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

---

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

Single-agent bortezomib, a potent, selective and reversible inhibitor of the 26S proteasome, has demonstrated clinical efficacy in relapsed and refractory mantle cell lymphoma (MCL). Objective response is achieved in up to 45% of the patients; however, complete remission rates are low and duration of response proved to be short. These limitations may be overcome by combining proteasome inhibition with conventional chemotherapy. Here we present two case reports and in vitro data suggesting synergistic efficacy of bortezomib combined with cytarabine in MCL. Interestingly, efficacy in vitro correlated with sequence of treatment, indicating that pretreatment with cytarabine, followed by proteasome inhibition, may be the preferred approach.
Leukemia 2007 Mar
PMID:Sequence-dependent synergy of the proteasome inhibitor bortezomib and cytarabine in mantle cell lymphoma. 1726 31

Bortezomib is a potent drug for the treatment of multiple myeloma. Its anti-tumor activity is mediated by proteasome inhibition leading to decreased cell proliferation and induction of apoptosis. However, an unimpaired proteasomal function plays a crucial role for the induction of anti-tumor immunity by dendritic cells (DCs), which are currently used for therapeutic vaccination against various tumors including myeloma. In the present study, we investigated the impact of bortezomib on the immunostimulatory capacity of 6-sulfo LacNAc (slan) DCs, which represent a major subset of human blood DCs. We demonstrated that this proteasome inhibitor efficiently impairs the spontaneous in vitro maturation of slanDCs and the release of tumor necrosis factor (TNF)-alpha as well as interleukin (IL)-12 upon lipopolysaccharide (LPS) stimulation. Functional data revealed that bortezomib profoundly inhibits slanDC-induced proliferation and differentiation of CD4(+) T cells. In addition, the capacity of slanDCs to promote interferon-gamma secretion and tumor-directed cytotoxicity of natural killer (NK) cells is markedly impaired by bortezomib. These results provide evidence that bortezomib significantly reduces the ability of native human blood DCs to regulate innate and adaptive anti-tumor immunity and may have implications for the design of therapeutic strategies combining DC vaccination and bortezomib treatment.
Leukemia 2007 Jul
PMID:Bortezomib significantly impairs the immunostimulatory capacity of human myeloid blood dendritic cells. 1749 70

In multiple myeloma, the overexpression of receptor activator of nuclear factor kappa B (NF-kappaB) ligand (RANKL) leads to the induction of NF-kappaB and activator protein-1 (AP-1)-related osteoclast activation and enhanced bone resorption. The purpose of this study was to examine the molecular and functional effects of proteasome inhibition in RANKL-induced osteoclastogenesis. Furthermore, we aimed to compare the outcome of proteasome versus selective NF-kappaB inhibition using bortezomib (PS-341) and I-kappaB kinase inhibitor PS-1145. Primary human osteoclasts were derived from CD14+ precursors in presence of RANKL and macrophage colony-stimulating factor (M-CSF). Both bortezomib and PS-1145 inhibited osteoclast differentiation in a dose- and time-dependent manner and furthermore, the bone resorption activity of osteoclasts. The mechanisms of action involved in early osteoclast differentiation were found to be related to the inhibition of p38 mitogen-activated protein kinase pathways, whereas the later phase of differentiation and activation occurred due to inhibition of p38, AP-1 and NF-kappaB activation. The AP-1 blockade contributed to significant reduction of osteoclastic vascular endothelial growth factor production. In conclusion, our data demonstrate that proteasomal inhibition should be considered as a novel therapeutic option of cancer-induced lytic bone disease.
Leukemia 2007 Sep
PMID:Bortezomib inhibits human osteoclastogenesis. 1758 12

The effectiveness of T-cell-mediated immunotherapy of cancer depends on both an optimal immunostimulatory context of the therapy and the proper selection with respect to quality and quantity of the targeted tumor-associated antigens (TAA), and, more precisely, the T-cell epitopes contained in these tumor proteins. Our progressing insight in human leukocyte antigen (HLA) class I and class II antigen processing and presentation mechanisms has improved the prediction by reverse immunology of novel cytotoxic T lymphocyte and T-helper cell epitopes within known antigens. Computer algorithms that in silico predict HLA class I and class II binding, proteasome cleavage patterns and transporter associated with antigen processing translocation are now available to expedite epitope identification. The advent of genomics allows a high-throughput screening for tumor-specific transcripts and mutations, with that identifying novel shared and unique TAA. The increasing power of mass spectrometry and proteomics will lead to the direct identification from the tumor cell surface of numerous novel tumor-specific HLA class I and class II presented ligands. Together, the expanded repertoire of tumor-specific T-cell epitopes will enable more precise immunomonitoring and the development of effective epitope-defined adoptive T-cell transfer and multi-epitope-based vaccination strategies targeting epitopes derived from a wider diversity of TAA presented in a broader array of HLA molecules.
Leukemia 2007 Sep
PMID:Identification of T-cell epitopes for cancer immunotherapy. 1761 70

Constitutive activation of nuclear factor-kappaB (NF-kappaB) has been described in patient-derived Reed - Sternberg cells and Hodgkin lymphoma (HL) cell lines and contributes to the proliferation and survival of HL. Therapeutic inhibition of the proteasome with bortezomib may inhibit over-expression of nuclear NF-kappaB by preventing degradation of IkappaB, which sequesters NF-kappaB in the cytoplasm. To evaluate this hypothesis, the Cancer and Leukemia Group B (CALGB) conducted a multi-institutional phase II trial of single agent bortezomib in patients with relapsed or refractory classical HL. Thirty patients received bortezomib 1.3 mg/m(2) on days 1, 4, 8, 11 and every 21 days for a median of 2 cycles (range, 1 - 8). Patients were heavily pre-treated with a median of four prior therapies, and 83% were previously transplanted. No responses were observed, 9 patients had stable disease, and 21 progressed. The median progression-free and overall survivals were 1.4 months [95% CI, (1.28, 1.91)] and 14.8 months [95% CI (11.2, 22.3)], respectively. Grade 3 - 4 adverse events, primarily thrombocytopenia, occurred in 15 patients. Therefore, although well tolerated, 1.3 mg/m(2) bortezomib administered biweekly has no single agent activity in relapsed/refractory classical HL.
...
PMID:Single agent bortezomib in the treatment of relapsed and refractory Hodgkin lymphoma: cancer and leukemia Group B protocol 50206. 1761 59

Mutation of Bcr-Abl is an important mechanism by which chronic myelogenous leukemia (CML) cells become resistant to Gleevec. The T315I mutation is clinically significant since CML cells harboring this mutation are insensitive to Gleevec and other Bcr-Abl-targeted drugs. Identification of new agents capable of effectively killing CML cells with T315I mutation would have important therapeutic implications in Gleevec-resistant CML. Here, we showed that beta-phenylethyl isothiocyanate (PEITC), a natural compound found in vegetables, is effective in killing CML cells expressing T315I BCR-ABL. Treatment of leukemia cell lines harboring wild-type or mutant Bcr-Abl with 10 microM PEITC resulted in an elevated ROS stress and a redox-mediated degradation of the BCR-ABL protein, leading to massive death of the leukemia cells. Antioxidant NAC attenuated the PEITC-induced oxidative stress in CML cells and prevented the degradation of BCR-ABL, caspase-3 activation and cell death. We further showed that the ROS-induced degradation of BCR-ABL was mediated partially by caspase-3 and the proteasome pathway. The ability of PEITC to effectively kill T315I-positive CML cells was further confirmed using primary leukemia cells isolated from CML patients. Our results suggest that PEITC is a promising compound capable of killing Gleevec-resistant CML cells through a ROS-mediated mechanism and warrants further investigations.
Leukemia 2008 Jun
PMID:Effective killing of Gleevec-resistant CML cells with T315I mutation by a natural compound PEITC through redox-mediated mechanism. 1838 54

Chronic lymphocytic leukemia (CLL) is a B-cell lymphoid neoplasm with deregulated apoptosis and overexpression of several antiapoptotic BCL-2 proteins. GX15-070/Obatoclax is a small-molecule BH3 mimetic compound that has shown activity against several hematologic malignancies and solid tumors. In the present work, we report that GX15-070 led to the disruption of BCL-2/BIM and MCL-1/BAK complexes in CLL cells, followed by the activation of the mitochondrial apoptotic pathway. CLL cells showed lower sensitivity to GX15-070 than primary mantle cell lymphoma (MCL) ones, in correlation with higher levels of phosphorylated BCL-2 at serine 70 residue (pBCL-2(Ser70)) in CLL cells. Decrease in BCL-2 phosphorylation by extracellular signal-regulated kinase (ERK)1/2 inhibition increased CLL sensitivity to GX15-070, while blocking BCL-2 dephosphorylation using a PP2A antagonist reduced the activity of this BH3 mimetic. GX15-070 activity was increased by cotreatment with the proteasome inhibitor bortezomib. However, as proteasome inhibition led to the accumulation of phosphorylated BCL-2, the degree of interaction between GX15-070 and bortezomib was regulated by basal pBCL-2(Ser70) levels. These results support the role of BCL-2 phosphorylation as a mechanism of resistance to BH3 mimetic compounds, and demonstrate that combination approaches including ERK inhibitors could enhance BH3 mimetics activity both alone or in combination with proteasome inhibitors.
Leukemia 2008 Sep
PMID:BCL-2 phosphorylation modulates sensitivity to the BH3 mimetic GX15-070 (Obatoclax) and reduces its synergistic interaction with bortezomib in chronic lymphocytic leukemia cells. 1859 39

The inducible cyclic AMP (cAMP) early repressor (ICER) and cAMP response element-binding protein (CREB) are transcriptional regulators of the cAMP-mediated signaling pathway. CREB has been demonstrated to be upregulated in the majority of childhood leukemias contributing to disease progression, whereas ICER, its endogenous repressor, was found to be downregulated. Our research focus has been the function of restored ICER expression. ICER exogenously expressed in cell lines decreases CREB protein level and induces a lowered clonogenic potential in vitro. It decreases the ability of HL60 to invade the extramedullary sites and to promote bone marrow angiogenesis in nonobese diabetic-severe combined immunodeficient mice, demonstrating its potential effects on tumor progression. ICER represses the majority of 96 target genes upregulated by CREB. It binds CRE promoters and controls gene expression restoring the normal regulation of major cellular pathways. ICER is subjected to degradation through a constitutively active form of the extracellular signal-regulated protein kinase, which drives it to the proteasome. We propose that ICER is downregulated in HL60 to preserve CREB overexpression, which disrupts normal myelopoiesis and promotes blast proliferation. These findings define the function of ICER as a tumor suppressor in leukemia. Unbalanced CREB/ICER expression needs to be considered a pathogenetic feature in leukemogenesis. The molecular characterization of this pathway could be useful for novel therapeutic strategies.
Leukemia 2008 Dec
PMID:ICER expression inhibits leukemia phenotype and controls tumor progression. 1878 39

Cyclin D dysregulation and overexpression is noted in the majority of multiple myeloma (MM) patients, suggesting its critical role in MM pathogenesis. Here, we sought to identify the effects of targeting cyclin D in MM. We first confirmed cyclin D mRNA overexpression in 42 of 64 (65%) patient plasma cells. Silencing cyclin D1 resulted in >50% apoptotic cell death suggesting its validity as a potential therapeutic target. We next evaluated P276-00, a clinical-grade small-molecule cyclin-dependent kinase inhibitor as a way to target the cyclins. P276-00 resulted in dose-dependent cytotoxicity in MM cells. Cell-cycle analysis confirmed either growth arrest or caspase-dependent apoptosis; this was preceded by inhibition of Rb-1 phosphorylation with associated downregulation of a range of cyclins suggesting a regulatory role of P276-00 in cell-cycle progression through broad activity. Proliferative stimuli such as interleukin-6, insulin-like growth factor-1 and bone-marrow stromal cell adherence induced cyclins; P276-00 overcame these growth, survival and drug resistance signals. Because the cyclins are substrates of proteasome degradation, combination studies with bortezomib resulted in synergism. Finally, in vivo efficacy of P276-00 was confirmed in an MM xenograft model. These studies form the basis of an ongoing phase I study in the treatment of relapsed/refractory MM.
Leukemia 2009 May
PMID:Preclinical activity of P276-00, a novel small-molecule cyclin-dependent kinase inhibitor in the therapy of multiple myeloma. 1915 76

Resistance towards the proteasome inhibitor bortezomib is poorly understood. We adapted the HL-60, ARH-77 and AMO-1 cell lines (myeloid leukemia, plasmocytoid lymphoma, myeloma) to bortezomib exceeding therapeutic plasma levels, and compared characteristics of the ubiquitin-proteasome system, alternative proteases and the unfolded protein response (UPR) between adapted cells and parental lines. Adapted cells showed increased transcription rates, activities and polypeptide levels of the bortezomib-sensitive beta5, but also of the beta2 proteasome subunit and consistently retained elevated levels of active beta1/beta5-type proteasome subunits in the presence of therapeutic levels of bortezomib. Bortezomib-adapted HL-60 cells showed increased expression and proteasome association of the 11S proteasome activator, and did not accumulate poly-ubiquitinated protein, activate the UPR or UPR-mediated apoptosis in response to bortezomib. The rate of protein biosynthesis was reduced, and the transcription of chaperone genes downmodulated. We did not observe major changes in the activities of TPPII, cathepsins or deubiquitinating proteases. We conclude that different types of bortezomib-adapted cell lines, including myeloma, show similar patterns of changes in the proteasomal machinery which result in residual proteasome activity in the presence of bortezomib and a quantitative balance between protein biosynthesis and destruction.
Leukemia 2009 Jun
PMID:Characterization of the ubiquitin-proteasome system in bortezomib-adapted cells. 1922 32


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

---