Gene Summary

Gene:PPP1R15A; protein phosphatase 1 regulatory subunit 15A
Aliases: GADD34
Summary:This gene is a member of a group of genes whose transcript levels are increased following stressful growth arrest conditions and treatment with DNA-damaging agents. The induction of this gene by ionizing radiation occurs in certain cell lines regardless of p53 status, and its protein response is correlated with apoptosis following ionizing radiation. [provided by RefSeq, Jul 2008]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:protein phosphatase 1 regulatory subunit 15A
Source:NCBIAccessed: 30 August, 2019


What does this gene/protein do?
Show (10)

Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 30 August 2019 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.

  • Neoplasm Proteins
  • eIF-2 Kinase
  • Dose-Response Relationship, Drug
  • Neoplastic Cell Transformation
  • Cell Cycle Proteins
  • Antigens, Differentiation
  • Messenger RNA
  • Transcriptional Activation
  • Oligonucleotide Array Sequence Analysis
  • Molecular Sequence Data
  • Proteins
  • DNA-Binding Proteins
  • Signal Transducing Adaptor Proteins
  • Cell Division
  • Apoptosis
  • Skin Cancer
  • Phosphorylation
  • Cell Cycle
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins
  • Transfection
  • Vascular Endothelial Growth Factors
  • Chromosome 19
  • Cancer Gene Expression Regulation
  • Signal Transduction
  • Biomarkers, Tumor
  • Up-Regulation
  • DNA Damage
  • Intracellular Signaling Peptides and Proteins
  • Antineoplastic Agents
  • HSP70 Heat-Shock Proteins
  • Transcription Factor CHOP
  • Transcription Factors
  • Melanoma
  • Protein Phosphatase 1
  • Sequence Homology
  • Disease Progression
  • CCAAT-Enhancer-Binding Proteins
  • Gene Expression Profiling
Tag cloud generated 30 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (2)

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: PPP1R15A (cancer-related)

Gerresheim GK, Bathke J, Michel AM, et al.
Cellular Gene Expression during Hepatitis C Virus Replication as Revealed by Ribosome Profiling.
Int J Mol Sci. 2019; 20(6) [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Hepatitis C virus (HCV) infects human liver hepatocytes, often leading to liver cirrhosis and hepatocellular carcinoma (HCC). It is believed that chronic infection alters host gene expression and favors HCC development. In particular, HCV replication in Endoplasmic Reticulum (ER) derived membranes induces chronic ER stress. How HCV replication affects host mRNA translation and transcription at a genome wide level is not yet known.
METHODS: We used Riboseq (Ribosome Profiling) to analyze transcriptome and translatome changes in the Huh-7.5 hepatocarcinoma cell line replicating HCV for 6 days.
RESULTS: Established viral replication does not cause global changes in host gene expression-only around 30 genes are significantly differentially expressed. Upregulated genes are related to ER stress and HCV replication, and several regulated genes are known to be involved in HCC development. Some mRNAs (
CONCLUSION: After establishing HCV replication, the lack of global changes in cellular gene expression indicates an adaptation to chronic infection, while the downregulation of mitochondrial respiratory chain genes indicates how a virus may further contribute to cancer cell-like metabolic reprogramming ("Warburg effect") even in the hepatocellular carcinoma cells used here.

Shahzad MMK, Felder M, Ludwig K, et al.
Trans10,cis12 conjugated linoleic acid inhibits proliferation and migration of ovarian cancer cells by inducing ER stress, autophagy, and modulation of Src.
PLoS One. 2018; 13(1):e0189524 [PubMed] Free Access to Full Article Related Publications
The goal of this study was to investigate the anti-cancer effects of Trans10,cis12 conjugated linoleic acid (t10,c12 CLA). MTT assays and QCM™ chemotaxis 96-wells were used to test the effect of t10,c12 CLA on the proliferation and migration and invasion of cancer cells. qPCR and Western Blotting were used to determine the expression of specific factors. RNA sequencing was conducted using the Illumina platform and apoptosis was measured using a flow cytometry assay. t10,c12 CLA (IC50, 7 μM) inhibited proliferation of ovarian cancer cell lines SKOV-3 and A2780. c9,t11 CLA did not attenuate the proliferation of these cells. Transcription of 165 genes was significantly repressed and 28 genes were elevated. Genes related to ER stress, ATF4, CHOP, and GADD34 were overexpressed whereas EDEM2 and Hsp90, genes required for proteasomal degradation of misfolded proteins, were downregulated upon treatment. While apoptosis was not detected, t10,c12 CLA treatment led to 9-fold increase in autophagolysosomes and higher levels of LC3-II. G1 cell cycle arrest in treated cells was correlated with phosphorylation of GSK3β and loss of β-catenin. microRNA miR184 and miR215 were upregulated. miR184 likely contributed to G1 arrest by downregulating E2F1. miR215 upregulation was correlated with increased expression of p27/Kip-1. t10,c12 CLA-mediated inhibition of invasion and migration correlated with decreased expression of PTP1b and decreased Src activation by inhibiting phosphorylation at Tyr416. Due to its ability to inhibit proliferation and migration, t10,c12 CLA should be considered for treatment of ovarian cancer.

Song Y, Liu S, Zhao Z, et al.
Relationship between PPP1R15A gene polymorphism (rs611251) and Epstein-Barr virus-associated tumors.
Acta Virol. 2017; 61(4):445-452 [PubMed] Related Publications
Protein phosphatase 1, regulatory subunit 15A (PPP1R15A), also known as growth arrest and DNA damage-inducible protein GADD34, plays a vital role in promoting cell death and the unfolded protein response (UPR). In order to explore whether the SNP (rs611251) of PPP1R15A gene has a role in different types of Epstein-Barr virus (EBV) - associated tumors, we detected the PPP1R15A gene rs611251 polymorphism in 195 cases of EBV positive tumors (93 lymphomas, 48 gastric carcinomas, 54 nasopharyngeal carcinomas), 208 cases of EBV-negative tumors (136 gastric carcinoma, 19 nasopharyngeal carcinomas, 53 lymphomas) and 113 peripheral blood samples from healthy individuals. Compared with normal controls, the wild type TT and allele T of rs611251 showed higher frequency in gastric carcinoma (GCs), nasopharyngeal carcinomas (NPCs) and lymphomas. However, there was no significant difference between EBV-associated gastric (EBVaGC) and EBVnGC, EBV-positive NPCs and EBV-negative NPCs, EBV-related lymphomas and EBV-negative lymphomas in rs611251 of PPP1R15A. In conclusion, the PPP1R15A rs611251 polymorphism was significantly related to three kinds of tumors. Nevertheless, EBV has no obvious effect on PPP1R15A rs611251 polymorphism of NPC, GC and lymphoma. What's more, the genotype TT and allele T could be risk factors for NPC, GC and lymphoma. Our study explores the relationship between PPP1R15A gene polymorphism (rs611251) and Epstein-Barr virus-associated tumors for the first time. PPP1R15A gene SNP (rs611251) have association with multiple tumor types, which may provide some new clues to the detection and treatment of tumors.

Juang SH, Chiang CY, Liang FP, et al.
Mechanistic Study of Tetrahydrofuran- acetogenins In Triggering Endoplasmic Reticulum Stress Response-apotoposis in Human Nasopharyngeal Carcinoma.
Sci Rep. 2016; 6:39251 [PubMed] Free Access to Full Article Related Publications
For past three decades, numerous studies have elucidated the antiproliferative effects of acetogenins in hopes of developing a new class of clinical anticancer agents. However, clear and definitive action mechanisms of acetogenins were less clarified. In the present study, three tetrahydrofuran (THF)-containing acetogenins were found to have potent and selective antiproliferative activity against human nasopharyngeal carcinoma (NPC) cell lines and their methotrexate-resistant counterparts. The THF-containing acetogenins induced G

Stone S, Ho Y, Li X, et al.
Dual role of the integrated stress response in medulloblastoma tumorigenesis.
Oncotarget. 2016; 7(39):64124-64135 [PubMed] Free Access to Full Article Related Publications
In response to endoplasmic reticulum (ER) stress, activation of pancreatic ER kinase (PERK) coordinates an adaptive program known as the integrated stress response (ISR) by phosphorylating translation initiation factor 2α (eIF2α). Phosphorylated eIF2α is quickly dephosphorylated by the protein phosphatase 1 and growth arrest and DNA damage 34 (GADD34) complex. Data indicate that the ISR can either promote or suppress tumor development. Our previous studies showed that the ISR is activated in medulloblastoma in both human patients and animal models, and that the decreased ISR via PERK heterozygous deficiency attenuates medulloblastoma formation in Patched1 heterozygous deficient (Ptch1+/-) mice by enhancing apoptosis of pre-malignant granule cell precursors (GCPs) during cell transformation. We showed here that GADD34 heterozygous mutation moderately enhanced the ISR and noticeably increased the incidence of medulloblastoma in adult Ptch1+/- mice. Surprisingly, GADD34 homozygous mutation strongly enhanced the ISR, but significantly decreased the incidence of medulloblastoma in adult Ptch1+/- mice. Intriguingly, GADD34 homozygous mutation significantly enhanced pre-malignant GCP apoptosis in cerebellar hyperplastic lesions and reduced the lesion numbers in young Ptch1+/- mice. Nevertheless, neither GADD34 heterozygous mutation nor GADD34 homozygous mutation had a significant effect on medulloblastoma cells in adult Ptch1+/- mice. Collectively, these data imply the dual role of the ISR, promoting and inhibiting, in medulloblastoma tumorigenesis by regulating apoptosis of pre-malignant GCPs during the course of malignant transformation.

Teoh PJ, Bi C, Sintosebastian C, et al.
PRIMA-1 targets the vulnerability of multiple myeloma of deregulated protein homeostasis through the perturbation of ER stress via p73 demethylation.
Oncotarget. 2016; 7(38):61806-61819 [PubMed] Free Access to Full Article Related Publications
Despite therapeutic advancement, multiple myeloma (MM) remains incurable with drug resistance being one of the main challenges in the clinic. Myeloma cells possess high protein secretory load, leading to increased intracellular endoplasmic reticulum (ER) stress. Hence, they are vulnerable to further perturbation to its protein homeostasis. In studying the therapeutic mechanism of PRIMA-1 (mutant-p53-reactivating-agent), we uncovered its novel p53-independent-mechanism that can be exploited for myeloma. Despite its inability in restoring the wild type-p53 protein conformation and transcriptional function in the mutant-p53-human-myeloma-cells, PRIMA-1 was efficacious against myeloma cells with differential p53 genotypes. Strikingly, cells without p53 expression demonstrated highest drug sensitivity. Genome-wide gene-expression analysis revealed the involvement of ER stress/UPR-pathway in inducing PRIMA-1-toxicity. UPR markers, HSP70, CHOP and GADD34, were significantly up-regulated, concomitantly with the induction of apoptosis. Furthermore, there was a global attenuation of protein synthesis, correlated with phospho-eIF2a up-regulation. Mechanistically, we identified that PRIMA-1 could cause the demethylation of TP73, through DNMT1 depletion, to subsequently enhance UPR. Of clinical significance, we observed that PRIMA-1 had additive therapeutic effects with another UPR-inducing-agent, bortezomib. Importantly, it can partially re-sensitize bortezomib-resistant cells to bortezomib. Given that MM is already stressed at the baseline in the ER, our results implicated that PRIMA-1 is a potential therapeutic option in MM by targeting its Achilles heel.

Palam LR, Gore J, Craven KE, et al.
Integrated stress response is critical for gemcitabine resistance in pancreatic ductal adenocarcinoma.
Cell Death Dis. 2015; 6:e1913 [PubMed] Free Access to Full Article Related Publications
Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with marked chemoresistance and a 5-year survival rate of 7%. The integrated stress response (ISR) is a cytoprotective pathway initiated in response to exposure to various environmental stimuli. We used pancreatic cancer cells (PCCs) that are highly resistant to gemcitabine (Gem) and an orthotopic mouse model to investigate the role of the ISR in Gem chemoresistance. Gem induced eIF2 phosphorylation and downstream transcription factors ATF4 and CHOP in PCCs, and these effects occurred in an eIF2α-S51 phosphorylation-dependent manner as determined using PANC-1 cells, and wild type and S51 mutant mouse embryo fibroblasts. Blocking the ISR pathway in PCCs with the ISR inhibitor ISRIB or siRNA-mediated depletion of ATF4 resulted in enhanced Gem-mediated apoptosis. Polyribosomal profiling revealed that Gem caused repression of global translation and this effect was reversed by ISRIB or by expressing GADD34 to facilitate eIF2 dephosphorylation. Moreover, Gem promoted preferential mRNA translation as determined in a TK-ATF4 5'UTR-Luciferase reporter assay, and this effect was also reversed by ISRIB. RNA-seq analysis revealed that Gem upregulated eIF2 and Nrf2 pathways, and that ISRIB significantly inhibited these pathways. Gem also induced the expression of the antiapoptotic factors Nupr1, BEX2, and Bcl2a1, whereas ISRIB reduced their expression. In an orthotopic tumor model using PANC-1 cells, ISRIB facilitated Gem-mediated increases in PARP cleavage, which occurred in conjunction with decreased tumor size. These findings indicate that Gem chemoresistance is enhanced by activating multiple ISR-dependent pathways, including eIF2, Nrf2, Nupr1, BEX2, and Bcl2A1. It is suggested that targeting the ISR pathway may be an efficient mechanism for enhancing therapeutic responsiveness to Gem in PDAC.

Yu X, Xia W, Li S, et al.
Antitumor effect and underlying mechanism of RGD-modified adenovirus mediated IL-24 expression on myeloid leukemia cells.
Int Immunopharmacol. 2015; 28(1):560-70 [PubMed] Related Publications
Interleukin-24 (IL-24), a member of the IL-10 cytokine gene family, causes growth suppression and apoptosis in various solid tumor cells. However, the effects of IL-24 on hematopoietic malignant cells have not been extensively explored. In this report, we constructed an RGD-engineered recombinant adenoviral vector, Ad.RGD-IL-24, and assessed its effects on human myeloid leukemia cells. Ad vector mediates gene transfer into leukemia cells with high efficiency. Ectopic over-expression of IL-24 has significant growth inhibition and differentiation inducement effects on these cells. Treatment with Ad.RGD-IL-24 could potentially induce leukemia cells' cell-cycle arrest. In addition, IL-24 expression could significantly induce apoptosis of the THP-1 cells. Ad.RGD-IL-24 had a potent effect on the up-regulation of the expression of GRP78/Bip, GADD34 and Bax, down-regulation of the expression of Bcl-2 and Mcl-1, and induced the activation of Caspase-3, which may be responsible for its apoptosis-inducing effect on THP-1 cells. Furthermore, IL-24 expression could retard transplanted leukemia cell tumor growth in vivo in athymic nude mice. These findings showed the marked antitumor activity of IL-24 and provided potential perspectives in designing therapeutic or vaccine strategies in immuno-gene therapy of myeloid leukemia.

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.

Panth KM, Leijenaar RT, Carvalho S, et al.
Is there a causal relationship between genetic changes and radiomics-based image features? An in vivo preclinical experiment with doxycycline inducible GADD34 tumor cells.
Radiother Oncol. 2015; 116(3):462-6 [PubMed] Related Publications
BACKGROUND AND PURPOSE: The central hypothesis of "radiomics" is that imaging features reflect tumor phenotype and genotype. Until now only correlative studies have been performed. The main objective of our study is to determine whether a causal relationship exists between genetic changes and image features. The secondary objective is to assess whether the combination with radiotherapy (RT) influences these image features.
MATERIAL AND METHODS: HCT116 doxycycline (dox) inducible GADD34 cells were grown as xenografts in the flanks of NMRI-nu mice. GADD34 overexpression decreases hypoxic fraction. Radiomics analyses were performed on computed tomography images obtained at 40kVp and again at 80kVp for validation, before radiotherapy at a volume of 200mm(3), 4days post RT (10Gy) and 500mm(3). To select reproducible features test-retest experiments were performed at baseline.
RESULTS: Gene induction and/or irradiation translated into significant changes in radiomics features. Post irradiation, 17 features for 40kVp and 9 features for 80kVp differed significantly between dox+ and dox- combined with RT. 8 and 4 of these features remained consistent for 40 and 80kVp, respectively.
CONCLUSION: Radiomics is able to identify early effects of changed gene expression combined with radiation treatment in tumors with similar volumes which are not visible to human eye.

Aveic S, Viola G, Accordi B, et al.
Targeting BAG-1: a novel strategy to increase drug efficacy in acute myeloid leukemia.
Exp Hematol. 2015; 43(3):180-190.e6 [PubMed] Related Publications
Overexpression of antiapoptotic proteins occurs frequently in cancer, resulting in defective apoptosis that may contribute to a poor chemosensitivity of tumor cells. B-cell lymphoma (BCL) 2-associated AthanoGene-1 (BAG-1) is a prosurvival chaperone recently found involved in the maintenance of acute myeloid leukemia (AML) cells survival in vitro. Here we reported BAG-1 upregulation in 87 of 99 analyzed AML patients with respect to healthy control samples applying reverse phase protein assay. Silencing of BAG-1 expression confirmed a decreased BCL-2 protein level but, in addition, provoked the increased transcription of GADD34 stress sensor. Furthermore, a dephosphorylation of eIF2α, as well as alteration of expression of IRE-1 and CHOP proteins, were documented, suggesting that a disruption of the endoplasmic reticulum stress/unfolded protein response was provoked by downregulation of BAG-1. A similar phenomenon was triggered after addition of Thioflavin S, which was shown to block BAG-1/BCL-2 interaction and to increase cell death, enforcing a prosurvival role of the BAG-1 protein in AML. Interestingly, synergic cytotoxic effects of doxorubicin, VP16 drugs, and ABT-737 compound were observed when Thioflavin S was coupled with these drugs. Taken together, our results gave further proof that upregulation of BAG-1 plays a critical role in AML and that BAG-1 targeting might be considered for a combined therapeutic strategy with conventional chemotherapy drugs in the treatment of AML patients.

Jiang X, Kanda T, Nakamoto S, et al.
Knockdown of glucose-regulated protein 78 enhances poly(ADP-ribose) polymerase cleavage in human pancreatic cancer cells exposed to endoplasmic reticulum stress.
Oncol Rep. 2014; 32(6):2343-8 [PubMed] Free Access to Full Article Related Publications
The present study examined the expression of glucose‑regulated protein 78 (GRP78/Bip) in human pancreatic cancer cell lines and the effect of knockdown of GRP78 on the cleavage of poly(ADP-ribose) polymerase (PARP). Human pancreatic cancer cell lines (KP-2, MIAPaCa-2, Panc-1 and SUIT-2), constitutively expressed GRP78. We also demonstrated that ER stress induced by thapsigargin upregulated protein levels of GRP78. In the presence of thapsigargin, knockdown of GRP78 enhanced the PARP cleavage in the human pancreatic cancer cells. These results provide evidence that GRP78 is a potential therapeutic target for 'difficult-to-treat' pancreatic cancer, in which ER stress signaling in part falls into disorder.

Yong KJ, Milenic DE, Baidoo KE, Brechbiel MW
Impact of α-targeted radiation therapy on gene expression in a pre-clinical model for disseminated peritoneal disease when combined with paclitaxel.
PLoS One. 2014; 9(9):e108511 [PubMed] Free Access to Full Article Related Publications
To better understand the molecular basis of the enhanced cell killing effected by the combined modality of paclitaxel and ²¹²Pb-trastuzumab (Pac/²¹²Pb-trastuzumab), gene expression in LS-174T i.p. xenografts was investigated 24 h after treatment. Employing a real time quantitative PCR array (qRT-PCR array), 84 DNA damage response genes were quantified. Differentially expressed genes following therapy with Pac/²¹²Pb-trastuzumab included those involved in apoptosis (BRCA1, CIDEA, GADD45α, GADD45γ, GML, IP6K3, PCBP4, PPP1R15A, RAD21, and p73), cell cycle (BRCA1, CHK1, CHK2, GADD45α, GML, GTSE1, NBN, PCBP4, PPP1R15A, RAD9A, and SESN1), and damaged DNA repair (ATRX, BTG2, EXO1, FEN1, IGHMBP2, OGG1, MSH2, MUTYH, NBN, PRKDC, RAD21, and p73). This report demonstrates that the increased stressful growth arrest conditions induced by the Pac/²¹²Pb-trastuzumab treatment suppresses cell proliferation through the regulation of genes which are involved in apoptosis and damaged DNA repair including single and double strand DNA breaks. Furthermore, the study demonstrates that ²¹²Pb-trastuzumab potentiation of cell killing efficacy results from the perturbation of genes related to the mitotic spindle checkpoint and BASC (BRCA1-associated genome surveillance complex), suggesting cross-talk between DNA damage repair and the spindle damage response.

Hua KT, Wang MY, Chen MW, et al.
The H3K9 methyltransferase G9a is a marker of aggressive ovarian cancer that promotes peritoneal metastasis.
Mol Cancer. 2014; 13:189 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Ovarian cancer (OCa) peritoneal metastasis is the leading cause of cancer-related deaths in women with limited therapeutic options available for treating it and poor prognosis, as the underlying mechanism is not fully understood.
METHOD: The clinicopathological correlation of G9a expression was assessed in tumor specimens of ovarian cancer patients. Knockdown or overexpression of G9a in ovarian cancer cell lines was analysed with regard to its effect on adhesion, migration, invasion and anoikis-resistance. In vivo biological functions of G9a were tested by i.p. xenograft ovarian cancer models. Microarray and quantitative RT-PCR were used to analyze G9a-regulated downstream target genes.
RESULTS: We found that the expression of histone methyltransferase G9a was highly correlated with late stage, high grade, and serous-type OCa. Higher G9a expression predicted a shorter survival in ovarian cancer patients. Furthermore, G9a expression was higher in metastatic lesions compared with their corresponding ovarian primary tumors. Knockdown of G9a expression suppressed prometastatic cellular activities including adhesion, migration, invasion and anoikis-resistance of ovarian cancer cell lines, while G9a over-expression promoted these cellular properties. G9a depletion significantly attenuated the development of ascites and tumor nodules in a peritoneal dissemination model. Importantly, microarray and quantitative RT-PCR analysis revealed that G9a regulates a cohort of tumor suppressor genes including CDH1, DUSP5, SPRY4, and PPP1R15A in ovarian cancer. Expression of these genes was also inversely correlated with G9a expression in OCa specimens.
CONCLUSION: We propose that G9a contributes to multiple steps of ovarian cancer metastasis and represents a novel target to combat this deadly disease.

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.

Mujcic H, Nagelkerke A, Rouschop KM, et al.
Hypoxic activation of the PERK/eIF2α arm of the unfolded protein response promotes metastasis through induction of LAMP3.
Clin Cancer Res. 2013; 19(22):6126-37 [PubMed] Related Publications
PURPOSE: Conditions of poor oxygenation (hypoxia) are present in many human tumors, including cervix cancer, and are associated with increased risk of metastasis and poor prognosis. Hypoxia is a potent activator of the PERK/eIF2α signaling pathway, a component of the unfolded protein response (UPR) and an important mediator of hypoxia tolerance and tumor growth. Here, the importance of this pathway in the metastasis of human cervix carcinoma was investigated.
EXPERIMENTAL DESIGN: Amplification and expression of LAMP3, a UPR metastasis-associated gene, was examined using FISH and immunofluorescence in a cohort of human cervix tumors from patients who had received oxygen needle electrode tumor oxygenation measurements. To evaluate the importance of this pathway in metastasis in vivo, we constructed a series of inducible cell lines to interfere with PERK signaling during hypoxia and used these in an orthotopic cervix cancer model of hypoxia-driven metastasis.
RESULTS: We show that LAMP3 expression in human cervix tumors is augmented both by gene copy number alterations and by hypoxia. Induced disruption of PERK signaling in established orthotopic xenografts resulted in complete inhibition of hypoxia-induced metastasis to the lymph nodes. This is due, in part, to a direct influence of the UPR pathway on hypoxia tolerance. However, we also find that LAMP3 is a key mediator of hypoxia-driven nodal metastasis, through its ability to promote metastatic properties including cell migration.
CONCLUSION: These data suggest that the association between hypoxia, metastasis, and poor prognosis is due, in part, to hypoxic activation of the UPR and expression of LAMP3. Clin Cancer Res; 19(22); 6126-37. ©2013 AACR.

Mukai R, Ohshima T
HTLV-1 HBZ positively regulates the mTOR signaling pathway via inhibition of GADD34 activity in the cytoplasm.
Oncogene. 2014; 33(18):2317-28 [PubMed] Related Publications
Human T-cell leukemia virus type-1 (HTLV-1) infection causes adult T-cell leukemia (ATL). Modulation of the transcriptional control of cellular genes by HTLV-1 is thought to be associated with the development of ATL. The viral protein HTLV-1 basic leucine-zipper factor (HBZ) has been shown to dysregulate the activity of cellular transcription factors. Here, we demonstrate that HBZ is exported from the nucleus to the cytoplasm, where it activates the mammalian target of rapamycin (mTOR) signaling pathway through an association with growth arrest and DNA damage gene 34 (GADD34). The N-terminal region of HBZ interacts with the C-terminal region of GADD34. HBZ contains a functional nuclear export signal (NES) sequence within its N-terminal region and it is exported from the nucleus via the CRM1-dependent pathway. Nuclear export of HBZ is essential for its interaction with GADD34 and increased phosphorylation of S6 kinase, which is an established downstream target of the mTOR pathway. Starvation-induced autophagy is significantly suppressed by the overexpression of HBZ. These findings indicate that HBZ is actively exported to the cytoplasm, where it dysregulates the function of cellular factors.

Karlisch C, Harati K, Chromik AM, et al.
Effects of TRAIL and taurolidine on apoptosis and proliferation in human rhabdomyosarcoma, leiomyosarcoma and epithelioid cell sarcoma.
Int J Oncol. 2013; 42(3):945-56 [PubMed] Related Publications
Soft tissue sarcomas (STS) are a heterogeneous group of malignant tumours representing 1% of all malignancies in adults. Therapy for STS should be individualised and multimodal, but complete surgical resection with clear margins remains the mainstay of therapy. Disseminated soft tissue sarcoma still represents a therapeutic dilemma. Commonly used chemotherapeutic agents such as doxorubicin and ifosfamide have proven to be effective in fewer than 30% in these cases. Therefore, we tested the apoptotic and anti-proliferative in vitro effects of TNF-related apoptosis-inducing ligand (TRAIL) and taurolidine (TRD) on rhabdomyosarcoma (A-204), leiomyosarcoma (SK-LMS-1) and epithelioid cell sarcoma (VA-ES-BJ) cell lines. Viability, apoptosis and necrosis were quantified by FACS analysis (propidium iodide/Annexin V staining). Gene expression was analysed by DNA microarrays and the results validated for selected genes by rtPCR. Protein level changes were documented by western blot analysis. Cell proliferation was analysed by BrdU ELISA assay. The single substances TRAIL and TRD significantly induced apoptotic cell death and decreased proliferation in rhabdomyosarcoma and epithelioid cell sarcoma cells. The combined use of TRAIL and TRD resulted in a synergistic apoptotic effect in all three cell lines, especially in rhabdomyosarcoma cells leaving 18% viable cells after 48 h of incubation (p<0.05). Analysis of the differentially regulated genes revealed that TRD and TRAIL influence apoptotic pathways, including the TNF-receptor associated and the mitochondrial pathway. Microarray analysis revealed remarkable expression changes in a variety of genes, which are involved in different apoptotic pathways and cross talk to other pathways at multiple levels. This in vitro study demonstrates that TRAIL and TRD synergise in inducing apoptosis and inhibiting proliferation in different human STS cell lines. Effects on gene expression differ relevantly in the sarcoma entities. These results provide experimental support for in vivo trials assessing the effect of TRAIL and TRD in STS and sustain the approach of individualized therapy.

Zhang KJ, Zhang J, Wu YM, et al.
Complete eradication of hepatomas using an oncolytic adenovirus containing AFP promoter controlling E1A and an E1B deletion to drive IL-24 expression.
Cancer Gene Ther. 2012; 19(9):619-29 [PubMed] Related Publications
Interleukin (IL)-24, a promising therapeutic gene, has been widely used for Cancer Targeting Gene-Viro-Therapy (CTGVT). In this study, IL-24 was inserted into an oncolytic adenovirus in which the E1A gene is driven by an enhanced, short α-fetoprotein (AFP) promoter and the E1B gene is completely deleted to form Ad.enAFP-E1A-ΔE1B-IL-24. This construct has a potent antitumor effect on liver cancer cell lines in vitro, but little or no effect on normal cell lines, such as L-02 and QSG-7701. In vivo, the complete elimination of Huh-7 liver cancer in nude mice with Ad.enAFP-E1A-ΔE1B-IL-24 intratumor injection was observed. The design of Ad.enAFP-E1A-ΔE1B-IL-24 and its potent antitumor effect on liver cancer have not been published previously. The mechanism of the potent antitumor effect of Ad.enAFP-E1A-ΔE1B-IL-24 is due to the upregulation of GADD34 and intrinsic and extrinsic apoptotic signaling.

Fribley AM, Cruz PG, Miller JR, et al.
Complementary cell-based high-throughput screens identify novel modulators of the unfolded protein response.
J Biomol Screen. 2011; 16(8):825-35 [PubMed] Free Access to Full Article Related Publications
Despite advances toward understanding the prevention and treatment of many cancers, patients who suffer from oral squamous cell carcinoma (OSCC) confront a survival rate that has remained unimproved for more than 2 decades, indicating our ability to treat them pharmacologically has reached a plateau. In an ongoing effort to improve the clinical outlook for this disease, we previously reported that an essential component of the mechanism by which the proteasome inhibitor bortezomib (PS-341, Velcade) induced apoptosis in OSCC required the activation of a terminal unfolded protein response (UPR). Predicated on these studies, the authors hypothesized that high-throughput screening (HTS) of large diverse chemical libraries might identify more potent or selective small-molecule activators of the apoptotic arm of the UPR to control or kill OSCC. They have developed complementary cell-based assays using stably transfected CHO-K1 cell lines that individually assess the PERK/eIF2α/CHOP (apoptotic) or the IRE1/XBP1 (adaptive) UPR subpathways. An 66 K compound collection was screened at the University of Michigan Center for Chemical Genomics that included a unique library of prefractionated natural product extracts. The mycotoxin methoxycitrinin was isolated from a natural extract and found to selectively activate the CHOP-luciferase reporter at 80 µM. A series of citrinin derivatives was isolated from these extracts, including a unique congener that has not been previously described. In an effort to identify more potent compounds, the authors examined the ability of citrinin and the structurally related mycotoxins ochratoxin A and patulin to activate the UPR. Strikingly, it was found that patulin at 2.5 to 10 µM induced a terminal UPR in a panel of OSCC cells that was characterized by an increase in CHOP, GADD34, and ATF3 gene expression and XBP1 splicing. A luminescent caspase assay and the induction of several BH3-only genes indicated that patulin could induce apoptosis in OSCC cells. These data support the use of this complementary HTS strategy to identify novel modulators of UPR signaling and tumor cell death.

Zhang XQ, Yang Z, Benedict WF
Direct gene transfer of adenoviral-mediated interferon α into human bladder cancer cells but not the bystander factors produced induces endoplasmic reticulum stress-related cytotoxicity.
Cancer Gene Ther. 2011; 18(4):260-4 [PubMed] Free Access to Full Article Related Publications
We have previously shown that adenoviral-mediated interferon α (Ad-IFNα) is cytotoxic both to cells that are sensitive to recombinant interferon α (IFNα) and to cells which are resistant to IFNα. The cancer cell-specific cytotoxic effects of Ad-IFNα involve three different mechanisms: 1. The direct effect of IFNα production causing cancer cell death in IFNα sensitive cells (1); 2. The direct effect of Ad-IFNα infection and high levels of IFNα expression in IFNα resistant cancer cells (2); and 3. The indirect effect of the Ad-IFNα bystander factors produced (2-4). After Ad-IFNα infection, the cells produce a large amount of perinuclear localized IFN protein. This protein over-load could be a major factor in the direct cancer cell death of those cells infected with Ad-IFNα compared with the indirect cytotoxic effects of the bystander factors produced. Here, we investigated whether a component of Ad-IFN-induced cell death involves protein overload-induced endoplasmic reticulum (ER) stress, using an IFNα-resistant human bladder cancer cell line (KU7), and the normal human urothelial cell line, TERT-NHUC, as preclinical models. We found that the two ER stress response pathways examined were activated in KU7 cells. In contrast, following treatment of the normal TERT-NHUC cells with Ad-IFNα, no ER stress signals were observed. In addition, no ER stress related changes were seen, when KU7 cells were exposed to conditioned medium from Ad-IFNα-treated KU7 cells, indicating that bystander produced cytotoxicity did not involve ER stress. After 24 h of Ad-IFNα infection, the KU7 cancer cells produced spliced X-box binding protein 1 and activating transcription factor 6 protein (ATF6), evoking an ER stress response that could contribute to Ad-IFNα induced apoptosis in these cancer cells. In addition, GADD153/CHOP, GADD34 and BAX were also subsequently modified following activation of the ER stress pathways, thereby signaling downstream effectors in a pro-apoptotic manner.

Rahmani M, Mayo M, Dash R, et al.
Melanoma differentiation associated gene-7/interleukin-24 potently induces apoptosis in human myeloid leukemia cells through a process regulated by endoplasmic reticulum stress.
Mol Pharmacol. 2010; 78(6):1096-104 [PubMed] Free Access to Full Article Related Publications
Melanoma differentiation associated gene-7 (mda-7)/interleukin-24 (IL-24), a member of the IL-10 cytokine gene family, preferentially induces cell death in neoplastic epithelial cells types while sparing their normal counterparts. The effects of mda-7/IL-24 in acute myeloid leukemia (AML) cells have not been extensively characterized. Treatment with recombinant GST-MDA-7/IL-24 potently induced apoptosis in diverse myeloid leukemia cell types including U937, HL60, MV4-11, EOL-1, and MLL/ENL cells. MDA-7/IL-24 also markedly induced apoptosis in and suppressed the colony-forming capacity of primary AML blasts but exerted minimal toxicity toward normal CD34(+) hematopoietic progenitor cells. MDA-7/IL-24 lethality was associated with pronounced endoplasmic reticulum (ER) stress induction in leukemia cell lines and primary AML blasts, manifested by the accumulation of growth arrest and DNA damage-inducible protein 34 (GADD34), 78-kDa glucose-regulated protein (GRP78)/BiP, inositol-requiring enzyme 1α (IRE1α), and eukaryotic initiation factor 2α phosphorylation. It is noteworthy that short hairpin RNA (shRNA) knockdown of IRE1α, GADD34, or GRP78/BiP significantly enhanced MDA-7/IL-24-mediated apoptosis, indicating a protective role for these molecules against MDA-7/IL-24 lethality. MDA-7/IL-24 also down-regulated the antiapoptotic protein Mcl-1 and sharply increased expression of the proapoptotic proteins Bim and Noxa. Ectopic Mcl-1 expression or shRNA knockdown of Bim or Noxa significantly attenuated MDA-7/IL-24-mediated leukemia cell death. Finally, knockdown of Bax or Bak significantly reduced MDA-7/IL-24 lethality. Together, these findings indicate that MDA-7/IL-24 potently induces apoptosis in human myeloid leukemia cells through a process regulated by ER stress induction, Mcl-1 down-regulation, and Bim and Noxa up-regulation. They also suggest that MDA-7/IL-24 warrants further investigation in myeloid leukemia.

Hillegass JM, Blumen SR, Cheng K, et al.
Increased efficacy of doxorubicin delivered in multifunctional microparticles for mesothelioma therapy.
Int J Cancer. 2011; 129(1):233-44 [PubMed] Free Access to Full Article Related Publications
New and effective treatment strategies are desperately needed for malignant mesothelioma (MM), an aggressive cancer with a poor prognosis. We have shown previously that acid-prepared mesoporous microspheres (APMS) are nontoxic after intrapleural or intraperitoneal (IP) administration to rodents. The purpose here was to evaluate the utility of APMS in delivering chemotherapeutic drugs to human MM cells in vitro and in two mouse xenograft models of MM. Uptake and release of doxorubicin (DOX) alone or loaded in APMS (APMS-DOX) were evaluated in MM cells. MM cell death and gene expression linked to DNA damage/repair were also measured in vitro. In two severe combined immunodeficient mouse xenograft models, mice received saline, APMS, DOX or APMS-DOX injected directly into subcutaneous (SC) MM tumors or injected IP after development of human MMs peritoneally. Other mice received DOX intravenously (IV) via tail vein injections. In comparison to DOX alone, APMS-DOX enhanced intracellular uptake of DOX, MM death and expression of GADD34 and TP73. In the SC MM model, 3× weekly SC injections of APMS-DOX or DOX alone significantly inhibited tumor volumes, and systemic DOX administration was lethal. In mice developing IP MMs, significant (p < 0.05) inhibition of mesenteric tumor numbers, weight and volume was achieved using IP administration of APMS-DOX at one-third the DOX concentration required after IP injections of DOX alone. These results suggest APMS are efficacious for the localized delivery of lower effective DOX concentrations in MM and represent a novel means of treating intracavitary tumors.

Hoffman AE, Zheng T, Ba Y, et al.
Phenotypic effects of the circadian gene Cryptochrome 2 on cancer-related pathways.
BMC Cancer. 2010; 10:110 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Circadian genes continue to gain attention as important transcriptional regulators with the potential to influence a variety of biological pathways, including many cancer-related processes. The core circadian gene cryptochrome 2 (CRY2) is essential for proper circadian timing, and is a key component of the negative arm of the circadian feedback loop. As such, aberrant expression of CRY2 may influence carcinogenic processes and thereby impact cancer susceptibility.
METHODS: We silenced CRY2 in breast cancer cell lines (MCF-7) using small-interfering oligos (siRNA) and measured the impact of CRY2 knockdown on a number of cancer-relevant parameters. Cell cycle distribution, cell viability, and apoptotic response were measured in CRY2 knockdown (CRY2-) and normal (CRY2+) cell populations using flow cytometry in cells with and without exposure to a mutagen challenge. DNA damage accumulation was measured using the single cell gel electrophoresis (comet) assay, and damage was quantified using the Olive tail moment, which considers the amount and distance of DNA migration away from the nucleus, indicative of DNA strand breaks. Expression changes in cancer-relevant transcripts were measured by whole genome microarray. The Student's t-test was used for statistical comparisons, and P-values obtained from the microarray were adjusted for multiple comparisons using the false discovery rate correction, in order to obtain an adjusted Q-value for each observation.
RESULTS: The comet assay results indicated that upon exposure to the same dose of chemical mutagen, CRY2- cells accumulate significantly more unrepaired DNA damage than CRY2+ cells (P = 0.040), suggesting that CRY2 may be important for DNA repair. In addition, a number of transcripts with relevance for DNA damage repair displayed altered expression following CRY2 silencing. These included BCCIP (Q = 0.002), BCL2 (Q = 0.049), CCND1 (Q = 0.009), CDKN1A (Q < 0.001), GADD45A (Q = 0.002), HERC5 (Q < 0.001), MCM5 (Q = 0.042), PPP1R15A (Q < 0.001), SUMO1 (Q < 0.001), and UBA1 (Q = 0.023). However, no significant influence of CRY2 knockdown on cell cycle distributions, cell cycle checkpoints in response to mutagen challenge, or apoptotic response was detected.
CONCLUSIONS: In total, these data suggest a limited, but potentially important role for CRY2 in the regulation of DNA damage repair and the maintenance of genomic stability. Future investigations may focus on identifying the mechanisms by which CRY2 may regulate the expression of transcripts with known relevance for carcinogenesis.

Kato MA, Finley DJ, Lubitz CC, et al.
Selenium decreases thyroid cancer cell growth by increasing expression of GADD153 and GADD34.
Nutr Cancer. 2010; 62(1):66-73 [PubMed] Related Publications
Selenium (Se) supplementation is reported to decrease the incidence and total mortality of cancer. Whereas in vitro and in vivo studies have shown a decrease in prostate, lung, and liver cancers, this has not been shown in thyroid cancer. ARO (anaplastic), NPA (BRAF positive papillary), WRO (BRAF negative papillary), and FRO (follicular) cells treated with 150 microM seleno-l-methionine (SM) were assessed for viability at 24, 48, and 72 h. Treated FRO cells were examined for cell cycle using flow cytometry, for apoptosis using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, and for gene expression using microarray. Genes identified as upregulated were confirmed by real-time PCR (RT-PCR) and proteins by Western blot analysis. SM treatment significantly decreased the proliferation of all cell lines. TUNEL assay showed no evidence of apoptosis, and flow cytometry showed a significant cell-cycle arrest in S (271% increase, P = 0.006) and G2/M (61% increase, P = 0.002) compared to control. Microarray revealed 21 differentially expressed genes with greater than twofold change. A relative overexpression of growth arrest and DNA damage inducible (GADD)34 and GADD153 in treated cells was confirmed with RT-PCR and Western blot. SM inhibits thyroid cancer cell proliferation through a time dependent upregulation of the GADD family of genes and arrest in S and G2/M phases of the cell cycle. This is the first report of selenium induced inhibition of thyroid cancer cell growth.

Jiang XL, Du LL, Yang S, et al.
Suppression of teratocarcinoma growth by soluble TRAIL gene expression driven by the progression-elevated gene-3 promoter.
Cancer Biol Ther. 2009; 8(15):1517-24 [PubMed] Related Publications
A plasmid expressing the soluble tumor necrosis factor (TNF)-related apoptosis-inducing ligand, sTRAIL (amino acids 114-281 of TRAIL), driven by rat progression-elevated gene-3 (rPEG) promoter was constructed and evaluated. Transfection of embryonal carcinoma (EC) cells with the plasmid resulted in significant cellular apoptosis and elevated expression of death receptor 4 (DR4) and death receptor 5 (DR5). Direct intratumoral injection of DNA:liposome complexes suppressed tumor growth significantly and prolonged the survival of teratocarcinoma-bearing mice. Histological examination and serum analyses showed the absence of detectable toxicity in all examined tissues, including liver. Our results demonstrate that sTRAIL gene expression driven by the rPEG promoter may enable effective gene therapy against teratocarcinoma.

Zang C, Liu H, Bertz J, et al.
Induction of endoplasmic reticulum stress response by TZD18, a novel dual ligand for peroxisome proliferator-activated receptor alpha/gamma, in human breast cancer cells.
Mol Cancer Ther. 2009; 8(8):2296-307 [PubMed] Related Publications
Previously we reported that the peroxisome proliferator-activated receptor alpha/gamma dual ligand TZD18 inhibited growth and induced apoptosis of leukemia and glioblastoma cells. Now we show that TZD18 also has the same effects against six human breast cancer cell lines. To obtain insights into the mechanism involved in TZD18-induced growth inhibition and apoptosis in breast cancer, the gene expression profiles of TZD18-treated and untreated MCF-7 and MDA-MB-231 cells were compared by microarray analysis. Results reveal that many genes implicated in endoplasmic reticulum stress signaling, such as CHOP (also known as DDIT3 or GADD153), GRP78 (HSPA5), and ATF4, are highly up-regulated, suggesting endoplasmic reticulum stress is induced. This is supported by our data that treatment of MCF-7 and MDA-MB-231 cells with TZD18 induces phosphorylation of PERK and the alpha subunit of eukaryotic initiation factor 2 (eIF2alpha), as well as an up-regulation of GRP78 and an activation of ATF6, all of which are specific markers for endoplasmic reticulum stress. Furthermore, this ligand increases the endoplasmic reticulum stress-related cell death-regulators such as CHOP, DR5, GADD34, Bax, and Bak in these cells. Importantly, knockdown of CHOP by small interference RNA antagonizes the TZD18-induced apoptosis, indicating a crucial role of CHOP in the apoptotic process triggered by TZD18. In addition, TZD18 also activates stress-sensitive mitogen-activated protein kinase (MAPK) pathways including p38, ERK, and JNK. The specific inhibitors of these MAPKs attenuated the TZD18-induced growth inhibition in these cells. These results clearly show that activation of these MAPKs is important for TZD18-induced growth inhibition. In summary, TZD18-treatment leads to the activation of endoplasmic reticulum stress response and, subsequently, growth arrest and apoptosis in breast cancer cells.

Tardito S, Isella C, Medico E, et al.
The thioxotriazole copper(II) complex A0 induces endoplasmic reticulum stress and paraptotic death in human cancer cells.
J Biol Chem. 2009; 284(36):24306-19 [PubMed] Free Access to Full Article Related Publications
The copper(II) complex A0 induces a type of non-apoptotic cell death also known as paraptosis. Paraptosis involves extensive endoplasmic reticulum vacuolization in the absence of caspase activation. A wide panel of human cancer cell lines was used to demonstrate differences in cytotoxicity by the paraptosis-inducing drug A0 and the metal-based pro-apoptotic drug cisplatin. Gene expression profiling of the human fibrosarcoma HT1080 cells showed that, while cisplatin induced p53 targets, A0 up-regulated genes involved in the unfolded protein response (UPR) and response to heavy metals. The cytotoxic effects of A0 were associated with inhibition of the ubiquitin-proteasome system and accumulation of ubiquitinylated proteins, in a manner dependent on protein synthesis. Cycloheximide inhibited the accumulation of ubiquitinylated proteins and hampered A0-induced cell death process. The occurrence of the UPR during A0-induced death process was shown by the increased abundance of spliced XBP1 mRNA, transient eIF2alpha phosphorylation, and a series of downstream events, including attenuation of global protein synthesis and increased expression of ATF4, CHOP, BIP, and GADD34. Mouse embryonic fibroblasts expressing a mutant eIF2alpha, which could not be phosphorylated, were more resistant to A0 than wild type cells, pointing to a pro-death role of eIF2alpha phosphorylation. A0 may thus represent the prototypical member of a new class of compounds that cause paraptotic cell death via mechanisms involving eIF2alpha phosphorylation and the UPR.

Jiang W, Jiang C, Pei H, et al.
In vivo molecular mediators of cancer growth suppression and apoptosis by selenium in mammary and prostate models: lack of involvement of gadd genes.
Mol Cancer Ther. 2009; 8(3):682-91 [PubMed] Free Access to Full Article Related Publications
We used acute selenium (Se) treatments (i.e., daily single oral gavage of 2 mg Se per kilogram of body weight for 3 days) of female Sprague-Dawley rats bearing 1-methyl-1-nitrosourea-induced mammary carcinomas to increase the probability of detecting in vivo apoptosis and the associated gene/protein changes in the cancerous epithelial cells. The results show that whereas control carcinomas doubled in volume in 3 days, Se-methylselenocysteine and selenite treatments regressed approximately half of the carcinomas, accompanied by a 3- to 4-fold increase of morphologically observable apoptosis and approximately 40% inhibition of 5-bromo-2'-deoxyuridine index of the cancerous epithelial cells. The mRNA levels of growth arrest-DNA damage inducible 34 (gadd34), gadd45, and gadd153 genes were, contrary to expectation, not higher in the Se-treated carcinomas than in the gavage or diet restriction control groups. The gadd34 and gadd153 proteins were localized in the nonepithelial cells and not induced in the cancer epithelial cells of the Se-treated carcinomas. On the other hand, both Se forms decreased the expression of cyclin D1 and increased levels of P27Kip1 and c-Jun NH2-terminal kinase activation in a majority of the mammary carcinomas. Furthermore, the lack of induction of gadd genes in vivo by methylseleninic acid was confirmed in a human prostate xenograft model in athymic nude mice. In summary, these experiments showed the induction of cancer epithelial cell apoptosis and inhibition of cell proliferation by Se in vivo through the potential involvement of cyclin D1, P27Kip1, and c-Jun NH2-terminal kinase pathways. They cast doubt on the three gadd genes as mediators of Se action in vivo.

Schewe DM, Aguirre-Ghiso JA
Inhibition of eIF2alpha dephosphorylation maximizes bortezomib efficiency and eliminates quiescent multiple myeloma cells surviving proteasome inhibitor therapy.
Cancer Res. 2009; 69(4):1545-52 [PubMed] Free Access to Full Article Related Publications
The proteasome inhibitor bortezomib (Velcade) effectively eradicates multiple myeloma (MM) cells, partly by activating endoplasmic reticulum (ER) stress apoptotic signaling. However, MM recurrences in bortezomib-treated patients are invariable. We have shown that ER stress signaling can also induce growth arrest and survival in cancer cells. Thus, we hypothesized that bortezomib therapy could induce quiescence and survival of residual MM cells, contributing to disease recurrence. Here, we report that in MM cells, proteasome inhibition with MG-132 or bortezomib results in a surviving cell fraction that enters a prolonged quiescent state (G(0)-G(1) arrest). Mechanism analysis revealed that bortezomib-surviving quiescent cells attenuate eIF2alpha phosphorylation and induction of the ER stress proapoptotic gene GADD153. This occurs independently of the eIF2alpha upstream kinases PERK, GCN2, and PKR. In contrast, the prosurvival ER-chaperone BiP/Grp78 was persistently induced. The bortezomib-surviving quiescent fraction could be eradicated by a simultaneous or sequential combination therapy with salubrinal, an inhibitor of GADD34-PP1C phosphatase complex, and, in consequence, eIF2alpha dephosphorylation. This effect was mimicked by expression of a phosphorylated mimetic eIF2alpha-S51D mutant. Our data indicate that bortezomib can induce growth arrest in therapy-surviving MM cells and that attenuation of eIF2alpha phosphorylation contributes to this survival. Most importantly, this survival mechanism can be blocked by inhibiting eIF2alpha dephosphorylation. Thus, strategies that maintain eIF2alpha in a hyperphosphorylated state may be a novel therapeutic approach to maximize bortezomib-induced apoptosis and reduce residual disease and recurrences in this type of cancer.

Disclaimer: This site is for educational purposes only; it can not be used in diagnosis or treatment.

Cite this page: Cotterill SJ. PPP1R15A, Cancer Genetics Web: http://www.cancer-genetics.org/PPP1R15A.htm Accessed:

Creative Commons License
This page in Cancer Genetics Web by Simon Cotterill is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
Note: content of abstracts copyright of respective publishers - seek permission where appropriate.

 [Home]    Page last revised: 30 August, 2019     Cancer Genetics Web, Established 1999