scholarly journals BNIP3 Is an RB/E2F Target Gene Required for Hypoxia-Induced Autophagy

2007 ◽  
Vol 27 (17) ◽  
pp. 6229-6242 ◽  
Author(s):  
Kristin Tracy ◽  
Benjamin C. Dibling ◽  
Benjamin T. Spike ◽  
James R. Knabb ◽  
Paul Schumacker ◽  
...  
Keyword(s):  
Cell Death ◽  
Tumor Suppressor ◽  
Transcriptional Repression ◽  
Fetal Liver ◽  
Hypoxia Inducible Factor ◽  
Nutrient Deprivation ◽  
Primary Mouse ◽  
Direct Target ◽  
Nonapoptotic Cell Death

ABSTRACT Hypoxia and nutrient deprivation are environmental stresses governing the survival and adaptation of tumor cells in vivo. We have identified a novel role for the Rb tumor suppressor in protecting against nonapoptotic cell death in the developing mouse fetal liver, in primary mouse embryonic fibroblasts, and in tumor cell lines. Loss of pRb resulted in derepression of BNip3, a hypoxia-inducible member of the Bcl-2 superfamily of cell death regulators. We identified BNIP3 as a direct target of pRB/E2F-mediated transcriptional repression and showed that pRB attenuates the induction of BNIP3 by hypoxia-inducible factor to prevent autophagic cell death. BNIP3 was essential for hypoxia-induced autophagy, and its ability to promote autophagosome formation was enhanced under conditions of nutrient deprivation. Knockdown of BNIP3 reduced cell death, and remaining deaths were necrotic in nature. These studies identify BNIP3 as a key regulator of hypoxia-induced autophagy and suggest a novel role for the RB tumor suppressor in preventing nonapoptotic cell death by limiting the extent of BNIP3 induction in cells.

scholarly journals E4F1 deficiency results in oxidative stress–mediated cell death of leukemic cells

2011 ◽  
Vol 208 (7) ◽  
pp. 1403-1417 ◽  
Author(s):  
Elodie Hatchi ◽  
Genevieve Rodier ◽  
Matthieu Lacroix ◽  
Julie Caramel ◽  
Olivier Kirsh ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Lines ◽  
Myeloid Leukemia ◽  
Tumor Regression ◽  
Fetal Liver ◽  
Leukemia Cell ◽  
Leukemic Cells ◽  
Viral Oncoprotein ◽  
Mitochondrial Defects

The multifunctional E4F1 protein was originally discovered as a target of the E1A viral oncoprotein. Growing evidence indicates that E4F1 is involved in key signaling pathways commonly deregulated during cell transformation. In this study, we investigate the influence of E4F1 on tumorigenesis. Wild-type mice injected with fetal liver cells from mice lacking CDKN2A, the gene encoding Ink4a/Arf, developed histiocytic sarcomas (HSs), a tumor originating from the monocytic/macrophagic lineage. Cre-mediated deletion of E4F1 resulted in the death of HS cells and tumor regression in vivo and extended the lifespan of recipient animals. In murine and human HS cell lines, E4F1 inactivation resulted in mitochondrial defects and increased production of reactive oxygen species (ROS) that triggered massive cell death. Notably, these defects of E4F1 depletion were observed in HS cells but not healthy primary macrophages. Short hairpin RNA–mediated depletion of E4F1 induced mitochondrial defects and ROS-mediated death in several human myeloid leukemia cell lines. E4F1 protein is overexpressed in a large subset of human acute myeloid leukemia samples. Together, these data reveal a role for E4F1 in the survival of myeloid leukemic cells and support the notion that targeting E4F1 activities might have therapeutic interest.

scholarly journals HIF-1–dependent repression of equilibrative nucleoside transporter (ENT) in hypoxia

2005 ◽  
Vol 202 (11) ◽  
pp. 1493-1505 ◽  
Author(s):  
Holger K. Eltzschig ◽  
Parween Abdulla ◽  
Edgar Hoffman ◽  
Kathryn E. Hamilton ◽  
Dionne Daniels ◽  
...  
Keyword(s):  
Transcriptional Repression ◽  
Molecular Mechanisms ◽  
Hypoxia Inducible Factor ◽  
Nucleoside Transporter ◽  
In Vivo Models ◽  
Equilibrative Nucleoside Transporter ◽  
Hypoxia Inducible Factor 1 ◽  
And Function

Extracellular adenosine (Ado) has been implicated as central signaling molecule during conditions of limited oxygen availability (hypoxia), regulating physiologic outcomes as diverse as vascular leak, leukocyte activation, and accumulation. Presently, the molecular mechanisms that elevate extracellular Ado during hypoxia are unclear. In the present study, we pursued the hypothesis that diminished uptake of Ado effectively enhances extracellular Ado signaling. Initial studies indicated that the half-life of Ado was increased by as much as fivefold after exposure of endothelia to hypoxia. Examination of expressional levels of the equilibrative nucleoside transporter (ENT)1 and ENT2 revealed a transcriptionally dependent decrease in mRNA, protein, and function in endothelia and epithelia. Examination of the ENT1 promoter identified a hypoxia inducible factor 1 (HIF-1)–dependent repression of ENT1 during hypoxia. Using in vitro and in vivo models of Ado signaling, we revealed that decreased Ado uptake promotes vascular barrier and dampens neutrophil tissue accumulation during hypoxia. Moreover, epithelial Hif1α mutant animals displayed increased epithelial ENT1 expression. Together, these results identify transcriptional repression of ENT as an innate mechanism to elevate extracellular Ado during hypoxia.

scholarly journals Diverse Effects of Mutations in Exon II of the von Hippel-Lindau (VHL) Tumor Suppressor Gene on the Interaction of pVHL with the Cytosolic Chaperonin and pVHL-Dependent Ubiquitin Ligase Activity

2002 ◽  
Vol 22 (6) ◽  
pp. 1947-1960 ◽  
Author(s):  
William J. Hansen ◽  
Michael Ohh ◽  
Javid Moslehi ◽  
Keiichi Kondo ◽  
William G. Kaelin ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Ubiquitin Ligase ◽  
Hypoxia Inducible Factor ◽  
Detectable Effect ◽  
Missense Mutations ◽  
Subsequent Formation ◽  
Von Hippel Lindau ◽  
Ubiquitin Ligase Activity

ABSTRACT We examined the biogenesis of the von Hippel-Lindau (VHL) tumor suppressor protein (pVHL) in vitro and in vivo. pVHL formed a complex with the cytosolic chaperonin containing TCP-1 (CCT or TRiC) en route to assembly with elongin B/C and the subsequent formation of the VCB-Cul2 ubiquitin ligase. Blocking the interaction of pVHL with elongin B/C resulted in accumulation of pVHL within the CCT complex. pVHL present in purified VHL-CCT complexes, when added to rabbit reticulocyte lysate, proceeded to form VCB and VCB-Cul2. Thus, CCT likely functions, at least in part, by retaining VHL chains pending the availability of elongin B/C for final folding and/or assembly. Tumor-associated mutations within exon II of the VHL syndrome had diverse effects upon the stability and/or function of pVHL-containing complexes. First, a pVHL mutant lacking the entire region encoded by exon II did not bind to CCT and yet could still assemble into complexes with elongin B/C and elongin B/C-Cul2. Second, a number of tumor-derived missense mutations in exon II did not decrease CCT binding, and most had no detectable effect upon VCB-Cul2 assembly. Many exon II mutants, however, were found to be defective in the binding to and subsequent ubiquitination of hypoxia-inducible factor 1α (HIF-1α), a substrate of the VCB-Cul2 ubiquitin ligase. We conclude that the selection pressure to mutate VHL exon II during tumorigenesis does not relate to loss of CCT binding but may reflect quantitative or qualitative defects in HIF binding and/or in pVHL-dependent ubiquitin ligase activity.

scholarly journals Role of Promyelocytic Leukemia (Pml) Protein in Tumor Suppression

2001 ◽  
Vol 193 (4) ◽  
pp. 521-530 ◽  
Author(s):  
Eduardo M. Rego ◽  
Zhu-Gang Wang ◽  
Daniela Peruzzi ◽  
Le-Zhen He ◽  
Carlos Cordon-Cardo ◽  
...  
Keyword(s):  
Cell Death ◽  
Tumor Suppressor ◽  
Programmed Cell Death ◽  
Retinoic Acid Receptor ◽  
Nuclear Body ◽  
Promyelocytic Leukemia ◽  
Cathepsin G ◽  
Putative Tumor Suppressor Gene ◽  
Cancer Pathogenesis

The promyelocytic leukemia (PML) gene encodes a putative tumor suppressor gene involved in the control of apoptosis, which is fused to the retinoic acid receptor α (RARα) gene in the vast majority of acute promyelocytic leukemia (APL) patients as a consequence of chromosomal translocations. The PMLRARα oncoprotein is thought to antagonize the function of PML through its ability to heterodimerize with and delocalize PML from the nuclear body. In APL, this may be facilitated by the reduction to heterozygosity of the normal PML allele. To determine whether PML acts as a tumor suppressor in vivo and what the consequences of deregulated programmed cell death in leukemia and epithelial cancer pathogenesis are, we crossed PML−/− mice with human cathepsin G (hCG)-PMLRARα or mammary tumor virus (MMTV)/neu transgenic mice (TM), models of leukemia and breast cancer, respectively. The progressive reduction of the dose of PML resulted in a dramatic increase in the incidence of leukemia, and in an acceleration of leukemia onset in PMLRARα TM. By contrast, PML inactivation did not affect neu-induced tumorigenesis. In hemopoietic cells from PMLRARα TM, PML inactivation resulted in impaired response to differentiating agents such as RA and vitamin D3 as well as in a marked survival advantage upon proapoptotic stimuli. These results demonstrate that: (a) PML acts in vivo as a tumor suppressor by rendering the cells resistant to proapoptotic and differentiating stimuli; (b) PML haploinsufficiency and the functional impairment of PML by PMLRARα are critical events in APL pathogenesis; and (c) aberrant control of programmed cell death plays a differential role in solid tumor and leukemia pathogenesis.

Synergistic and selective inhibition of NSCLC cell growth via a caspase-independent cell death pathway by tumor suppressor 101F6 nanoparticles plus vitamin C in vitro and in vivo

2006 ◽  
Vol 24 (18_suppl) ◽  
pp. 13086-13086
Author(s):  
S. Ohtani ◽  
K. Ueda ◽  
G. Jayanchandran ◽  
K. Xu ◽  
J. D. Minna ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Growth ◽  
Tumor Suppressor ◽  
Vitamin C ◽  
Tumor Cells ◽  
Nsclc Cell ◽  
Normal Lung ◽  
Human Nsclc

13086 Background: 101F6 is a candidate tumor suppressor gene on chromosome 3p21.3, a site of allele loss and genomic alterations were frequently found in many human cancers. We previously showed that enforced expression of wt-101F6 by adenoviral virus significantly inhibited tumor cell growth in 3p21.3-deficient NSCLC cells in vitro and in vivo. How 101F6 exerts this effect is largely unknown. Using a computer-aided structural and functional modeling, we recently identified 101F6 as a member of cytochrome b-561 protein family, which is involved in the regeneration of vitamin C. We hypothesized that under normal physiologic conditions, 101F6 protects cells from oxidative damage by regenerating antioxidant vitamin C and that in 101F6-deficient tumor cells, exogenous 101F6 facilitates vitamin C-mediated cytotoxic H2O2 formation. Methods and Results: We examined endogenous 101F6 expression in human NSCLC cell lines and tissue samples. All normal lung bronchial epithelial cells and fibroblasts but few lung cancers expressed 101F6. We investigated the combined effect of 101F6 and vitamin C on the cell growth: a nanoparticle-mediated wt-101F6 gene transfer plus a sub-pharmacologic concentration of vitamin C synergistically inhibited 3p21.3-deficient NSCLC cell growth but did not affect normal cell growth. We also used a human NSCLC H322 orthotopic lung tumor xenograft mouse model to evaluate the therapeutic efficacy of systemic injection of 101F6 nanoparticles and intraperitoneal injection of vitamin C. The growth of lung tumors was synergistically inhibited by the combination treatment (p<0.001). Furthermore, exogenous 101F6 promoted intracellular vitamin C uptake, leading to the vitamin C-mediated accumulation of H2O2 in the tumor cells, and these two agents synergistically killed the cells through caspase-independent apoptosis and autophagy cell death pathways. Conclusions: The synergistic and selective antitumor effect of 101F6 nanoparticles plus vitamin C may offer a useful tool for lung cancer prevention and intervention. This abstract is supported by grants from NCI (SPORE P50CA70907) and DOD (TARGET, DAMD17002–1-0706). No significant financial relationships to disclose.

scholarly journals Transcriptional Repression of the Neurofibromatosis-1 Tumor Suppressor by the t(8;21) Fusion Protein

2005 ◽  
Vol 25 (14) ◽  
pp. 5869-5879 ◽  
Author(s):  
Genyan Yang ◽  
Waleed Khalaf ◽  
Louis van de Locht ◽  
Joop H. Jansen ◽  
Meihua Gao ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Fusion Protein ◽  
Transcriptional Repression ◽  
Genetic Disorder ◽  
Suppressor Gene ◽  
Juvenile Myelomonocytic Leukemia ◽  
Increased Risk ◽  
Myeloid Progenitor Cells ◽  
Macrophage Colony

ABSTRACT Von Recklinghausen's disease is a relatively common familial genetic disorder characterized by inactivating mutations of the Neurofibromatosis-1 (NF1) gene that predisposes these patients to malignancies, including an increased risk for juvenile myelomonocytic leukemia. However, NF1 mutations are not common in acute myeloid leukemia (AML). Given that the RUNX1 transcription factor is the most common target for chromosomal translocations in acute leukemia, we asked if NF1 might be regulated by RUNX1. In reporter assays, RUNX1 activated the NF1 promoter and cooperated with C/EBPα and ETS2 to activate the NF1 promoter over 80-fold. Moreover, the t(8;21) fusion protein RUNX1-MTG8 (R/M), which represses RUNX1-regulated genes, actively repressed the NF1 promoter. R/M associated with the NF1 promoter in vivo and repressed endogenous NF1 gene expression. In addition, similar to loss of NF1, R/M expression enhanced the sensitivity of primary myeloid progenitor cells to granulocyte-macrophage colony-stimulating factor. Our results indicate that the NF1 tumor suppressor gene is a direct transcriptional target of RUNX1 and the t(8;21) fusion protein, suggesting that suppression of NF1 expression contributes to the molecular pathogenesis of AML.

scholarly journals The ARF tumor suppressor prevents chromosomal instability and ensures mitotic checkpoint fidelity through regulation of Aurora B

2014 ◽  
Vol 25 (18) ◽  
pp. 2761-2773 ◽  
Author(s):  
Eric M.C. Britigan ◽  
Jun Wan ◽  
Lauren M. Zasadil ◽  
Sean D. Ryan ◽  
Beth A. Weaver
Keyword(s):  
Tumor Suppressor ◽  
Mitotic Checkpoint ◽  
Aurora B ◽  
Multipolar Spindles ◽  
Primary Mouse ◽  
The Common ◽  
Additional Tumor ◽  
Cdkn2a Locus

The ARF tumor suppressor is part of the CDKN2A locus and is mutated or undetectable in numerous cancers. The best-characterized role for ARF is in stabilizing p53 in response to cellular stress. However, ARF has tumor suppressive functions outside this pathway that have not been fully defined. Primary mouse embryonic fibroblasts (MEFs) lacking the ARF tumor suppressor contain abnormal numbers of chromosomes. However, no role for ARF in cell division has previously been proposed. Here we demonstrate a novel, p53-independent role for ARF in the mitotic checkpoint. Consistent with this, loss of ARF results in aneuploidy in vitro and in vivo. ARF−/− MEFs exhibit mitotic defects including misaligned and lagging chromosomes, multipolar spindles, and increased tetraploidy. ARF−/− cells exhibit overexpression of Mad2, BubR1, and Aurora B, but only overexpression of Aurora B phenocopies mitotic defects observed in ARF−/− MEFs. Restoring Aurora B to near-normal levels rescues mitotic phenotypes in cells lacking ARF. Our results define an unexpected role for ARF in chromosome segregation and mitotic checkpoint function. They further establish maintenance of chromosomal stability as one of the additional tumor-suppressive functions of ARF and offer a molecular explanation for the common up-regulation of Aurora B in human cancers.

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