cox-2 in it and puts forward a rational for their combined inhibition in colorectal cancer treatment.
 ...
PMID:Pathogenesis of colorectal carcinoma and therapeutic implications: the roles of the ubiquitin-proteasome system and Cox-2. 1748 76

The ubiquitin-proteasome pathway plays a central role in the degradation of proteins involved in several pathways including the cell cycle, cellular proliferation and apoptosis. Bortezomib is the first proteasome inhibitor to enter clinical use, and received approval by the Food and Drug Administration (FDA) for the treatment of patients with multiple myeloma, therefore validating inhibition of the proteasome as an anticancer target. The approval of Bortezomib was based on a large, international, multicenter phase III trial showing its efficacy and safety compared with conventional therapy. Preclinical data also demonstrates the synergistic effect of bortezomib with other chemotherapeutic agents and its ability to overcome drug resistance. Since then several other proteasome inhibitors have been developed. The anti-tumor activities of bortezomib have been attributed to its effect on pro-apoptotic pathways including the inhibition of NF-kappaB and induction of endoplasmic reticulum stress. However, the molecular mechanisms are not fully understood. In this review, we will summarize the molecular mechanism of apoptosis by bortezomib.
 ...
PMID:Targeting the ubiquitin-proteasome pathway in cancer therapy. 1750 61

Targeting the ubiquitin-proteasome pathway has emerged as a potent anticancer strategy. Bortezomib, a specific proteasome inhibitor, has been approved for the treatment of relapsed or refractory multiple myeloma. Multiple myeloma cell survival is highly dependent on Mcl-1 antiapoptotic molecules. In a recent study, proteasome inhibitors induced Mcl-1 accumulation that slowed down their proapoptotic effects. Consequently, we investigated the role of Bcl-2 family members in bortezomib-induced apoptosis. We found that bortezomib induced apoptosis in five of seven human myeloma cell lines (HMCL). Bortezomib-induced apoptosis was associated with Mcl-1 cleavage regardless of Mcl-1L accumulation. Furthermore, RNA interference mediated Mcl-1 decrease and sensitized RPMI-8226 HMCL to bortezomib, highlighting the contribution of Mcl-1 in bortezomib-induced apoptosis. Interestingly, an important induction of Noxa was found in all sensitive HMCL both at protein and mRNA level. Concomitant to Mcl-1 cleavage and Noxa induction, we also found caspase-3, caspase-8, and caspase-9 activation. Under bortezomib treatment, Mcl-1L/Noxa complexes were highly increased, Mcl-1/Bak complexes were disrupted, and there was an accumulation of free Noxa. Finally, we observed a dissociation of Mcl-1/Bim complexes that may be due to a displacement of Bim induced by Noxa. Thus, in myeloma cells, the mechanistic basis for bortezomib sensitivity can be explained mainly by the model in which the sensitizer Noxa can displace Bim, a BH3-only activator, from Mcl-1, thus leading to Bax/Bak activation.
 ...
PMID:Noxa up-regulation and Mcl-1 cleavage are associated to apoptosis induction by bortezomib in multiple myeloma. 1754 23

Proteasome inhibitors are novel antitumor agents against multiple myeloma and other malignancies. Despite the increasing clinical application, the molecular basis of their antitumor effect has been poorly understood due to the involvement of the ubiquitin-proteasome pathway in multiple cellular metabolisms. Here, we show that treatment of cells with proteasome inhibitors has no significant effect on nonhomologous end joining but suppresses homologous recombination (HR), which plays a key role in DNA double-strand break (DSB) repair. In this study, we treat human cells with proteasome inhibitors and show that the inhibition of the proteasome reduces the efficiency of HR-dependent repair of an artificial HR substrate. We further show that inhibition of the proteasome interferes with the activation of Rad51, a key factor for HR, although it does not affect the activation of ATM, gammaH2AX, or Mre11. These data show that the proteasome-mediated destruction is required for the promotion of HR at an early step. We suggest that the defect in HR-mediated DNA repair caused by proteasome inhibitors contributes to antitumor effect, as HR plays an essential role in cellular proliferation. Moreover, because HR plays key roles in the repair of DSBs caused by chemotherapeutic agents such as cisplatin and by radiotherapy, proteasome inhibitors may enhance the efficacy of these treatments through the suppression of HR-mediated DNA repair pathways.
 ...
PMID:Inhibitors of the proteasome suppress homologous DNA recombination in mammalian cells. 1787 93

The oncogene c-maf is frequently overexpressed in multiple myeloma cell lines and patient samples and contributes to increased cellular proliferation in part by inducing cyclin D2 expression. To identify regulators of c-maf, we developed a chemical screen in NIH3T3 cells stably overexpressing c-maf and the cyclin D2 promoter driving luciferase. From a screen of 2400 off-patent drugs and chemicals, we identified glucocorticoids as c-maf-dependent inhibitors of cyclin D2 transactivation. In multiple myeloma cell lines, glucocorticoids reduced levels of c-maf protein without influencing corresponding mRNA levels. Subsequent studies demonstrated that glucocorticoids increased ubiquitination-dependent degradation of c-maf and up-regulated ubiquitin C mRNA. Moreover, ectopic expression of ubiquitin C recapitulated the effects of glucocorticoids, demonstrating regulation of c-maf protein through the abundance of the ubiquitin substrate. Thus, using a chemical biology approach, we identified a novel mechanism of action of glucocorticoids and a novel mechanism by which levels of c-maf protein are regulated by the abundance of the ubiquitin substrate.
 ...
PMID:A chemical biology screen identifies glucocorticoids that regulate c-maf expression by increasing its proteasomal degradation through up-regulation of ubiquitin. 1787 8

Precedent from preclinical experiments coupled with two pivotal phase 2 studies in myeloma has focused attention on a potential role for ubiquitin-proteasome pathway in modulating a number of events that occur commonly in the neoplastic process involving proteins in the regulation of cells cycling, growth and differentiation. This influence is vested in the proteasomes which are large complexes of proteolytic enzymes responsible for degradation of many of these intracellular messengers. Logically interest has centred on molecules having the capacity to influence, by degradation, such molecules and although a number of agents are in development bortezomib is the only one currently in clinical use. Velcade, formerly PS-341, is a novel dipeptide boronic acid capable of reversibly inhibiting the 26S proteasome through a range of activities. The latter are anti-proliferative and proapoptotic with the latter blocking nuclear transcription via NF-kappa B in addition to down regulating adhesion and inhibiting angiogenesis. Additional changes are mediated in protein folding within the endoplasmic reticulum and contribute to cell death. These concepts are given focus by considering their introduction into treatment of lymphoreticular malignancy.
 ...
PMID:Use of novel proteosome inhibitors as a therapeutic strategy in lymphomas current experience and emerging concepts. 1788 Dec 93

The ubiquitin/proteasome (UP) pathway plays a significant role in many important biological functions and alterations in this pathway have been shown to contribute to the pathology of many human diseases, including cancer. Proteasome inhibition has been well established as a rational strategy for the treatment of multiple myeloma and is currently under investigation for the treatment of other haematological malignancies and solid tumours. Recent evidence suggests that proteasome inhibition may also sensitise tumour cells to the actions of both conventional chemotherapy and radiotherapy, suggesting that this pathway may modify clinical response to anticancer therapy. However, conflicting evidence exists as to the roles of the UP pathway in resistance to treatment. This review endeavours to discuss such roles.
 ...
PMID:The putative roles of the ubiquitin/proteasome pathway in resistance to anticancer therapy. 1788 50


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>