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Increased expression of the dsRNA-activated protein kinase PKR in breast cancer promotes sensitivity to doxorubicin. PLoS One 2012; 7:e46040. [PMID: 23029376 PMCID: PMC3454339 DOI: 10.1371/journal.pone.0046040] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 08/28/2012] [Indexed: 11/19/2022] Open
Abstract
It has been reported that the expression and activity of the interferon-inducible, dsRNA-dependent protein kinase, PKR, is increased in mammary carcinoma cell lines and primary tumor samples. To extend these findings and determine how PKR signaling may affect breast cancer cell sensitivity to chemotherapy, we measured PKR expression by immunohistochemical staining of 538 cases of primary breast cancer and normal tissues. Significantly, PKR expression was elevated in ductal, lobular and squamous cell carcinomas or lymph node metastases but not in either benign tumor specimens or cases of inflammation compared to normal tissues. Furthermore, PKR expression was increased in precancerous stages of mammary cell hyperplasia and dysplasia compared to normal tissues, indicating that PKR expression may be upregulated by the process of tumorigenesis. To test the function of PKR in breast cancer, we generated MCF7, T-47D and MDA-MB-231 breast cancer cell lines with significantly reduced PKR expression by siRNA knockdown. Importantly, while knockdown of PKR expression had no effect on cell proliferation under normal growth conditions, MCF7, T-47D or MDA-MB-231 cells with reduced PKR expression or treated with a small molecule PKR inhibitor were significantly less sensitive to doxorubicin or H2O2-induced toxicity compared to control cells. In addition, the rate of eIF2α phosphorylation following treatment with doxorubicin was delayed in breast cancer cell lines with decreased PKR expression. Significantly, treatment of breast cancer lines with reduced PKR expression with either interferon-α, which increases PKR expression, or salubrinal, which increases eIF2α phosphorylation, restored doxorubicin sensitivity to normal levels. Taken together these results indicate that increased PKR expression in primary breast cancer tissues may serve as a biomarker for response to doxorubicin-containing chemotherapy and that future therapeutic approaches to promote PKR expression/activation and eIF2α phosphorylation may be beneficial for the treatment of breast cancer.
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Pindel A, Sadler A. The Role of Protein Kinase R in the Interferon Response. J Interferon Cytokine Res 2011; 31:59-70. [DOI: 10.1089/jir.2010.0099] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- Agnieszka Pindel
- Centre for Cancer Research, Monash Institute of Medical Research, Monash University, Melbourne, Australia
| | - Anthony Sadler
- Centre for Cancer Research, Monash Institute of Medical Research, Monash University, Melbourne, Australia
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3
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Blalock WL, Bavelloni A, Piazzi M, Faenza I, Cocco L. A role for PKR in hematologic malignancies. J Cell Physiol 2010; 223:572-91. [PMID: 20232306 DOI: 10.1002/jcp.22092] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The double-stranded RNA-dependent kinase PKR has been described for many years as strictly a pro-apoptotic kinase. Recent data suggest that the main purpose of this kinase is damage control and repair following stress and, if all else fails, apoptosis. Aberrant activation of PKR has been reported in numerous neurodegenerative diseases and cancer. Although a subset of myelodysplastic syndromes (MDS) and chronic lymphocytic leukemia contain low levels of PKR expression and activity, elevated PKR activity and/or expression have been detected in a wide range of hematologic malignancies, from bone marrow failure disorders to acute leukemia. With the recent findings that cancers containing elevated PKR activity are highly sensitive to PKR inhibition, we explore the role of PKR in hematologic malignancies, signal transduction pathways affected by PKR, and how PKR may contribute to leukemic transformation.
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Affiliation(s)
- William L Blalock
- Department of Human Anatomical Sciences, University of Bologna, Bologna, Italy
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Yamada K, Nakatsu Y, Onogi A, Takasuga A, Sugimoto Y, Ueda J, Watanabe T. Structural and Functional Analysis of the BovineMx1Promoter. J Interferon Cytokine Res 2009; 29:217-26. [DOI: 10.1089/jir.2008.0069] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Kohji Yamada
- Laboratory of Animal Breeding and Reproduction, Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
| | - Yuichiro Nakatsu
- Laboratory of Animal Breeding and Reproduction, Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
| | - Akio Onogi
- Laboratory of Animal Breeding and Reproduction, Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
| | - Akiko Takasuga
- Shirakawa Institute of Animal Genetics, Odakura, Nishigo, Fukushima, Japan
| | - Yoshikazu Sugimoto
- Shirakawa Institute of Animal Genetics, Odakura, Nishigo, Fukushima, Japan
| | - Junji Ueda
- Institute of Dairy Science, Rakuno Gakuen University, Ebetsu, Japan
| | - Tomomasa Watanabe
- Laboratory of Animal Breeding and Reproduction, Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
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Toth AM, Zhang P, Das S, George CX, Samuel CE. Interferon action and the double-stranded RNA-dependent enzymes ADAR1 adenosine deaminase and PKR protein kinase. ACTA ACUST UNITED AC 2007; 81:369-434. [PMID: 16891177 DOI: 10.1016/s0079-6603(06)81010-x] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Ann M Toth
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, California 93106, USA
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Fasciano S, Kaufman A, Patel RC. Expression of PACT is regulated by Sp1 transcription factor. Gene 2006; 388:74-82. [PMID: 17125937 PMCID: PMC1855191 DOI: 10.1016/j.gene.2006.10.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2006] [Revised: 10/03/2006] [Accepted: 10/04/2006] [Indexed: 11/15/2022]
Abstract
PACT is a stress-modulated, cellular activator of interferon (IFN)-induced double-stranded (ds) RNA-activated protein kinase (PKR) and is an important regulator of PKR-dependent signaling pathways. The research presented here is aimed at understanding the regulation of PACT expression in mammalian cells. PACT is expressed ubiquitously in different cell types at varying abundance. We have characterized the sequence elements in PACT promoter region that are required for its expression. Using deletion analysis of the promoter we have identified the minimal basal promoter of PACT to be within 101 nucleotides upstream of its transcription start site. Further mutational analyses within this region, followed by electrophoretic mobility shift analyses (EMSAs) and chromatin immunoprecipitation (ChiP) analysis have shown that Specificity protein 1 (Sp1) is the major transcription factor responsible for PACT promoter activity.
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Affiliation(s)
- Stephen Fasciano
- Department of Biological Sciences, University of South Carolina, 700 Sumter Street, Columbia, SC 29208, United States
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Kårehed K, Dimberg A, Dahl S, Nilsson K, Oberg F. IFN-gamma-induced upregulation of Fcgamma-receptor-I during activation of monocytic cells requires the PKR and NFkappaB pathways. Mol Immunol 2006; 44:615-24. [PMID: 16516295 DOI: 10.1016/j.molimm.2006.01.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Revised: 01/19/2006] [Accepted: 01/21/2006] [Indexed: 01/22/2023]
Abstract
Interferon (IFN)-gamma is a potent activator of macrophages, increasing the cells capacity to perform specific functions during inflammation and immune response. In this report we use IFN-gamma-induced upregulation of the high affinity receptor for IgG (FcgammaRI/CD64) in the human monocytic cell line U-937 as a model for monocytic activation. We show that upregulation of FcgammaRI is dependent on signals mediated by the dsRNA-dependent kinase PKR, and the transcription factor NFkappaB. Silencing of PKR expression by siRNA or inhibition of PKR by 2-aminopurine (2-AP) potently blocks the IFN-gamma-induced transcriptional activation of the FcgammaRI promoter. We find that the serine 727 phosphorylation of Stat1, required for full IFN-gamma-induced FcgammaRI promoter activity, is dependent on PKR. We further show that IFN-gamma induction of FcgammaRI upregulation is dependent on the NFkappaB pathway, as evidenced by inhibition of NFkappaB using a phosphorylation defective IkappaBalpha (S32A/S36A) mutant, or inhibiting the IkappaB-kinase (IKK) by treatment with BMS345541. Our results suggest that IFN-gamma-induced increase of FcgammaRI expression requires the integration of two signalling events: PKR-dependent Stat1 serine 727 phosphorylation, and activation of NFkappaB.
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Affiliation(s)
- Karin Kårehed
- Department of Genetics and Pathology, Rudbeck Laboratory, Uppsala University, SE-751 85 Uppsala, Sweden
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Asano A, Kon Y, Agui T. The mRNA regulation of porcine double-stranded RNA-activated protein kinase gene. J Vet Med Sci 2005; 66:1523-8. [PMID: 15644602 DOI: 10.1292/jvms.66.1523] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The double-stranded RNA (dsRNA)-activated protein kinase (PKR), which is one of the products of interferon (IFN)-stimulated genes, participates in the biological actions of IFN such as antiviral effects and immune response. In the present study, we identified the primary structure of porcine PKR proteins by cDNA cloning. Porcine PKR protein consisted of 537 amino acids and had two dsRNA-binding domains similarly existing in PKR proteins of other species. The treatment with IFN-alpha induced the expression of PKR 3.9-fold in a porcine kidney cell line, LLC-PK1. The same results were obtained when the cells were treated with poly(I).poly(C), but treatment with either IFN-gamma or LPS did not induce this gene in LLC-PK1 cells. These results suggest similarity of the regulatory mechanisms in the PKR gene among mammalian species.
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Affiliation(s)
- Atsushi Asano
- Laboratory of Experimental Animal Science, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
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Liu LG, Tanaka H, Ito K, Ito T, Sultana TA, Kyo T, Kimura A. Absence of gene mutation in TRAIL receptor 1 (TRAIL-R1) and TRAIL receptor 2 (TRAIL-R2) in chronic myelogenous leukemia and myelodysplastic syndrome, and analysis of mRNA Expressions of TRAIL and TRAIL-related genes in chronic myelogenous leukemia. Acta Haematol 2005; 113:113-23. [PMID: 15802890 DOI: 10.1159/000083449] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2004] [Accepted: 05/26/2004] [Indexed: 11/19/2022]
Abstract
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an interferon (IFN)-induced molecule with apoptotic activity. We examined gene mutations in the death domains of TRAIL receptor 1 (TRAIL-R1) and TRAIL receptor 2 (TRAIL-R2), and in the TRAIL gene promoter in 46 chronic myelogenous leukemia (CML) patients. In 23 of the 46 patients, all the coding regions of TRAIL-R2 were also examined. However, no mutation or loss of heterozygosity was found. Furthermore, no mutation in the death domains of TRAIL-R1 and TRAIL-R2 genes, which causes amino acid change, was found in 18 myelodysplastic syndrome (MDS) patients. Ribonuclease protection assay (RPA) and real-time quantitative polymerase chain reaction using polymorphonuclear neutrophils of five new CML patients showed that the TRAIL mRNA expression was very low before in vitro IFN-alpha stimulation and markedly upregulated after IFN-alpha stimulation. FAS mRNA was also upregulated with IFN-alpha stimulation but the fold induction was far lower than that of TRAIL mRNA. In addition, RPA revealed that the ratio of (TRAIL-R1 plus TRAIL-R2) to TRAIL-R3 was also increased after IFN-alpha stimulation. Taken together, gene mutations of TRAIL-R1, TRAIL-R2 are infrequent in patients with CML and MDS. And so is the TRAIL promoter for CML. These mutations seem unrelated to tumorigenesis, disease progression, and response to IFN-alpha therapy in CML. A markedly high induction of TRAIL mRNA by IFN-alpha may have some relevance to IFN-alpha action in CML patients.
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MESH Headings
- Amino Acid Substitution/genetics
- Apoptosis Regulatory Proteins
- Female
- Gene Expression Regulation, Leukemic/drug effects
- Gene Expression Regulation, Leukemic/genetics
- Humans
- Immunologic Factors/pharmacology
- Immunologic Factors/therapeutic use
- Interferon-alpha/pharmacology
- Interferon-alpha/therapeutic use
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/drug therapy
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics
- Loss of Heterozygosity/genetics
- Male
- Membrane Glycoproteins/genetics
- Middle Aged
- Myelodysplastic Syndromes/drug therapy
- Myelodysplastic Syndromes/genetics
- Open Reading Frames/genetics
- Promoter Regions, Genetic/genetics
- Protein Structure, Tertiary/genetics
- RNA, Messenger/genetics
- Receptors, TNF-Related Apoptosis-Inducing Ligand
- Receptors, Tumor Necrosis Factor/genetics
- TNF-Related Apoptosis-Inducing Ligand
- Tumor Cells, Cultured
- Tumor Necrosis Factor-alpha/genetics
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Affiliation(s)
- Li-Gen Liu
- Department of Hematology and Oncology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi, Hiroshima, Japan
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Abstract
The is a double-stranded RNA-activated protein kinase (PKR) has been largely investigated for its key role in viral host defense. Although best characterized by its function in mediating the antiviral and antiproliferative effects of interferon (IFN), PKR is also implicated in transcriptional regulation, cell differentiation, signal transduction, and tumor suppression. However, recent findings identifying PKR as an important effector of apoptosis have led to an increased interest in PKR modulation as an antitumor strategy. PKR can either be up-regulated through direct induction by the transcription factor E2F-1, or it can be activated through direct protein-protein interactions with the melanoma differentiation-associated gene-7 (MDA7, IL-24). Additionally, the intracellular formation of double-stranded RNA by transfection with antisense RNA complementary to tumor-specific RNA sequences can induce PKR activation and apoptosis selective to these tumor cells. The growing application of viral vector-based gene therapies and oncolytic, replicating viruses that must elude viral defense in order to be effective, has also drawn attention to PKR. Oncolytic viruses, like the attenuated herpes simplex virus R3616, the vesicular stomatitis virus, or reovirus, specifically replicate in tumor cells only because the viral host defense in the permissive cells is suppressed. In this article we review the role of PKR as an effector of apoptosis and a target for tumor treatment strategies and discuss the potential of PKR-modifying agents to treat patients with cancer. Targeted gene therapy against cancer can be approached by activation of PKR with the down-regulation of protein synthesis and induction of apoptosis, or by suppression of PKR with the propagation of oncolytic virus. Since the PKR pathway can be modified by many routes, antitumor therapies combining oncolytic virus, gene therapies, and chemotherapy with PKR modifiers are likely to emerge in the near future as therapeutic options in the treatment of patients with cancer.
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Affiliation(s)
- Stephan A Vorburger
- Department of Surgical Oncology, The University of Texas M D Anderson Cancer Center, Houston, Texas 77030, USA
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Vorburger SA, Pataer A, Yoshida K, Barber GN, Xia W, Chiao P, Ellis LM, Hung MC, Swisher SG, Hunt KK. Role for the double-stranded RNA activated protein kinase PKR in E2F-1-induced apoptosis. Oncogene 2002; 21:6278-88. [PMID: 12214268 DOI: 10.1038/sj.onc.1205761] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2002] [Revised: 06/06/2002] [Accepted: 06/14/2002] [Indexed: 02/04/2023]
Abstract
The transcription factor E2F-1 induces cell cycle progression at the G1/S checkpoint, and deregulation of E2F-1 provokes apoptosis in a wide variety of malignant cells. To date only p14(ARF) and p73, a p53 homologue, have been identified as E2F-1-inducible genes capable of mediating an apoptotic response. Here we show that adenovirus-mediated E2F-1 overexpression in cancer cells induces expression and autophosphorylation of the double-stranded RNA-dependent protein kinase PKR leading to phosphorylation of its downstream target, the alpha-subunit of the eukaryotic translation initiation factor 2 (eIF-2alpha) and to apoptotic cell death. This PKR-dependent apoptosis occurs in cell lines with mutated p53 and in cell lines with mutated p53 and p73, and is significantly reduced by the chemical inhibition of PKR activation. Further, PKR(-/-) mouse embryo fibroblasts, but not PKR(+/+) mouse embryo fibroblasts, demonstrate significant resistance to E2F-1-induced apoptosis. We conclude that an important pathway of E2F-1-mediated apoptosis is dependent on PKR activation and does not require p53 or p73.
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Affiliation(s)
- Stephan A Vorburger
- Department of Surgical Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, TX 77030, USA
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Ward SV, Samuel CE. Regulation of the interferon-inducible PKR kinase gene: the KCS element is a constitutive promoter element that functions in concert with the interferon-stimulated response element. Virology 2002; 296:136-46. [PMID: 12036325 DOI: 10.1006/viro.2002.1356] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The RNA-dependent protein kinase PKR plays important roles in the antiviral and antiproliferative actions of IFN. The IFN-inducible promoter of the human PKR gene contains a 15-bp DNA element designated KCS. The KCS element is located 4 bp upstream of the interferon-stimulated response element (ISRE) and is required for both basal and IFN-inducible transcription. We have examined the effect of insertion mutations between the KCS and the ISRE elements, as well as altered orientation of the KCS element relative to the ISRE element, to assess a possible functional interaction between them. Large insertions (>or=93 bp) between the KCS and ISRE elements significantly reduced both basal and IFN-inducible promoter activity. The function of the KCS element was dependent on the orientation of KCS relative to the ISRE element. Multimerization of the KCS element increased both basal and IFN-inducible transcription. Electrophoretic mobility shift analyses (EMSA) identified IFN-inducible protein complex formation that required both the KCS and the ISRE DNA element sequences. The novel IFN-inducible protein complexes contained the transcription factor STAT1, as shown by supershift analyses and by their presence in extracts prepared from STAT1 wild-type but not from STAT1-/- null cells. These results, taken together, strongly suggest that the KCS and ISRE elements of the human PKR promoter represent a functional unit.
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Affiliation(s)
- Simone Visosky Ward
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA
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