Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0178874 (tumor progression)
 40,807 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bioluminescence imaging (BLI) of luciferase reporters in small animal models offers an attractive approach to monitor regulation of gene expression, signal transduction, and protein-protein interactions, as well as following tumor progression, cell engraftment, infectious pathogens, and target-specific drug action. Conventional BLI can be repeated within the same animal after bolus reinjections of a bioluminescent substrate. However, intervals between image acquisitions are governed by substrate pharmacokinetics and excretion, therefore restricting temporal resolution of reinjection protocols to the order of hours, limiting analyses of processes in vivo with short time constants. To eliminate these constraints, we examined use of implanted micro-osmotic pumps for continuous, long-term delivery of bioluminescent substrates. Pump-assisted d-luciferin delivery enabled BLI for > or = 7 days from a variety of luciferase reporters. Pumps allowed direct repetitive imaging at < 5-minute intervals of the pharmacodynamics of proteasome- and IKK-inhibiting drugs in mice bearing tumors stably expressing ubiquitin-firefly luciferase or IkappaBalpha-firefly luciferase fusion reporters. Circadian oscillations in the olfactory bulbs of transgenic rats expressing firefly luciferase under the control of the period1 promoter also were temporally resolved over the course of several days. We conclude that implanted pumps provide reliable, prolonged substrate delivery for high temporal resolution BLI, traversing complications of repetitive substrate injections.
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PMID:Continuous delivery of D-luciferin by implanted micro-osmotic pumps enables true real-time bioluminescence imaging of luciferase activity in vivo. 1744 6

Nedd4-binding partner-1 (N4BP1) has been identified as a protein interactor and a substrate of the homologous to E6AP C terminus (HECT) domain-containing E3 ubiquitin-protein ligase (E3), Nedd4. Here, we describe a previously unrecognized functional interaction between N4BP1 and Itch, a Nedd4 structurally related E3, which contains four WW domains, conferring substrate-binding activity. We show that N4BP1 association with the second WW domain (WW2) of Itch interferes with E3 binding to its substrates. In particular, we found that N4BP1 and p73 alpha, a target of Itch-mediated ubiquitin/proteasome proteolysis, share the same binding site. By competing with p73 alpha for binding to the WW2 domain, N4BP1 reduces the ability of Itch to recruit and ubiquitylate p73 alpha and inhibits Itch autoubiquitylation activity both in in vitro and in vivo ubiquitylation assays. Similarly, both c-Jun and p63 polyubiquitylation by Itch are inhibited by N4BP1. As a consequence, genetic and RNAi knockdown of N4BP1 diminish the steady-state protein levels and significantly impair the transcriptional activity of Itch substrates. Notably, stress-induced induction of c-Jun was impaired in N4BP1(-/-) cells. These results demonstrate that N4BP1 functions as a negative regulator of Itch. In addition, because inhibition of Itch by N4BP1 results in the stabilization of crucial cell death regulators such as p73 alpha and c-Jun, it is conceivable that N4BP1 may have a role in regulating tumor progression and the response of cancer cells to chemotherapy.
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PMID:The Nedd4-binding partner 1 (N4BP1) protein is an inhibitor of the E3 ligase Itch. 1759 38

The proteasome controls a plethora of survival factors in all mammalian cells analyzed to date. Therefore, it is puzzling that proteasome inhibitors such as bortezomib can display a preferential toxicity toward malignant cells. In fact, proteasome inhibitors have the salient feature of promoting a dramatic induction of the proapoptotic protein NOXA in a tumor cell-restricted manner. However, the molecular determinants that control this specific regulation of NOXA are unknown. Here, we show that the induction of NOXA by bortezomib is directly dependent on the oncogene c-MYC. This requirement for c-MYC was found in a variety of tumor cell types, in marked contrast with dispensable roles of p53, HIF-1alpha, and E2F-1 (classical proteasomal targets that can regulate NOXA mRNA under stress). Conserved MYC-binding sites identified at the NOXA promoter were validated by ChIP and reporter assays. Down-regulation of the endogenous levels of c-MYC abrogated the induction of NOXA in proteasome-defective tumor cells. Conversely, forced expression of c-MYC enabled normal cells to accumulate NOXA and subsequently activate cell death programs in response to proteasome blockage. c-MYC is itself a proteasomal target whose levels or function are invariably up-regulated during tumor progression. Our data provide an unexpected function of c-MYC in the control of the apoptotic machinery, and reveal a long sought-after oncogenic event conferring sensitivity to proteasome inhibition.
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PMID:Tumor cell-selective regulation of NOXA by c-MYC in response to proteasome inhibition. 1804 11

The broad range of biological responses elicited by transforming growth factor-beta (TGF-beta) in various types of tissues and cells is mainly determined by the expression level and activity of the effector proteins Smad2 and Smad3. It is not fully understood how the baseline properties of Smad3 are regulated, although this molecule is in complex with many other proteins at the steady state. Here we show that nonactivated Smad3, but not Smad2, undergoes proteasome-dependent degradation due to the concerted action of the scaffolding protein Axin and its associated kinase, glycogen synthase kinase 3-beta (GSK3-beta). Smad3 physically interacts with Axin and GSK3-beta only in the absence of TGF-beta. Reduction in the expression or activity of Axin/GSK3-beta leads to increased Smad3 stability and transcriptional activity without affecting TGF-beta receptors or Smad2, whereas overexpression of these proteins promotes Smad3 basal degradation and desensitizes cells to TGF-beta. Mechanistically, Axin facilitates GSK3-beta-mediated phosphorylation of Smad3 at Thr66, which triggers Smad3 ubiquitination and degradation. Thr66 mutants of Smad3 show altered protein stability and hence transcriptional activity. These results indicate that the steady-state stability of Smad3 is an important determinant of cellular sensitivity to TGF-beta, and suggest a new function of the Axin/GSK3-beta complex in modulating critical TGF-beta/Smad3-regulated processes during development and tumor progression.
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PMID:Axin and GSK3- control Smad3 protein stability and modulate TGF- signaling. 1817 67

Nitric oxide (NO) has been widely recognized as a positive regulator of tumorigenesis and cancer progression through its ability to regulate important proteins in various signal transduction pathways. S-Nitrosylation, or covalent attachment of NO to protein sulphydryl groups, has gained prominence as an important mechanism by which NO modulates physiologic and pathologic cellular responses. In this article, we discuss S-nitrosylation of two key apoptosis-regulatory proteins of the intrinsic and extrinsic death pathways, namely B-cell lymphoma-2 (Bcl-2) and FLICE-inhibitory protein (FLIP). These proteins have been shown to be upregulated in a variety of tumors and have been implicated with cancer chemoresistance through dysregulation of apoptosis. S-Nitrosylation of these proteins precludes their ubiquitination and subsequent degradation by the proteasome, thus accentuating their anti-apoptotic effect which is critical in the context of tumorigenic potential and cancer progression. We propose that such post-translational modifications of proteins by NO may be a general mechanism that tumor cells exploit to tilt the scales towards survival and proliferation by evading cell death.
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PMID:Role of S-nitrosylation in apoptosis resistance and carcinogenesis. 1847 61

Colorectal adenocarcinoma is one of the worldwide leading causes of cancer deaths. Discovery of specific biomarkers for early detection of cancer progression and the identification of underlying pathogenetic mechanisms are important tasks. Global proteomic approaches have thus far been limited by the large dynamic range of molecule concentrations in tissues and the lack of selective enrichment of the low-abundance proteome. We studied paired cancerous and normal clinical tissue specimens from patients with colorectal adenocarcinomas by heparin affinity fractionation enrichment (HAFE) followed by 2-D PAGE and tandem mass spectrometric (MS/MS) identification. Fifty-six proteins were found to be differentially expressed, of which 32 low-abundance proteins were only detectable after heparin affinity enrichment. MS/MS was used to identify 5 selected differentially expressed proteins as proteasome subunit beta type 7 (PSB7), hemoglobin alpha subunit (HBA), peroxiredoxin-1 (PRDX1), argininosuccinate synthase (ASSY), and signal recognition particle 9 kDa protein (SRP9). This is the first proteomic study detecting the differential expression of these proteins in human colorectal cancer tissue. Several of the proteins are functionally related to tissue hypoxia and hypoxic adaptation. The relative specificities of PSB7, PRDX1, and SRP9 overexpression in colon cancer were investigated by Western blot analysis of patients with colon adenocarcinomas and comparison with a control cohort of patients with lung adenocarcinomas. Furthermore, immunohistochemistry on tissue sections was used to define the specific locations of PSB7, PRDX1, and SRP9 up-regulation within heterogeneous primary human tumor tissue. Overexpression of the three proteins was restricted to the neoplastic cancer cell population within the tumors, demonstrating both cytoplasmic and nuclear localization of PSB7 and predominantly cytoplasmic localization of PRDX1 and SRP9. In summary, we describe heparin affinity fractionation enrichment (HAFE) as a prefractionation tool for the study of the human primary tissue proteome and the discovery of PSB7, PRDX1, and SRP9 up-regulation as candidate biomarkers of colon cancer.
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PMID:Proteomic expression analysis of surgical human colorectal cancer tissues: up-regulation of PSB7, PRDX1, and SRP9 and hypoxic adaptation in cancer. 1854 62

The PML tumor suppressor controls growth suppression, induction of apoptosis, and cellular senescence. PML loss occurs frequently in hematopoietic and solid tumors. PML loss often correlates with tumor progression. Casein kinase 2 (CK2) is a stress-activated serine/threonine protein kinase that is oncogenic and frequently overexpressed in human tumor of multiple histological origins. In addition, CK2 overexpression due to gene amplification has been reported to be an adverse prognostic factor in non-small cell lung cancer. At the 5th International Conference on Protein Kinase CK2 in Padova, Italy, we reviewed our recent findings that PML undergoes ubiquitin/proteasome-mediated degradation in immortalized and tumor derived cell lines. PML degradation depends on direct CK2 phosphorylation of PML Ser517. PML mutants that are resistant to CK2 phosphorylation display increased tumor suppressive functions in assays measuring apoptosis, replicative senescence, and in xenograft models. More significantly, CK2 pharmacological inhibition enhances PML tumor suppressive property. These data identify a key post-translational mechanism that controls PML protein levels in cancer cells and suggest that CK2 inhibitors may be beneficial anti-cancer drugs.
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PMID:CK2 mediates phosphorylation and ubiquitin-mediated degradation of the PML tumor suppressor. 1856 54

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.
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PMID:ICER expression inhibits leukemia phenotype and controls tumor progression. 1878 39

The purpose of the present study was to evaluate the potency of the proteasome inhibitor bortezomib +/- gemcitabine in vitro and in vivo in pancreatic carcinoma. It could be shown that bortezomib induced apoptosis and inhibited proliferation of pancreatic carcinoma very efficiently in vitro. In contrast, in an orthotopic pancreatic adenocarcinoma mouse model, gemcitabine treatment inhibited tumor growth, whereas bortezomib promoted it. Bortezomib-treated animals showed significantly higher tumor burden compared with gemcitabine-treated and control animals, although bortezomib was locally active and induced a decrease of proteasome activity, which was most pronounced following the simultaneous administration of gemcitabine. Also, tumor progression was not caused by immunosuppression as a result of proteasome inhibition. Interestingly, anti-CD31 staining of tumors showed that angiogenesis was significantly increased in the tumors of bortezomib-treated mice compared with the tumors of control animals. In addition, bortezomib resulted an increase of pericytes, vascular endothelial growth factor, RGS-5, and hypoxia-inducible factor-1alpha in the tumor. Although this study supports efficacy of bortezomib against pancreatic carcinoma in vitro, it strongly indicates that bortezomib therapy has a significant tumor-promoting effect in vivo by induction of angiogenesis. The data are in accordance with the complete failure of bortezomib in a phase II trial for this indication. Choosing the right schedule of gemcitabine and bortezomib showed some synergistic effects, but the gain might not be big enough to compensate the potentially detrimental effects.
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PMID:Bortezomib is ineffective in an orthotopic mouse model of pancreatic adenocarcinoma. 1900 44

Hypoxia is a dynamic feature of the tumor microenvironment that contributes to drug resistance and cancer progression. We previously showed that components of the unfolded protein response (UPR), elicited by endoplasmic reticulum (ER) stress, are also activated by hypoxia in vitro and in vivo animal and human patient tumors. Here, we report that ER stressors, such as thapsigargin or the clinically used proteasome inhibitor bortezomib, exhibit significantly higher cytotoxicity toward hypoxic compared with normoxic tumor cells, which is accompanied by enhanced activation of UPR effectors in vitro and UPR reporter activity in vivo. Treatment of cells with the translation inhibitor cycloheximide, which relieves ER load, ameliorated this enhanced cytotoxicity, indicating that the increased cytotoxicity is ER stress-dependent. The mode of cell death was cell type-dependent, because DLD1 colorectal carcinoma cells exhibited enhanced apoptosis, whereas HeLa cervical carcinoma cells activated autophagy, blocked apoptosis, and eventually led to necrosis. Pharmacologic or genetic ablation of autophagy increased the levels of apoptosis. These results show that hypoxic tumor cells, which are generally more resistant to genotoxic agents, are hypersensitive to proteasome inhibitors and suggest that combining bortezomib with therapies that target the normoxic fraction of human tumors can lead to more effective tumor control.
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PMID:Preferential cytotoxicity of bortezomib toward hypoxic tumor cells via overactivation of endoplasmic reticulum stress pathways. 1901 Sep 6


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