Gene Summary

Gene:DDIT4; DNA damage inducible transcript 4
Aliases: Dig2, REDD1, REDD-1
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:DNA damage-inducible transcript 4 protein
Source:NCBIAccessed: 14 March, 2017


What does this gene/protein do?
Show (19)
Pathways:What pathways are this gene/protein implicaed in?
Show (1)

Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 14 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Protein Kinases
  • HIF1A
  • ras Proteins
  • Signal Transduction
  • Cell Cycle
  • Messenger RNA
  • Protein-Serine-Threonine Kinases
  • Disease Models, Animal
  • Cell Cycle Proteins
  • Vascular Endothelial Growth Factor Receptor-2
  • Cell Survival
  • Transcription Factors
  • MicroRNAs
  • Myeloid Leukemia
  • DNA Damage
  • Signal Transducing Adaptor Proteins
  • Liver Cancer
  • Cancer Gene Expression Regulation
  • Leukaemia
  • Knockout Mice
  • Oligonucleotide Array Sequence Analysis
  • Down-Regulation
  • Gene Expression
  • Immunohistochemistry
  • Xenograft Models
  • siRNA
  • Promoter Regions
  • Neoplasm Proteins
  • Chromosome 10
  • TOR Serine-Threonine Kinases
  • Protein Binding
  • Prostate Cancer
  • U937 Cells
  • Apoptosis
  • Gene Expression Profiling
  • Breast Cancer
  • Nuclear Proteins
  • Cell Hypoxia
  • VHL
  • Cell Proliferation
  • Antineoplastic Agents
  • Phosphorylation
Tag cloud generated 14 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: DDIT4 (cancer-related)

Çelik H, Bulut G, Han J, et al.
Ezrin Inhibition Up-regulates Stress Response Gene Expression.
J Biol Chem. 2016; 291(25):13257-70 [PubMed] Article available free on PMC after 17/06/2017 Related Publications
Ezrin is a member of the ERM (ezrin/radixin/moesin) family of proteins that links cortical cytoskeleton to the plasma membrane. High expression of ezrin correlates with poor prognosis and metastasis in osteosarcoma. In this study, to uncover specific cellular responses evoked by ezrin inhibition that can be used as a specific pharmacodynamic marker(s), we profiled global gene expression in osteosarcoma cells after treatment with small molecule ezrin inhibitors, NSC305787 and NSC668394. We identified and validated several up-regulated integrated stress response genes including PTGS2, ATF3, DDIT3, DDIT4, TRIB3, and ATF4 as novel ezrin-regulated transcripts. Analysis of transcriptional response in skin and peripheral blood mononuclear cells from NSC305787-treated mice compared with a control group revealed that, among those genes, the stress gene DDIT4/REDD1 may be used as a surrogate pharmacodynamic marker of ezrin inhibitor compound activity. In addition, we validated the anti-metastatic effects of NSC305787 in reducing the incidence of lung metastasis in a genetically engineered mouse model of osteosarcoma and evaluated the pharmacokinetics of NSC305787 and NSC668394 in mice. In conclusion, our findings suggest that cytoplasmic ezrin, previously considered a dormant and inactive protein, has important functions in regulating gene expression that may result in down-regulation of stress response genes.

Barakat DJ, Mendonca J, Barberi T, et al.
C/EBPβ regulates sensitivity to bortezomib in prostate cancer cells by inducing REDD1 and autophagosome-lysosome fusion.
Cancer Lett. 2016; 375(1):152-61 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
The purpose of this study was to ascertain the mechanisms by which advanced prostate cancer cells resist bortezomib therapy. Several independent studies have shown that cells are protected from proteasome inhibition by increased autophagic activity. We investigated whether C/EBPβ, a transcription factor involved in the control of autophagic gene expression, regulates resistance to proteasome inhibition. In PC3 cells over-expressing C/EBPβ, turnover of autophagic substrates and expression of core autophagy genes were increased. Conversely, C/EBPβ knockdown suppressed autophagosome-lysosome fusion. We also found that C/EBPβ knockdown suppressed REDD1 expression to delay early autophagy, an effect rescued by exogenous REDD1. Cells with suppressed C/EBPβ levels showed delayed autophagy activation upon bortezomib treatment. Knockdown of C/EBPβ sensitized PC3 cells to bortezomib, and blockade of autophagy by chloroquine did not further increase cell death in cells expressing shRNA targeting C/EBPβ. Lastly, we observed a decreased growth of PC3 cells and xenografts with C/EBPβ knockdown and such xenografts were sensitized to bortezomib treatment. Our results demonstrate that C/EBPβ is a critical effector of autophagy via regulation of autolysosome formation and promotes resistance to proteasome inhibitor treatment by increasing autophagy.

Yun SM, Woo SH, Oh ST, et al.
Melatonin enhances arsenic trioxide-induced cell death via sustained upregulation of Redd1 expression in breast cancer cells.
Mol Cell Endocrinol. 2016; 422:64-73 [PubMed] Related Publications
Melatonin is implicated in various physiological functions, including anticancer activity. However, the mechanism(s) of its anticancer activity is not well understood. In the present study, we investigated the combined effects of melatonin and arsenic trioxide (ATO) on cell death in human breast cancer cells. Melatonin enhanced the ATO-induced apoptotic cell death via changes in the protein levels of Survivin, Bcl-2, and Bax, thus affecting cytochrome c release from the mitochondria to the cytosol. Interestingly, we found that the cell death induced by co-treatment with melatonin and ATO was mediated by sustained upregulation of Redd1, which was associated with increased production of reactive oxygen species (ROS). Combined treatment with melatonin and ATO induced the phosphorylation of JNK and p38 MAP kinase downstream from Redd1 expression. Rapamycin and S6K1 siRNA enhanced, while activation of mTORC1 by transfection with TSC2 siRNA suppressed the cell death induced by melatonin and ATO treatment. Taken together, our findings suggest that melatonin enhances ATO-induced apoptotic cell death via sustained upregulation of Redd1 expression and inhibition of mTORC1 upstream of the activation of the p38/JNK pathways in human breast cancer cells.

Chiang IT, Wang WS, Liu HC, et al.
Curcumin alters gene expression-associated DNA damage, cell cycle, cell survival and cell migration and invasion in NCI-H460 human lung cancer cells in vitro.
Oncol Rep. 2015; 34(4):1853-74 [PubMed] Related Publications
Lung cancer is the most common cause of cancer mortality and new cases are on the increase worldwide. However, the treatment of lung cancer remains unsatisfactory. Curcumin has been shown to induce cell death in many human cancer cells, including human lung cancer cells. However, the effects of curcumin on genetic mechanisms associated with these actions remain unclear. Curcumin (2 µM) was added to NCI-H460 human lung cancer cells and the cells were incubated for 24 h. Total RNA was extracted from isolated cells for cDNA synthesis, labeling, microarray hybridization and flour‑labeled cDNA hybridized on chip. Localized concentrations of fluorescent molecules were detected and quantified using Expression Console software (Affymetrix) with default RMA parameters. GeneGo software was used for the key genes involved and their possible interaction pathways. The results showed that ~170 genes were significantly upregulated and 577 genes were significantly downregulated in curcumin‑treated cells. Specifically, the up‑ and downregulated genes included CCNE2, associated with DNA damage; ID3, associated with cell survival and 146 genes with a >2- to 3-fold change including the TP53INP1 gene, associated with DNA damage; CDC6, CDCA5, TAKMIP2, CDK14, CDK5, CDCA76, CDC25A, CDC5L and SKP2, associated with cell cycle; the CARD6, ID1 and ID2 genes, associated with cell survival and the BRMS1L, associated with cell migration and invasion. Additionally, 59 downregulated genes exhibited a >4-fold change, including the DDIT3 gene, associated with DNA damage; while 97 genes had a >3- to 4-fold change including the DDIT4 gene, associated with DNA damage; the CCPG1 gene, associated with cell cycle and 321 genes with a >2- to 3-fold including the GADD45A and CGREF1 genes, associated with DNA damage; the CCPG1 gene, associated with cell cycle, the TNFRSF10B, GAS5, TSSC1 and TNFRSF11B gene, associated with cell survival and the ARHAP29 and CADM2 genes, associated with cell migration and invasion. In conclusion, gene alterations provide information regarding the cytotoxic mechanism of curcumin at the genetic level and provide additional biomarkers or targets for the treatment of human lung cancer.

Chang IC, Chiang TI, Lo C, et al.
Anemone altaica Induces Apoptosis in Human Osteosarcoma Cells.
Am J Chin Med. 2015; 43(5):1031-42 [PubMed] Related Publications
In the past decade, no significant improvement has been made in chemotherapy for osteosarcoma (OS). To develop improved agents against OS, we screened 70 species of medicinal plants and treated two human OS cell lines with different agent concentrations. We then examined cell viability using the MTT assay. Results showed that a candidate plant, particularly the rhizomes of Anemone altaica Fisch. ex C. A. Mey aqueous extract (AAE), suppressed the viability of HOS and U2OS cells in a concentration-dependent manner. Flow cytometry analysis revealed that AAE significantly increased the amount of cell shrinkage (Sub-G1 fragments) in HOS and U2OS cells. Moreover, AAE increased cytosolic cytochrome c and Bax, but decreased Bcl-2. The amount of cleaved caspase-3 and poly-(ADP-ribose) polymerase-1 (PARP-1) were significantly increased. AAE suppressed the growth of HOS and U2OS through the intrinsic apoptotic pathway. Data suggest that AAE is cytotoxic to HOS and U2OS cells and has no significant influence on human osteoblast hFOB cells. The high mRNA levels of apoptosis-related factors (PPP1R15A, SQSTM1, HSPA1B, and DDIT4) and cellular proliferation markers (SKA2 and BUB1B) were significantly altered by the AAE treatment of HOS and U2OS cells. Results show that the anticancer activity of AAE could up-regulate the expression of a cluster of genes, especially those in the apoptosis-related factor family and caspase family. Thus, AAE has great potential as a useful therapeutic drug for human OS.

Kim M, Kim T, Johnson RL, Lim DS
Transcriptional co-repressor function of the hippo pathway transducers YAP and TAZ.
Cell Rep. 2015; 11(2):270-82 [PubMed] Related Publications
YAP (yes-associated protein) and TAZ are oncogenic transcriptional co-activators downstream of the Hippo tumor-suppressor pathway. However, whether YAP and/or TAZ (YAP/TAZ) engage in transcriptional co-repression remains relatively unexplored. Here, we directly demonstrated that YAP/TAZ represses numerous target genes, including tumor-suppressor genes such as DDIT4 (DNA-damage-inducible transcript 4) and Trail (TNF-related apoptosis-inducing ligand). Mechanistically, the repressor function of YAP/TAZ requires TEAD (TEA domain) transcription factors. A YAP/TAZ-TEAD complex recruits the NuRD complex to deacetylate histones and alters nucleosome occupancy at target genes. Functionally, repression of DDIT4 and Trail by YAP/TAZ is required for mTORC1 (mechanistic target of rapamycin complex 1) activation and cell survival, respectively. Our demonstration of the transcriptional co-repressor activity of YAP/TAZ opens a new avenue for understanding the Hippo signaling pathway.

Hsia TC, Yu CC, Hsu SC, et al.
cDNA microarray analysis of the effect of cantharidin on DNA damage, cell cycle and apoptosis-associated gene expression in NCI-H460 human lung cancer cells in vitro.
Mol Med Rep. 2015; 12(1):1030-42 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
Cantharidin (CTD) induces cytotoxic effects in different types of human cancer cell; however, to date, there have been no studies on the effects of CTD on gene expression in human lung cancer cells and the potential associated signaling pathways. Therefore, the present study aimed to investigate how CTD affects the expression of key genes and functional pathways of human H460 lung cancer cells using complementary DNA microarray analysis. Human H460 lung cancer cells were cultured for 24 h in the presence or absence of 10 µM CTD; gene expression was then examined using microarray analysis. The results indicated that 8 genes were upregulated > 4-fold, 29 genes were upregulated >3-4-fold and 156 genes were upregulated >2-3-fold. In addition, 1 gene was downregulated >4 fold, 14 genes were downregulated >3-4-fold and 150 genes were downregulated >2-3 fold in H460 cells following exposure to CTD. It was found that CTD affected DNA damage genes, including DNIT3 and GADD45A, which were upregulated 2.26- and 2.60-fold, respectively, as well as DdiT4, which was downregulated 3.14-fold. In addition, the expression of genes associated with the cell cycle progression were altered, including CCND2, CDKL3 and RASA4, which were upregulated 2.72-, 2.19- and 2.72-fold, respectively; however, CDC42EP3 was downregulated 2.16-fold. Furthermore, apoptosis-associated genes were differentially expressed, including CARD6, which was upregulated 3.54-fold. In conclusion, the present study demonstrated that CTD affected the expression of genes associated with DNA damage, cell cycle progression and apoptotic cell death in human lung cancer H460 cells.

Wang S, Chen XA, Hu J, et al.
ATF4 Gene Network Mediates Cellular Response to the Anticancer PAD Inhibitor YW3-56 in Triple-Negative Breast Cancer Cells.
Mol Cancer Ther. 2015; 14(4):877-88 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
We previously reported that a pan-PAD inhibitor, YW3-56, activates p53 target genes to inhibit cancer growth. However, the p53-independent anticancer activity and molecular mechanisms of YW3-56 remain largely elusive. Here, gene expression analyses found that ATF4 target genes involved in endoplasmic reticulum (ER) stress response were activated by YW3-56. Depletion of ATF4 greatly attenuated YW3-56-mediated activation of the mTORC1 regulatory genes SESN2 and DDIT4. Using the ChIP-exo method, high-resolution genomic binding sites of ATF4 and CEBPB responsive to YW3-56 treatment were generated. In human breast cancer cells, YW3-56-mediated cell death features mitochondria depletion and autophagy perturbation. Moreover, YW3-56 treatment effectively inhibits the growth of triple-negative breast cancer xenograft tumors in nude mice. Taken together, we unveiled the anticancer mechanisms and therapeutic potentials of the pan-PAD inhibitor YW3-56.

Wang Y, Han E, Xing Q, et al.
Baicalein upregulates DDIT4 expression which mediates mTOR inhibition and growth inhibition in cancer cells.
Cancer Lett. 2015; 358(2):170-9 [PubMed] Related Publications
Baicalein is a natural flavone that exhibits anticancer properties. Using microarrays we found that DDIT4 was the highest transcript induced by baicalein in cancer cells. We confirmed in multiple cancer cell lines large, dose-related expression of DDIT4 by quantitative RT-PCR and immunoblot, which correlates with growth inhibition. Time course experiments demonstrate that DDIT4 is rapidly inducible, with high expression maintained for several days in vitro. Induction of DDIT4 expression is p53 independent based on evaluation of p53 knockout cells. Since DDIT4 is known to inhibit mTORC1 activity we confirmed that baicalein suppresses phosphorylation of mTORC1 targets. Using RNA interference we demonstrate that mTORC1 activity and growth inhibition by baicalein is attenuated by knockdown of DDIT4. We furthermore demonstrate suppression of established tumors by baicalein in a mouse model of breast cancer with increased DDIT4 expression in the tumors. Finally, we demonstrate that baicalein upregulates DDIT4 and causes mTORC1 and growth inhibition in platinum resistant cancer cells in marked contrast to platinum chemotherapy treatment. These studies demonstrate that baicalein inhibits mTORC1 through DDIT4 expression, and may be useful in cancer chemotherapy and chemoprevention.

Cao JX, Lu Y, Qi JJ, et al.
MiR-630 inhibits proliferation by targeting CDC7 kinase, but maintains the apoptotic balance by targeting multiple modulators in human lung cancer A549 cells.
Cell Death Dis. 2014; 5:e1426 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
MicroRNAome analyses have shown microRNA-630 (miR-630) to be involved in the regulation of apoptosis. However, its apoptotic role is still debated and its participation in DNA replication is unknown. Here, we demonstrate that miR-630 inhibits cell proliferation by targeting cell-cycle kinase 7 (CDC7) kinase, but maintains the apoptotic balance by targeting multiple activators of apoptosis under genotoxic stress. We identified a novel regulatory mechanism of CDC7 gene expression, in which miR-630 downregulated CDC7 expression by recognizing and binding to four binding sites in CDC7 3'-UTR. We found that miR-630 was highly expressed in A549 and NIH3T3 cells where CDC7 was downregulated, but lower in H1299, MCF7, MDA-MB-231, HeLa and 2BS cells where CDC7 was upregulated. Furthermore, the induction of miR-630 occurred commonly in a variety of human cancer and immortalized cells in response to genotoxic agents. Importantly, downregulation of CDC7 by miR-630 was associated with cisplatin (CIS)-induced inhibitory proliferation in A549 cells. Mechanistically, miR-630 exerted its inhibitory proliferation by blocking CDC7-mediated initiation of DNA synthesis and by inducing G1 arrest, but maintains apoptotic balance under CIS exposure. On the one hand, miR-630 promoted apoptosis by downregulation of CDC7; on the other hand, it reduced apoptosis by downregulating several apoptotic modulators such as PARP3, DDIT4, EP300 and EP300 downstream effector p53, thereby maintaining the apoptotic balance. Our data indicate that miR-630 has a bimodal role in the regulation of apoptosis in response to DNA damage. Our data also support the notion that a certain mRNA can be targeted by several miRNAs, and in particular an miRNA may target a set of mRNAs. These data afford a comprehensive view of microRNA-dependent control of gene expression in the regulation of apoptosis under genotoxic stress.

Thompson JW, Nagel J, Hoving S, et al.
Quantitative Lys-ϵ-Gly-Gly (diGly) proteomics coupled with inducible RNAi reveals ubiquitin-mediated proteolysis of DNA damage-inducible transcript 4 (DDIT4) by the E3 ligase HUWE1.
J Biol Chem. 2014; 289(42):28942-55 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
Targeted degradation of proteins through the ubiquitin-proteasome system (UPS) via the activities of E3 ubiquitin ligases regulates diverse cellular processes, and misregulation of these enzymes contributes to the pathogenesis of human diseases. One of the challenges facing the UPS field is to delineate the complete cohort of substrates for a particular E3 ligase. Advances in mass spectrometry and the development of antibodies recognizing the Lys-ϵ-Gly-Gly (diGly) remnant from ubiquitinated proteins following trypsinolysis have provided a tool to address this question. We implemented an inducible loss of function approach in combination with quantitative diGly proteomics to find novel substrates of HUWE1 (HECT, UBA, and WWE domain containing 1, E3 ubiquitin protein ligase), an E3 ligase implicated in cancer and intellectual disabilities. diGly proteomics results led to the identification of DNA damage-inducible transcript 4 (DDIT4) as a putative HUWE1 substrate. Cell-based assays demonstrated that HUWE1 interacts with and regulates ubiquitination and stability of DDIT4. Together these data suggest a model in which HUWE1 mediates DDIT4 proteasomal degradation. Our results demonstrate proof of concept that inducible knockdown of an E3 ligase in combination with diGly proteomics provides a potentially advantageous method for identifying novel E3 substrates that may help to identify candidates for therapeutic modulation in the UPS.

Lin CC, Chao PY, Shen CY, et al.
Novel target genes responsive to apoptotic activity by Ocimum gratissimum in human osteosarcoma cells.
Am J Chin Med. 2014; 42(3):743-67 [PubMed] Related Publications
Osteosarcoma (OS) is a type of bone cancer. Eighty percent of this tumor will metastasize to the lungs or liver, and as a result, patients generally need chemotherapy to improve survival possibility. Recently, antitumor activity has been reported in Ocimum gratissimum aqueous extract (OGE), which has been the focus of recent extensive studies on therapeutic strategies due to its antioxidant properties. We performed pharmacogenomics analyses for the effect of OGE on human osteosarcoma U2-OS and HOS cell growth. Cell viability, Western blot and flow cytometry analysis were performed before performing pharmacogenomics analyses for the effect of OGE on human osteosarcoma U2-OS and HOS cell growth, including cDNA microarray and RT-PCR assays. Cell viability assays revealed that OGE significantly and dose-dependently decreased the viability of U2-OS and HOS cells. Increases in cell shrinkage, Sub-G1 fragments and the activation of caspase 3 indicated that OGE induced cell apoptosis in U2-OS and HOS cells. There was no change in human osteoblast hFOS cells. cDNA microarray assay demonstrated that the expression of cell cycle regulators, apoptosis-related factors and cell proliferation markers were all modified by OGE treatment. RT-PCR analysis also confirmed the down-regulation of SKA2 and BUB1B, and the up-regulation of PPP1R15A, SQSTM1, HSPA1B, and DDIT4 by OGE treatment. The finding of anticancer activity in OGE and the identification of some potential target genes raise the expectation that OGE may become a useful therapeutic drug for human OS.

Wu SH, Hsiao YT, Chen JC, et al.
Bufalin alters gene expressions associated DNA damage, cell cycle, and apoptosis in human lung cancer NCI-H460 cells in vitro.
Molecules. 2014; 19(5):6047-57 [PubMed] Related Publications
Lung cancer is the leading cause of cancer related death and there is no effective treatment to date. Bufalin has been shown effective in inducing apoptosis and DNA damage in lung cancer cells. However, the genetic mechanisms underlying these actions have not been elucidated yet. Cultured NCI-H460 cells were treated with or without 2 μM of bufalin for 24 h. The total RNA was extracted from each treatment for cDNA synthesis and labeling, microarray hybridization, and then followed by flour-labeled cDNA hybridized on chip. The localized concentrations of fluorescent molecules were detected and quantitated and analyzed by Expression Console software (Affymetrix) with default RMA parameters. The key genes involved and their possible interaction pathways were mapped by GeneGo software. About 165 apoptosis-related genes were affected. CASP9 was up-regulated by 5.51 fold and THAP1 by 2.75-fold while CCAR1 was down-regulated by 2.24 fold. 107 genes related to DNA damage/repair were affected. MDC1 was down-regulated by 2.22-fold, DDIT4 by 2.52 fold while GADD45B up-regulated by 3.72 fold. 201 genes related to cell cycles were affected. CCPG1 was down-regulated by 2.11 fold and CDCA7L by 2.71 fold. Many genes about apoptosis, cell cycle regulation and DNA repair are changed significantly following bufalin treatment in NCI-H460 cells. These changes provide an in depth understanding of cytotoxic mechanism of bufalin in genetic level and also offer many potentially useful biomarkers for diagnosis and treatment of lung cancer in future.

He Y, Meng XM, Huang C, et al.
Long noncoding RNAs: Novel insights into hepatocelluar carcinoma.
Cancer Lett. 2014; 344(1):20-7 [PubMed] Related Publications
Recent advances in non-protein coding part of human genome analysis have discovered extensive transcription of large RNA transcripts that lack of coding protein function, termed long noncoding RNAs (lncRNAs). It is becoming evident that lncRNAs may be an important class of pervasive genes involved in carcinogenesis and metastasis. However, the biological and molecular mechanisms of lncRNAs in diverse diseases are not yet fully understood. Thus, it is anticipated that more efforts should be made to clarify the lncRNAs world. Moreover, accumulating studies have demonstrated that a class of lncRNAs are dysregulated in hepatocellular carcinoma(HCC) and closely related with tumorigenesis, metastasis, prognosis or diagnosis. In this review, we will briefly discuss the regulation and functional role of lncRNAs in HCC, therefore evaluating the potential of lncRNAs as prospective novel therapeutic targets in HCC.

Corominas-Faja B, Cufí S, Oliveras-Ferraros C, et al.
Nuclear reprogramming of luminal-like breast cancer cells generates Sox2-overexpressing cancer stem-like cellular states harboring transcriptional activation of the mTOR pathway.
Cell Cycle. 2013; 12(18):3109-24 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
Energy metabolism plasticity enables stemness programs during the reprogramming of somatic cells to an induced pluripotent stem cell (iPSC) state. This relationship may introduce a new era in the understanding of Warburg's theory on the metabolic origin of cancer at the level of cancer stem cells (CSCs). Here, we used Yamanaka's stem cell technology in an attempt to create stable CSC research lines in which to dissect the transcriptional control of mTOR--the master switch of cellular catabolism and anabolism--in CSC-like states. The rare colonies with iPSC-like morphology, obtained following the viral transduction of the Oct4, Sox2, Klf4, and c-Myc (OSKM) stemness factors into MCF-7 luminal-like breast cancer cells (MCF-7/Rep), demonstrated an intermediate state between cancer cells and bona fide iPSCs. MCF-7/Rep cells notably overexpressed SOX2 and stage-specific embryonic antigen (SSEA)-4 proteins; however, other stemness-related markers (OCT4, NANOG, SSEA-1, TRA-1-60, and TRA-1-81) were found at low to moderate levels. The transcriptional analyses of OSKM factors confirmed the strong but unique reactivation of the endogenous Sox2 stemness gene accompanied by the silencing of the exogenous Sox2 transgene in MCF-7/Rep cells. Some but not all MCF-7/Rep cells acquired strong alkaline phosphatase (AP) activity compared with MCF-7 parental cells. SOX2-overexpressing MCF-7/Rep cells contained drastically higher percentages of CD44(+) and ALDEFLUOR-stained ALDH(bright) cells than MCF-7 parental cells. The overlap between differentially expressed mTOR signaling-related genes in 3 different SOX2-overexpressing CSC-like cell lines revealed a notable downregulation of 3 genes, PRKAA1 (which codes for the catalytic α 1 subunit of AMPK), DDIT4/REDD1 (a stress response gene that operates as a negative regulator of mTOR), and DEPTOR (a naturally occurring endogenous inhibitor of mTOR activity). The insulin-receptor gene (INSR) was differentially upregulated in MCF-7/Rep cells. Consistent with the downregulation of AMPK expression, immunoblotting procedures confirmed upregulation of p70S6K and increased phosphorylation of mTOR in Sox2-overexpressing CSC-like cell populations. Using an in vitro model of the de novo generation of CSC-like states through the nuclear reprogramming of an established breast cancer cell line, we reveal that the transcriptional suppression of mTOR repressors is an intrinsic process occurring during the acquisition of CSC-like properties by differentiated populations of luminal-like breast cancer cells. This approach may provide a new path for obtaining information about preventing the appearance of CSCs through the modulation of the AMPK/mTOR pathway.

Slattery ML, John EM, Torres-Mejia G, et al.
Angiogenesis genes, dietary oxidative balance and breast cancer risk and progression: the Breast Cancer Health Disparities Study.
Int J Cancer. 2014; 134(3):629-44 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
Angiogenesis is essential for tumor development and progression. Genetic variation in angiogenesis-related genes may influence breast carcinogenesis. We evaluated dietary factors associated with oxidative balance, DDIT4 (one SNP), FLT1 (35 SNPs), HIF1A (four SNPs), KDR (19 SNPs), MPO (one SNP), NOS2A (15 SNPs), TEK (40 SNPs) and VEGFA (eight SNPs) and breast cancer risk among Hispanic (2,111 cases and 2,597 controls) and non-Hispanic white (1,481 cases and 1,586 controls) women in the Breast Cancer Health Disparities Study. Adaptive rank truncated product (ARTP) analysis was used to determine gene and pathway significance with breast cancer. TEK was associated with breast cancer overall (pARTP = 0.03) and with breast cancer survival (pARTP = 0.01). KDR was of borderline significance overall (pARTP = 0.07), although significantly associated with breast cancer in both low and intermediate Native American (NA) ancestry groups (pARTP = 0.02) and estrogen receptor (ER)+/progesterone receptor (PR)- tumor phenotype (pARTP = 0.008). Both VEGFA and NOS2A were associated with ER-/PR- tumor phenotype (pARTP = 0.01 and pARTP = 0.04, respectively). FLT1 was associated with breast cancer survival among those with low NA ancestry (pARTP = 0.009). With respect to diet, having a higher dietary oxidative balance score (DOBS) was significantly associated with lower breast cancer risk [odds ratio (OR) 0.74, 95% confidence interval (CI) 0.64-0.84], with the strongest associations observed for women with the highest NA ancestry (OR 0.44, 95% CI 0.30-0.65). We observed few interactions between DOBS and angiogenesis-related genes. Our data suggest that dietary factors and genetic variation in angiogenesis-related genes contribute to breast cancer carcinogenesis.

Bonzheim I, Irmler M, Klier-Richter M, et al.
Identification of C/EBPβ target genes in ALK+ anaplastic large cell lymphoma (ALCL) by gene expression profiling and chromatin immunoprecipitation.
PLoS One. 2013; 8(5):e64544 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
C/EBPβ (CCAAT enhancer binding protein) is a transcription factor that plays a crucial role in survival and transformation of ALK+ anaplastic large cell lymphoma (ALCL). The aim of this study was to identify the downstream targets of C/EBPβ responsible for ALK-mediated oncogenesis. C/EBPβ was knocked down in ALK+ ALCL cell lines with a C/EBPβ-shRNA, followed by gene expression profiling (GEP). GEP analysis revealed a reproducible signature of genes that were significantly regulated by C/EBPβ. Classification into biological categories revealed overrepresentation of genes involved in the immune response, apoptosis and cell proliferation. Transcriptional regulation by C/EBPβ was found in 6 of 11 (BCL2A1, G0S2, TRIB1, S100A9, DDX21 and DDIT4) genes investigated by chromatin immunoprecipitation. We demonstrated that BCL2A1, G0S2 and DDX21 play a crucial role in survival and proliferation of ALK+ ALCL cells. DDX21, a gene involved in rRNA biogenesis, was found differentially overexpressed in primary ALK+ ALCL cases. All three candidate genes were validated in primary ALCL cases by either immunohistochemistry or RT-qPCR. In conclusion, we identified and validated several key C/EBPβ-regulated genes with major impact on survival and cell growth in ALK+ ALCL, supporting the central role of C/EBPβ in ALK-mediated oncogenesis.

Jiang L, Yang S, Yin H, et al.
Epithelial-specific deletion of 11β-HSD2 hinders Apcmin/+ mouse tumorigenesis.
Mol Cancer Res. 2013; 11(9):1040-50 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
UNLABELLED: Cyclooxygenase-2 (COX-2)-derived prostaglandin E2 (PGE2) promotes colorectal tumorigenesis. Glucocorticoids are endogenous and potent COX-2 inhibitors, and their local actions are downregulated by 11β-hydroxysteroid dehydrogenase type II (11β-HSD2)-mediated metabolism. Previously, it was reported that 11β-HSD2 is increased in human colonic and Apc(min/+) mouse intestinal adenomas and correlated with increased COX-2, and 11β-HSD2 inhibition suppressed the COX-2 pathway and decreased tumorigenesis. Because 11β-HSD2 is expressed in Apc(min/+) mouse intestinal adenoma stromal and epithelial cells, Apc(min/+) mice were generated with selective deletion of 11β-HSD2 in intestinal epithelial cells (Vil-Cre-HSD2(-/-) Apc(min/+)). Deletion of 11β-HSD2 in intestinal epithelia led to marked inhibition of Apc(min/+) mouse intestinal tumorigenesis. Immunostaining indicated decreased 11β-HSD2 and COX-2 expression in adenoma epithelia, whereas stromal COX-2 expression was intact in Vil-Cre-HSD2(-/-) Apc(min/+) mice. In Vil-Cre-HSD2(-/-) Apc(min/+) mouse intestinal adenomas, both p53 and p21 mRNA and protein were increased, with a concomitant decrease in pRb, indicating glucocorticoid-mediated G1-arrest. Further study revealed that REDD1 (regulated in development and DNA damage responses 1), a novel stress-induced gene that inhibits mTOR signaling, was increased, whereas the mTOR signaling pathway was inhibited. Therefore, in Vil-Cre-HSD2(-/-) Apc(min/+) mice, epithelial cell 11β-HSD2 deficiency leads to inhibition of adenoma initiation and growth by attenuation of COX-2 expression, increased cell-cycle arrest, and inhibition of mTOR signaling as a result of increased tumor intracellular active glucocorticoids.
IMPLICATIONS: Inhibition of 11β-HSD2 may represent a novel approach for colorectal cancer chemoprevention by increasing tumor glucocorticoid activity, which in turn inhibits tumor growth by multiple pathways.

Liu Y, Gao F, Jiang H, et al.
Induction of DNA damage and ATF3 by retigeric acid B, a novel topoisomerase II inhibitor, promotes apoptosis in prostate cancer cells.
Cancer Lett. 2013; 337(1):66-76 [PubMed] Related Publications
Retigeric acid B (RB) has been reported to exhibit its anti-tumor activity in vitro and in vivo. Here, we found that RB significantly inhibited activity of topoisomerase IIα (Topo IIα), leading to remarkable DNA damage in prostate cancer (PCa) cells as evidenced by a strong induction of γH2AX and DNA fragmentation. Activation of ATM and ATR sequentially led to induction of phospho-Chk1/2 and phospho-Cdc25 in response to RB. Blockade of ATM/ATR signaling resulted in the attenuation of RB-induced γH2AX, and partially rescued RB-mediated cell death. RB treatment also resulted in inactivation of DNA repair proteins such as phospho-BRCA1, impairment of HR, and NHEJ repair as indicated by DNA end-joining assays. Meanwhile, a stress-responsive gene activating transcription factor 3 (ATF3) was noted for its predominant expression in response to RB-induced DNA damage. Knockdown of ATF3 inhibited the RB-induced expression changes of cell cycle- and apoptosis-related genes such as DR5, DDIT4, CDC25A, GADD45A, and partially blocked RB-mediated inhibition on cell proliferation and induction of apoptosis, suggesting the crucial involvement of ATF3 in this event. Microarray data displayed that RB caused changes of genes required for damaged-DNA binding and repair, as well as ATF3 and its target genes. Our data firstly demonstrated that RB was a novel DNA Topo II inhibitor and triggered cell death by inducing DNA damage and stress-response, suggesting a promising anticancer agent.

Huang G, Ho B, Conroy J, et al.
The microarray gene profiling analysis of glioblastoma cancer cells reveals genes affected by FAK inhibitor Y15 and combination of Y15 and temozolomide.
Anticancer Agents Med Chem. 2014; 14(1):9-17 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
Focal adhesion is known to be highly expressed and activated in glioma cells. Recently, we demonstrated that FAK autophosphorylation inhibitor, Y15 significantly decreased tumor growth of DBTRG and U87 cells, especially in combination with temozolomide. In the present report, we performed gene expression analysis in these cells to reveal genes affected by Y15, temozolomide and combination of Y15 and temozolomide. We tested the effect of Y15 on gene expression by Illumina Human HT12v4 microarray assay and detected 8087 and 6555 genes, which were significantly either up- or down-regulated by Y15-treatment in DBTRG and U87 cells, respectively (p<0.05). Moreover, DBTRG and U87 cells treated with Y15 changed expression of 1332 and 462 genes more than 1.5 fold, p<0.05, respectively and had 237 common genes affected by Y15. The common genes up-regulated by Y15 included GADD45A, HSPA6 (heat-shock 70); DUSP1, DUSP 5 (dual-phosphatase 5); CDKN1A (p21) and common down-regulated genes included kinesins, such as KIF11, 14, 20A, 20B; topoisomerase II, TOP2A; cyclin F; cell cycle protein: BUB1; PARP1, POLA1. In addition, we detected genes affected by temozolomide and by combination of Y15 and temozolomide treatment in U87 cells. Among genes up-regulated by Y15 and temozolomide more significantly than by each agent alone were: COX7B; interferon, gamma-inducible transcript: IFI16; DDIT4; GADD45G and down-regulated: KIF3A, AKT1; ABL; JAK1, GLI3 and ALDH1A3. Thus, microarray gene expression analysis can be effective in establishing genes affected in response to FAK inhibitor alone and in response to combination of Y15 with temozolomide that is important for glioblastoma therapy.

Caporali S, Alvino E, Levati L, et al.
Down-regulation of the PTTG1 proto-oncogene contributes to the melanoma suppressive effects of the cyclin-dependent kinase inhibitor PHA-848125.
Biochem Pharmacol. 2012; 84(5):598-611 [PubMed] Related Publications
We previously demonstrated that PHA-848125, a cyclin-dependent kinase inhibitor presently under Phase II clinical investigation, impairs melanoma cell growth. In this study, gene expression profiling showed that PHA-848125 significantly modulated the expression of 128 genes, predominantly involved in cell cycle control, in the highly drug-sensitive GL-Mel (p53 wild-type) melanoma cells. Up-regulation of 4 selected genes (PDCD4, SESN2, DDIT4, DEPDC6), and down-regulation of 6 selected genes (PTTG1, CDC25A, AURKA, AURKB, PLK1, BIRC5) was confirmed at protein levels. The same protein analysis performed in PHA-848125-treated M10 melanoma cells - p53 mutated and less sensitive to the drug than GL-Mel cells - revealed no DEPDC6 expression and no changes of PTTG1, PDCD4 and BIRC5 levels. Upon PHA-848125 treatment, a marked PTTG1 down-modulation was also observed in A375 cells (p53 wild-type) but not in CN-Mel cells (p53 mutated). PTTG1 silencing significantly inhibited melanoma cell proliferation and induced senescence, with effects less pronounced in p53 mutated cells. PTTG1 silencing increased PHA-848125 sensitivity of p53 mutated cells but not that of A375 or GL-Mel cells. Accordingly, in M10 but not in A375 cells a higher level of senescence was detected in PHA-848125-treated/PTTG1-silenced cells with respect to PHA-848125-treated controls. In A375 and GL-Mel cells, TP53 silencing attenuated PHA-848125-induced down-modulation of PTTG1 and decreased cell sensitivity to the drug. These findings indicate that PHA-848125-induced down-regulation of PTTG1 depends, at least in part, on p53 function and contributes to the antiproliferative activity of the drug. Our study provides further molecular insight into the antitumor mechanism of PHA-848125.

Kucejova B, Peña-Llopis S, Yamasaki T, et al.
Interplay between pVHL and mTORC1 pathways in clear-cell renal cell carcinoma.
Mol Cancer Res. 2011; 9(9):1255-65 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
mTOR complex 1 (mTORC1) is implicated in cell growth control and is extensively regulated. We previously reported that in response to hypoxia, mTORC1 is inhibited by the protein regulated in development and DNA damage response 1 (REDD1). REDD1 is upregulated by hypoxia-inducible factor (HIF)-1, and forced REDD1 expression is sufficient to inhibit mTORC1. REDD1-induced mTORC1 inhibition is dependent on a protein complex formed by the tuberous sclerosis complex (TSC)1 and 2 (TSC2) proteins. In clear-cell renal cell carcinoma (ccRCC), the von Hippel-Lindau (VHL) gene is frequently inactivated leading to constitutive activation of HIF-2 and/or HIF-1, which may be expected to upregulate REDD1 and inhibit mTORC1. However, mTORC1 is frequently activated in ccRCC, and mTORC1 inhibitors are effective against this tumor type; a paradox herein examined. REDD1 was upregulated in VHL-deficient ccRCC by in silico microarray analyses, as well as by quantitative real-time PCR, Western blot, and immunohistochemistry. Vhl disruption in a mouse model was sufficient to induce Redd1. Using ccRCC-derived cell lines, we show that REDD1 upregulation in tumors is VHL dependent and that both HIF-1 and HIF-2 are, in a cell-type-dependent manner, recruited to, and essential for, REDD1 induction. Interestingly, whereas mTORC1 is responsive to REDD1 in some tumors, strategies have evolved in others, such as mutations disrupting TSC1, to subvert mTORC1 inhibition by REDD1. Sequencing analyses of 77 ccRCCs for mutations in TSC1, TSC2, and REDD1, using PTEN as a reference, implicate the TSC1 gene, and possibly REDD1, as tumor suppressors in sporadic ccRCC. Understanding how ccRCCs become refractory to REDD1-induced mTORC1 inhibition should shed light into the development of ccRCC and may aid in patient selection for molecular-targeted therapies.

Kim YS, Jin HO, Seo SK, et al.
Sorafenib induces apoptotic cell death in human non-small cell lung cancer cells by down-regulating mammalian target of rapamycin (mTOR)-dependent survivin expression.
Biochem Pharmacol. 2011; 82(3):216-26 [PubMed] Related Publications
Sorafenib, a multikinase inhibitor, is emerging as a promising targeted agent that may possess antitumor activity against a broad range of cancers. The mechanism by which sorafenib induces lung cancer cell death and apoptosis, however, is not understood. In the present study, we provide evidence that sorafenib acts through inhibition of mammalian target of rapamycin (mTOR) to down-regulate survivin and promote apoptotic cell death in human non-small cell lung cancer (NSCLC) cells. Sorafenib induced ATF4-mediated Redd1 expression, leading to mTOR inhibition-the upstream signal for down-regulation of survivin. Overexpression of survivin reduced sorafenib-induced apoptosis, whereas silencing survivin using small interfering RNA (siRNA) enhanced it, supporting the interpretation that down-regulation of survivin is involved in sorafenib-induced cell death in human NSCLC cells. Furthermore, sorafenib abolished the induction of survivin that normally accompanies IGF-1-stimulated mTOR activation. We further found that Redd1-induced mTOR down-regulation and ATF4/CHOP-induced expression of the TRAIL receptor DR5 associated with sorafenib treatment helped sensitize cells to TRAIL-induced apoptosis. Our study suggests that sorafenib mediates apoptotic cell death in human NSCLC cells through Redd1-induced inhibition of mTOR and subsequent down-regulation of survivin, events that are associated with sensitization to TRAIL-induced apoptotic cell death.

Koo JS, Kim H
Hypoxia-related protein expression and its clinicopathologic implication in carcinoma of unknown primary.
Tumour Biol. 2011; 32(5):893-904 [PubMed] Related Publications
Carcinoma of unknown primary (CUP) is a heterogeneous entity with different clinical and histological features. The aim of this study was to investigate the clinicopathological features and expression of proteins associated with carcinogenesis and tumor environment in different histological subtypes of CUP. Sixty-nine cases of CUP were subjected to immunohistochemistry for EGFR, phospho-EGFR, HER-2, phospho-HER-2, p53, ERCC1, RRM1, REDD1, HIF1α, COX-2, GLUT-1, 14-3-3σ, Phospho-mTOR, Phospho-S6, AMPKα1, Phospho-Akt, PDGF-β receptor, and caveolin-1, and fluorescence in situ hybridization for HER-2 gene amplification. Fourteen (20.3%) cases were poorly differentiated carcinoma, 24 (34.8%) were adenocarcinoma (AD), 17 (24.6%) were squamous cell carcinoma (SC), and 14 (20.3%) were undifferentiated carcinoma (UD). AD were mostly carcinomatosis type, while SC and UD were mostly nodal type (p < 0.001). SC showed more frequent EGFR overexpression (p < 0.001) and Glut-1 (p = 0.001). AD (p = 0.001) and carcinomatosis (p < 0.001) types showed shorter overall survival. SCs expressing Glut-1, HIF1α, and COX2 showed a poor prognosis (p = 0.048, 0.029, and 0.042, respectively). CUP shows various clinicopathological features according to the histological subtypes. SC is mainly associated with nodal metastasis in the head and neck, and frequent EGFR overexpression and Glut-1 expression. Glut-1, HIF1α, and COX2 expression in SC is associated with a poor prognosis.

Koo JS, Jung W
Alteration of REDD1-mediated mammalian target of rapamycin pathway and hypoxia-inducible factor-1α regulation in human breast cancer.
Pathobiology. 2010; 77(6):289-300 [PubMed] Related Publications
OBJECTIVE: The purpose of this study is to investigate REDD1-(regulated in development and DNA damage response 1) mediated regulation of the mammalian target of rapamycin (mTOR) pathway in breast cancer.
METHODS: A tissue microarray included samples from 224 patients with breast cancer, and 30 patients with papilloma were used as a control group. An immunohistochemistry (IHC) including estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), epithelial growth factor receptor, cytokeratin 5/6, glucose transporter 1 (Glut-1), hypoxia-inducible factor (HIF)-1α, REDD1, AMPK (5'-adenosine-monophosphate-activated protein kinase) α(1), 14-3-3σ, phosphatase and tensin homolog, phospho-Akt, phospho-mTOR, phospho-S6, and Ki-67 was conducted. The phenotypic classification of breast cancer was performed based on the results of the IHC for ER, PR and HER2: luminal A, luminal B, HER2 overexpression and triple-negative breast cancer (TNBC).
RESULTS: Glut-1 and HIF-1α were more highly expressed in TNBC, the HER2 overexpression type and papilloma than in the luminal A and B phenotypes (p = 0.000). REDD1 expression was higher in papilloma than in breast cancer (p = 0.000), but no difference was found among the 4 breast cancer phenotypes (p = 0.307).
CONCLUSION: In the HER2 overexpression type and TNBC, tumor cell proliferation and survival in the hypoxic tumor environment could possibly be due to disinhibition of the mTOR pathway and HIF-1α stabilization by downregulation of REDD1.

Hwang-Verslues WW, Chang PH, Wei PC, et al.
miR-495 is upregulated by E12/E47 in breast cancer stem cells, and promotes oncogenesis and hypoxia resistance via downregulation of E-cadherin and REDD1.
Oncogene. 2011; 30(21):2463-74 [PubMed] Related Publications
MicroRNAs (miRNAs) are involved in tumorigenecity by regulating specific oncogenes and tumor suppressor genes, and their roles in breast cancer stem cells (BCSCs) are becoming apparent. Distinct from the CD44(+)/CD24(-/low) sub-population, we have isolated a novel PROCR(+)/ESA(+) BCSC sub-population. To explore miRNA-regulatory mechanisms in this sub-population, we performed miRNA expression profiling and found miR-495 as the most highly upegulated miRNA in PROCR(+)/ESA(+) cells. Coincidently, high upregulation of miR-495 was also found in CD44(+)/CD24(-/low) BCSCs, reflecting its potential importance in maintaining common BCSC properties. Ectopic expression of miR-495 in breast cancer cells promoted their colony formation in vitro and tumorigenesis in mice. miR-495 directly suppressed E-cadherin expression to promote cell invasion and inhibited REDD1 expression to enhance cell proliferation in hypoxia through post-transcriptional mechanism. miR-495 expression was directly modulated by transcription factor E12/E47, which itself is highly expressed in BCSCs. These findings reveal a novel regulatory pathway centered on miR-495 that contributes to BCSC properties and hypoxia resistance.

Lisse TS, Liu T, Irmler M, et al.
Gene targeting by the vitamin D response element binding protein reveals a role for vitamin D in osteoblast mTOR signaling.
FASEB J. 2011; 25(3):937-47 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
Transcriptional regulation by hormonal 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] involves occupancy of vitamin D response elements (VDREs) by the VDRE binding protein (VDRE-BP) or 1,25(OH)(2)D(3)-bound vitamin D receptor (VDR). This relationship is disrupted by elevated VDRE-BP, causing a form of hereditary vitamin D-resistant rickets (HVDRR). DNA array analysis showed that of 114 genes regulated by 1,25(OH)(2)D(3) in control cells, almost all (113) were rendered insensitive to the hormone in VDRE-BP-overexpressing HVDRR cells. Among these was the gene for DNA-damage-inducible transcript 4 (DDIT4), an inhibitor of mammalian target of rapamycin (mTOR) signaling. Chromatin immunoprecipitation PCR using 1,25(OH)(2)D(3)-treated osteoblasts confirmed that VDR and VDRE-BP compete for binding to the DDIT4 gene promoter. Expression of DDIT4 mRNA in these cells was induced (1.6-6 fold) by 1,25(OH)(2)D(3) (10-100 nM), and Western blot and flow cytometry analysis showed that this response involved suppression of phosphorylated S6K1(T389) (a downstream target of mTOR) similar to rapamycin treatment. siRNA knockdown of DDIT4 completely abrogated antiproliferative responses to 1,25(OH)(2)D(3), whereas overexpression of VDRE-BP exerted a dominant-negative effect on transcription of 1,25(OH)(2)D(3)-target genes. DDIT4, an inhibitor of mTOR signaling, is a direct target for 1,25(OH)(2)D(3) and VDRE-BP, and functions to suppress cell proliferation in response to vitamin D.

Zemskova M, Lilly MB, Lin YW, et al.
p53-dependent induction of prostate cancer cell senescence by the PIM1 protein kinase.
Mol Cancer Res. 2010; 8(8):1126-41 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
The PIM family of serine threonine protein kinases plays an important role in regulating both the growth and transformation of malignant cells. However, in a cell line-dependent manner, overexpression of PIM1 can inhibit cell and tumor growth. In 22Rv1 human prostate cells, but not in Du145 or RWPE-2, PIM1 overexpression was associated with marked increases in cellular senescence, as shown by changes in the levels of beta-galactosidase (SA-beta-Gal), p21, interleukin (IL)-6 and IL-8 mRNA and protein. During early cell passages, PIM1 induced cellular polyploidy. As the passage number increased, markers of DNA damage, including the level of gammaH2AX and CHK2 phosphorylation, were seen. Coincident with these DNA damage markers, the level of p53 protein and genes transcriptionally activated by p53, such as p21, TP53INP1, and DDIT4, increased. In these 22Rv1 cells, the induction of p53 protein was associated not only with senescence but also with a significant level of apoptosis. The importance of the p53 pathway to PIM1-driven cellular senescence was further shown by the observation that expression of dominant-negative p53 or shRNA targeting p21 blocked the PIM1-induced changes in the DNA damage response and increases in SA-beta-Gal activity. Likewise, in a subcutaneous tumor model, PIM1-induced senescence was rescued when the p53-p21 pathways are inactivated. Based on these results, PIM1 will have its most profound effects on tumorigenesis in situations where the senescence response is inactivated.

Henze AT, Acker T
Feedback regulators of hypoxia-inducible factors and their role in cancer biology.
Cell Cycle. 2010; 9(14):2749-63 [PubMed] Related Publications
Malignant tumors are characterized by regions of low oxygen concentration (hypoxia). The hypoxic tumor microenvironment contributes to tumor progression by activating a set of adaptive responses via the key transcriptional regulators HIF-1alpha and HIF-2alpha. These factors have been traditionally linked to an aggressive tumor phenotype by promoting processes essential for tumor growth, such as angiogenesis, glycolysis, metastasis and invasion, as well as differentiation and self renewal. Notably, the complex HIF pathway also initiates anti-tumorigenic mechanisms that lead to cell cycle arrest or cell death, indicating the need for a stringent control of the extent and the direction of the hypoxia response. The importance of this control for tumor cell survival is illustrated by the intricate regulation of HIF activity at the mRNA, protein and epigenetic level by a complex network of positive and negative feedback regulators. We propose that these feedback regulators help to flexibly adjust and adapt HIF activated responses to the fluctuating oxygen concentrations within tumors during acute and chronic hypoxia and to curtail the tumor-suppressing components of the HIF pathway. Moreover, feedback regulation of HIF induces a switch from HIF-1alpha to HIF-2alpha driven responses under chronic hypoxia which may have essential functions in the regulation of tumor cell differentiation and tumor stem cell maintenance. Given their central role in cancer biology, HIF feedback regulators may represent an attractive and novel anti-tumor therapy target to overcome cell death resistance in tumors.

Horak P, Crawford AR, Vadysirisack DD, et al.
Negative feedback control of HIF-1 through REDD1-regulated ROS suppresses tumorigenesis.
Proc Natl Acad Sci U S A. 2010; 107(10):4675-80 [PubMed] Article available free on PMC after 28/05/2017 Related Publications
The HIF family of hypoxia-inducible transcription factors are key mediators of the physiologic response to hypoxia, whose dysregulation promotes tumorigenesis. One important HIF-1 effector is the REDD1 protein, which is induced by HIF-1 and which functions as an essential regulator of TOR complex 1 (TORC1) activity in Drosophila and mammalian cells. Here we demonstrate a negative feedback loop for regulation of HIF-1 by REDD1, which plays a key role in tumor suppression. Genetic loss of REDD1 dramatically increases HIF-1 levels and HIF-regulated target gene expression in vitro and confers tumorigenicity in vivo. Increased HIF-1 in REDD1(-/-) cells induces a shift to glycolytic metabolism and provides a growth advantage under hypoxic conditions, and HIF-1 knockdown abrogates this advantage and suppresses tumorigenesis. Surprisingly, however, HIF-1 up-regulation in REDD1(-/-) cells is largely independent of mTORC1 activity. Instead, loss of REDD1 induces HIF-1 stabilization and tumorigenesis through a reactive oxygen species (ROS) -dependent mechanism. REDD1(-/-) cells demonstrate a substantial elevation of mitochondrial ROS, and antioxidant treatment is sufficient to normalize HIF-1 levels and inhibit REDD1-dependent tumor formation. REDD1 likely functions as a direct regulator of mitochondrial metabolism, as endogenous REDD1 localizes to the mitochondria, and this localization is required for REDD1 to reduce ROS production. Finally, human primary breast cancers that have silenced REDD1 exhibit evidence of HIF activation. Together, these findings uncover a specific genetic mechanism for HIF induction through loss of REDD1. Furthermore, they define REDD1 as a key metabolic regulator that suppresses tumorigenesis through distinct effects on mTORC1 activity and mitochondrial function.

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