Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To investigate potential interplay between the SUMO1 (small ubiquitin-related modifier-1) and ubiquitin pathways of post-translational protein modification, we examined aspects of their localization and conjugation status during proteasome inhibition. Our results indicate that these pathways converge upon the discrete sub-nuclear domains known as PML (promyelocytic leukaemia protein) NBs (nuclear bodies). Proteasome inhibition generated an increased number of PML bodies, without any obvious increase in size. Using a cell line that constitutively expresses an epitope-tagged version of SUMO1, which was incorporated into high-molecular-mass conjugates, we observed SUMO1 accumulating in clusters around a subset of the NBs. Nuclear ubiquitin was initially observed in numerous speckles and foci, which bore no relationship to PML NBs in the absence of proteasome inhibition. However, during proteasome inhibition, total ubiquitin-conjugated species increased in the cell, as judged by Western blotting. Concomitantly the number of nuclear ubiquitin clusters decreased, and were almost quantitatively associated with the PML NBs, co-localizing with the SUMO-conjugated pool. Proteasome inhibition depleted the pool of free SUMO1 in the cell. Reversal of proteasome inhibition in the presence or absence of protein synthesis demonstrated that free SUMO1 was regenerated from the conjugated pool. The results indicate that a significant fraction of the free SUMO1 pool could be accounted for by recycling from the conjugated pool and indeed it may be that, as for ubiquitin, SUMO1 needs to be removed from conjugated species prior to processing by the proteasome. Taken together with other recent reports on the proteasome and PML NBs, these results suggest that the PML NBs may play an important role in integrating these pathways.
 ...
PMID:Comparison of the SUMO1 and ubiquitin conjugation pathways during the inhibition of proteasome activity with evidence of SUMO1 recycling. 1611 25

Inhibition of p38 kinase blocks the production of tumor-promoting factors in the multiple myeloma (MM) bone marrow microenvironment. Proteasome inhibitors MG132 and bortezomib have been shown to have direct cytotoxic effects on MM cells. We show that a selective inhibitor of p38alpha, SCIO-469, enhances the ability of MG132 and bortezomib to induce the apoptosis of MM cells. Previously, we showed that p38 inhibition with SCIO-469 enhances MM cytotoxicity of bortezomib by inhibiting the transient expression and phosphorylation of Hsp27, a downstream target of p38. Here we show that continued treatment of MM cells with bortezomib leads to a SCIO-469-enhanced downregulation of Hsp27 and to increased MM apoptosis. Furthermore, we show that p38 inhibition enhances the bortezomib-induced MM apoptosis by upregulation of p53 and downregulation of Bcl-X(L) and Mcl-1. In a mouse xenograft plasmacytoma model of MM, we found that inhibiting p38 augments the effects of bortezomib in decreasing MM tumor growth in vivo. Thus, in addition to its role in suppressing an activated MM microenvironment, co-treatment with a p38 inhibitor, such as SCIO-469, may enhance the cytotoxicity of bortezomib by modulating pro-apoptotic and anti-apoptotic factors in MM cells, suggesting great potential for co-therapy.
Leukemia 2006 Jun
PMID:Inhibition of p38alpha MAPK enhances proteasome inhibitor-induced apoptosis of myeloma cells by modulating Hsp27, Bcl-X(L), Mcl-1 and p53 levels in vitro and inhibits tumor growth in vivo. 1661 27

Proteasome inhibitors are emerging as effective drugs for the treatment of multiple myeloma and possibly certain subtypes of non-Hodgkin's lymphoma. Bortezomib (Velcade) is the first proteasome inhibitor proven to be clinically useful and will soon be followed by a second generation of small molecule inhibitors with improved pharmacological properties. Although it is now understood that certain types of malignancies have an exquisite dependence on a functional proteasome for their survival, the underlying reason(s) remain unclear as of now. In this context, addiction to nuclear factor-kappaB (NF-kappaB)-induced survival signals, activation of the unfolded protein response as well as a reduced proteasomal activity in differentiated plasma cells have all been proposed to justify proteasome inhibitors' activity in susceptible tissues. In addition to their anticancer properties, bortezomib and related drugs modulate inflammatory and immune responses by affecting function and survival of immune cells such as lymphocytes and dendritic cells. The present review offers an overview of the biological effects that have been involved in proteasome inhibitors' antitumor activity and suggests prospective future applications for these drugs based on their recently characterized anti-inflammatory and immunomodulatory effects.
Leukemia 2007 Jan
PMID:Proteasome inhibitors: antitumor effects and beyond. 1709 16

Glucocorticoids induce apoptosis in chronic lymphocytic leukemia (CLL) cells through a caspase-dependent mechanism. However, their mechanism of action remains unknown. We have studied the regulation of the proapoptotic BH3-only Bcl-2 interacting mediator of cell death (BIM) in CLL cells. We demonstrate that glucocorticoids upregulate BIM at protein and mRNA levels. We have investigated the ability of different survival signals, such as 12-O-tetradecanoylphorbol 13-acetate (TPA), stromal cell-derived factor-1alpha (SDF-1alpha), interleukin 4 (IL-4) and B-cell receptor (BCR) activation, to influence the levels of BIM and its induction by glucocorticoids. TPA downregulates BIM(EL) by extracellular signal-regulated kinase (ERK)-mediated BIM phosphorylation and further proteasome-mediated degradation. However, SDF-1alpha and BCR activation induce transient BIM phosphorylation, without protein degradation. Proteasome inhibitors do not modify the levels of BIM with respect to untreated cells. However, they induce apoptosis and inhibit TPA-induced BIM(EL) degradation, leading to its accumulation. In conclusion, the results implicate BIM in glucocorticoid-induced apoptosis in CLL cells. BIM(EL) phosphorylation through the ERK pathway targets the protein for proteasomal degradation.
Leukemia 2007 Feb
PMID:Regulation of the proapoptotic BH3-only protein BIM by glucocorticoids, survival signals and proteasome in chronic lymphocytic leukemia cells. 1715 1

Proteasome inhibitors represent a new class of antineoplastic drugs that are considered in the treatment of haematological malignancies. We compared the effects of the reversible proteasome inhibitor bortezomib (Velcade) and the epoxomicin derivative PR-171, an irreversible inhibitor, on primary human acute myeloid leukaemia (AML) cells. Both drugs inhibited autocrine- and cytokine-dependent proliferation of primary AML blasts when tested at nanomolar levels (0.1-100 nmol/l). The antiproliferative effect was independent of basal chymotrypsin-like proteasome activity (showing a 20-fold variation between patients), genetic abnormalities, morphological differentiation and CD34 expression when testing a large group of consecutive patients (n = 54). The effect was retained in cocultures with bone marrow stromal cells. In addition, both drugs enhanced apoptosis. The effect of PR-171 could be detected at lower concentrations than for bortezomib, especially when testing the influence on clonogenic AML cell proliferation. Both drugs had divergent effects on AML cells' constitutive cytokine release. Furthermore, both drugs caused a decrease in proliferation and viability when tested in combination with idarubicin or cytarabine. An antiproliferative effect on primary human acute lymphoblastic leukaemia cells was also detected. We conclude that nanomolar levels of the proteasome inhibitors tested had dose-dependent antiproliferative and proapoptotic effects on primary AML cells in vitro.
 ...
PMID:The proteasome inhibitors bortezomib and PR-171 have antiproliferative and proapoptotic effects on primary human acute myeloid leukaemia cells. 1734 Dec 67

Renal impairment is associated with poor prognosis in multiple myeloma (MM). This subgroup analysis of the phase 3 Assessment of Proteasome Inhibition for Extending Remissions (APEX) study of bortezomib vs high-dose dexamethasone assessed efficacy and safety in patients with relapsed MM with varying degrees of renal impairment (creatinine clearance (CrCl) <30, 30-50, 51-80 and >80 ml min(-1)). Time to progression (TTP), overall survival (OS) and safety were compared between subgroups with CrCl < or =50 ml min(-1) (severe-to-moderate) and >50 ml min(-1) (no/mild impairment). Response rates with bortezomib were similar (36-47%) and time to response rapid (0.7-1.6 months) across subgroups. Although the trend was toward shorter TTP/OS in bortezomib patients with severe-to-moderate vs no/mild impairment, differences were not significant. OS was significantly shorter in dexamethasone patients with CrCl < or =50 vs >50 ml min(-1) (P=0.003), indicating that bortezomib is more effective than dexamethasone in overcoming the detrimental effect of renal impairment. Safety profile of bortezomib was comparable between subgroups. With dexamethasone, grade 3/4 adverse events (AEs), serious AEs and discontinuations for AEs were significantly elevated in patients with CrCl < or =50 vs >50 ml min(-1). These results indicate that bortezomib is active and well tolerated in patients with relapsed MM with varying degrees of renal insufficiency. Efficacy/safety were not substantially affected by severe-to-moderate vs no/mild impairment.
Leukemia 2008 Apr
PMID:Efficacy and safety of bortezomib in patients with renal impairment: results from the APEX phase 3 study. 1820 40

Many cellular processes converge on the proteasome, and its key regulatory role is increasingly being recognized. Proteasome inhibition allows the manipulation of many cellular pathways including apoptotic and cell cycle mechanisms. The proteasome inhibitor bortezomib has enhanced responses in newly diagnosed patients with myeloma and provides a new line of therapy in relapsed and refractory patients. Malignant cells are more sensitive to proteasome inhibition than normal haematopoietic cells. Proteasome inhibition enhances many conventional therapies and its role in leukaemia is promising.
 ...
PMID:The therapeutic potential of the proteasome in leukaemia. 1832 39

The 26S proteasome regulates the degradation of many proteins involved in cell cycle control, apoptosis, and tumor growth. The inhibition of the proteasome by specific inhibitors is a viable target for anti-tumor therapy Most prominently, the proteasome inhibitor bortezomib (Velcade) was approved by the U.S. Food and Drug Administration (FDA) for the treatment of relapsed or refractory multiple myeloma in adults, and is presently considered for several other types of cancer including pediatric malignancies. The first clinical trials by the Children's Oncology Group (COG) were conducted with bortezomib for the treatment of refractory solid tumors and refractory leukemia. Proteasome inhibitors are a promising new class of therapeutics that should be further explored in combination with other chemotherapeutic agents for the treatment of pediatric cancer patients.
 ...
PMID:Proteasome inhibitors in pediatric cancer treatment. 1885 1

Proteasome inhibition has emerged as a powerful option for the treatment of a number of malignancies including leukemias. However, Bortezomib showed limited single-agent activity for patients with leukemia. Here, we report for the first time that Bortezomib up-regulated a novel antiapoptotic protein, BAG3, in human leukemic cells. BAG3 gene knockdown with shRNA greatly potentiated the generation of apoptosis by Bortezomib in leukemia cells. Furthermore, BAG3 silencing enhanced the antitumor activity of Bortezomib dramatically in a nude mouse model. Our results indicate that knocking down BAG3 gene is a promising new approach to enhance the therapeutic potency of Bortezomib in leukemia.
 ...
PMID:BAG3 gene silencing sensitizes leukemic cells to Bortezomib-induced apoptosis. 1911 44

New chemotherapeutic agents are still required to further optimise treatment of leukemia patients. Proteasome inhibition by bortezomib, PR-171 (carfilzomib) and NPI-0052 (salinosporamide A) has been successfully used for the treatment of multiple myeloma and mantle cell lymphoma and is considered also as novel treatment strategy in leukemia. Combination of proteasome inhibitors bortezomib and NPI-0052 induces synergistic anti-multiple myeloma activity both in vitro using multiple myeloma cells and in vivo in a human plasmacytoma xenograft mouse model. Cell death resulting from proteasome inhibition requires caspase activation and increased levels of reactive oxygen species. While bortezomib induces several caspases, NPI-0052 activates predominantly caspase-8-dependent pathway. We studied the effect of bortezomib (10 nM) on DNA synthesis and apoptosis in human acute myeloid cell lines KASUMI-1, ML-1, ML-2 and CTV-1 cells. Bortezomib was potent inhibitor of DNA synthesis in all four types of leukemia cells and induced apoptosis in KASUMI-1, ML-2 and CTV-1 cells but not in ML-1 cells. Other research groups showed that histone deacetylase inhibitors (valproic acid or benzamide derivative MS-275) in combination with NPI-0052 or PR-171 induced greater levels of acute leukemia cell death than in combination with bortezomib. Proteasome inhibition as monotherapy and its combination with many conventional therapies as novel treatment strategies in leukemia are promising. Malignant cells are more sensitive to this treatment than normal hematopoietic cells.
 ...
PMID:Antiproliferative and proapoptotic effects of proteasome inhibitors and their combination with histone deacetylase inhibitors on leukemia cells. 1927 78


<< Previous 1 2 3 4 Next >>