CoChat
Sign Up
Cited by 49NF-κB Signaling PathwaysSignaling Pathways in DiseaseGlioma Diagnosis and Treatment

Tumor suppressor PDCD4 inhibits NF-κB-dependent transcription in human glioblastoma cells by direct interaction with p65

Open access
Hwang, Soon-Kyung, Baker, Alyson R., Young, Matthew R., Colburn, Nancy H.·2014·Carcinogenesis
DOI 10.1093/carcin/bgu008PMC PMC4076808
Open this paper in CoChat — free account

Abstract

PDCD4 is a tumor suppressor induced by apoptotic stimuli that regulates both translation and transcription. Previously, we showed that overexpression of PDCD4 leads to decreased anchorage-independent growth in glioblastoma (GBM)-derived cell lines and decreased tumor growth in a GBM xenograft model. In inflammatory cells, PDCD4 stimulates tumor necrosis factor-induced activation of the transcription factor NF-κB, an oncogenic driver in many cancer sites. However, the effect of PDCD4 on NF-κB transcriptional activity in most cancers including GBM is still unknown. We studied the effect of PDCD4 on NF-κB-dependent transcriptional activity in GBM by stably overexpressing PDCD4 in U251 and LN229 cells. Stable PDCD4 expression inhibits NF-κB transcriptional activation measured by a luciferase reporter. The molecular mechanism by which PDCD4 inhibits NF-κB transcriptional activation does not involve inhibited expression of NF-κB p65 or p50 proteins. PDCD4 does not inhibit pathways upstream of NF-κB including the activation of IKKα and IKKβ kinases or degradation of IκBα, events needed for nuclear transport of p65 and p50. PDCD4 overexpression does inhibit localization of p65 but not p50 in the nucleus. PDCD4 protein interacts preferentially with p65 protein as shown by co-immunoprecipitation and confocal imaging. PDCD4 overexpression inhibits the mRNA expression of two NF-κB target genes in a p65-dependent manner. These results suggest that PDCD4 can significantly inhibit NF-κB activity in GBM cells by a mechanism that involves direct or indirect protein-protein interaction independent of the expected mRNA-selective translational inhibition. These findings offer novel opportunities for NF-κB-targeted interventions to prevent or treat cancer.

AI snapshot

Written from the paper’s full text.

TL;DR

PDCD4 inhibits NF-κB-dependent transcription in human glioblastoma cells by interacting with p65 and reducing its nuclear localization, independent of PDCD4’s translation-inhibitory activity. This suppresses NF-κB target genes MMP-9 and VEGF and reduces glioblastoma cell invasion.

Key findings

  • Stable PDCD4 overexpression significantly inhibited NF-κB luciferase reporter activity by 45% in U251 cells and 30% in LN229 cells, while not inhibiting SRE- or RARE-dependent transcription.
  • PDCD4 did not change p65 or p50 protein levels, IKKα/β phosphorylation or expression, or IκBα phosphorylation/degradation; instead, it substantially reduced nuclear p65 but not nuclear p50 or p52, with small significant decreases in nuclear c-Rel and RelB only in U251 cells.
  • PDCD4 co-immunoprecipitated preferentially with p65, not with p50, c-Rel, RelB, or p52, and confocal imaging showed PDCD4–p65 colocalization almost exclusively in the cytoplasm; translation-inactive PDCD4 mutants also bound p65, reduced nuclear p65, and inhibited target gene expression.
  • PDCD4 inhibited MMP-9 mRNA by >40% in U251 cells and significantly in LN229 cells, inhibited VEGF mRNA by >40% in U251 cells, reduced MMP-9 protein in both lines and VEGF protein in U251 cells, reduced p65 binding to MMP-9 and VEGF promoters to background levels, and significantly suppressed invasion in both GBM lines.

Methods

  • Human GBM cell lines U251 and LN229 were stably transfected with human PDCD4 in pFB-Blast to generate pooled clones, with pFB-blast vector controls.
  • The study used NF-κB, AP-1, SRE, and RARE luciferase reporter assays; immunoblotting; cytosolic/nuclear fractionation; co-immunoprecipitation; confocal immunofluorescence; qRT-PCR; chromatin immunoprecipitation; and Matrigel invasion assays.
  • Statistical analysis used Student’s t-test, with data presented as mean ± SE and experiments representing at least three independent replications; significance indicated at *P < 0.05 and P < 0.01.

Limitations

  • The paper does not state explicit limitations.
  • Evident from the text: the mechanism is described as direct or indirect, and the p65-binding domain on PDCD4 and the PDCD4-binding domain on p65 remain unmapped, with the authors noting that mapping these domains “will be of interest for future studies.”
  • Evident from the text: the experimental work is limited to two human GBM cell lines with stable PDCD4 overexpression, and the biological invasion findings are from in vitro Matrigel assays rather than in vivo models.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1093/carcin/bgu008

Cites

47 of 47 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

17 of 34 cited sources checked · 12 supported · 0 flagged · accuracy not yet measured

  • Interpretationown data
    § Results

    Changes in upstream regulators of NF-κB do not contribute to the inhibition of NF-κB transactivation by PDCD4.

    “These results indicate that, in contrast to the observation in HT29 colon cancer cells (29), changes in upstream regulators of NF-κB do not contribute to the inhibition of NF-κB transactivation by PDCD4.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [29] Guo, (2011), AKT Activation by Pdcd4 Knockdown Up-Regulates Cyclin D1 Expression and Promotes Cell Proliferation, Genes Cancer source
  • Premisecitation
    § Discussion

    PDCD4 inhibits NF-κB transactivation, as observed for HT29 colon cancer cells.

    “As observed for HT29 colon cancer cells (29), PDCD4 inhibits NF-κB transactivation”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [29] Guo, (2011), AKT Activation by Pdcd4 Knockdown Up-Regulates Cyclin D1 Expression and Promotes Cell Proliferation, Genes Cancer source
  • Interpretationcitation
    § Discussion

    Transcription of genes such as cyclin D1 having NF-κB-binding sites, but not attenuated by PDCD4, may be predominantly regulated by other transcription factors or by other NF-κB proteins.

    “Transcription of genes such as cyclin D1 having NF-κB-binding sites, but not attenuated by PDCD4, may be predominantly regulated by other transcription factors as described by others (41) or by other NF-κB proteins.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [41] Zhang, (2012), PAX2 protein induces expression of cyclin D1 through activating AP-1 protein and promotes proliferation of colon cancer cells, J. Biol. Chem. source
  • Findingcitation
    § Discussion

    PDCD4 also inhibits invasion in GBM cell lines as it does in other human cancer cell lines.

    “PDCD4 also inhibits invasion in GBM cell lines as it does in other human cancer cell lines (24).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [24] Santhanam, (2010), Pdcd4 repression of lysyl oxidase inhibits hypoxia-induced breast cancer cell invasion, Oncogene source
  • Findingown data
    § Results

    PDCD4 overexpression does not change p50 protein level.

    “The level of p50 protein, the p65 dimer partner often required for NF-κB transcription factor activity, was also unchanged by PDCD4.”
    Quote in the paperNot a substantial claim
  • May combine two claims. 26
  • Classified as probably not a substantial claim. 20
  • The quote only partly states this claim. 1

  • May combine two claims.

    Premisecitation
    § Abstract

    Overexpression of PDCD4 leads to decreased anchorage-independent growth in GBM-derived cell lines and decreased tumor growth in a GBM xenograft model.

    “Previously, we showed that overexpression of PDCD4 leads to decreased anchorage-independent growth in glioblastoma (GBM)-derived cell lines and decreased tumor growth in a GBM xenograft model.”
    • Also stated in: § Introduction · plain
      “We recently reported that PDCD4 leads to decreased anchorage-independent growth in glioblastoma (GBM)-derived cell lines as well as decreased tumor growth in a GBM xenograft model (13).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [13] Gaur, (2011), Downregulation of Pdcd4 by mir-21 facilitates glioblastoma proliferation in vivo, Neuro. Oncol. source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Introduction

    PDCD4 inhibits cyclin D1 transcription in colon cancer cells by an IKK/NF-κB-dependent mechanism.

    “PDCD4 inhibits cyclin D1 transcription in colon cancer cells by an IKK/NF-κB-dependent mechanism (29).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [29] Guo, (2011), AKT Activation by Pdcd4 Knockdown Up-Regulates Cyclin D1 Expression and Promotes Cell Proliferation, Genes Cancer source

  • May combine two claims.

    Premisecitation
    § Abstract

    PDCD4 is a tumor suppressor induced by apoptotic stimuli that regulates both translation and transcription.

    “PDCD4 is a tumor suppressor induced by apoptotic stimuli that regulates both translation and transcription.”
    • Also stated in: § Introduction · plain
      “PDCD4 was first described as a protein induced by apoptotic stimuli (1) and subsequently shown to act as a tumor suppressor (2).”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [1] Shibahara, (1995), Isolation of a novel mouse gene MA-3 that is induced upon programmed cell death, Gene source
    • cites [2] Cmarik, (1999), Differentially expressed protein Pdcd4 inhibits tumor promoter-induced neoplastic transformation, Proc. Natl Acad. Sci. USA source

      The Discussion reports that Pdcd4 inhibits tumor promoter-induced neoplastic transformation and that its gene was found to be up-regulated with apoptosis in several model systems. It only proposes that Pdcd4 might regulate gene expression through transcription factors; it does not establish transcriptional regulation. The passage mentioning translation concerns an effect of antisense RNA, not a translation-regulating function of Pdcd4. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § Introduction

    PDCD4 loss is diagnostic for human cancer staging and prognostic for survival in colon, lung, liver, breast, glioma and esophageal cancers.

    “its loss is diagnostic for human cancer staging and prognostic for survival in colon, lung, liver, breast, glioma and esophageal cancers (6–11).”
    Quote in the paperNot a substantial claim1 of 6 sources checked
    • cites [6] Afonja, (2004), Induction of PDCD4 tumor suppressor gene expression by RAR agonists, antiestrogen and HER-2/neu antagonist in breast cancer cells. Evidence for a role in apoptosis, Oncogene source
    • cites [7] Chen, (2003), Loss of PDCD4 expression in human lung cancer correlates with tumour progression and prognosis, J. Pathol. source
    • cites [8] Gao, (2007), Frequent loss of PDCD4 expression in human glioma: possible role in the tumorigenesis of glioma, Oncol. Rep.

      Not checked in the free run.

    • cites [9] Hiyoshi, (2009), MicroRNA-21 regulates the proliferation and invasion in esophageal squamous cell carcinoma, Clin. Cancer Res. source
    • cites [10] Mudduluru, (2007), Loss of programmed cell death 4 expression marks adenoma-carcinoma transition, correlates inversely with phosphorylated protein kinase B, and is an independent prognostic factor in resected colorectal cancer, Cancer source

      The Multivariate Analysis section finds that PDCD4 loss predicts survival in patients with colorectal cancer, and the Correlation With Established Patient and Tumor Characteristics section links it to pT stage. The Discussion proposes PDCD4 staining as an additional tool for distinguishing normal tissue, adenomas, and carcinomas; it does not establish PDCD4 loss as a diagnostic test for cancer staging. This paper addresses colorectal cancer, while the sentence cites multiple sources for the other cancers. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [11] Zhang, (2006), Involvement of programmed cell death 4 in transforming growth factor-beta1-induced apoptosis in human hepatocellular carcinoma, Oncogene source

  • Classified as probably not a substantial claim.

    Premisecitation
    § Results

    PDCD4 localizes both to the nucleus and the cytoplasm in cancer cells.

    “PDCD4 is known to localize both to the nucleus and the cytoplasm in cancer cells (10).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [10] Mudduluru, (2007), Loss of programmed cell death 4 expression marks adenoma-carcinoma transition, correlates inversely with phosphorylated protein kinase B, and is an independent prognostic factor in resected colorectal cancer, Cancer source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Results

    PDCD4 is known to localize both to the nucleus and the cytoplasm in cancer cells.

    “PDCD4 is known to localize both to the nucleus and the cytoplasm in cancer cells (10).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [10] Mudduluru, (2007), Loss of programmed cell death 4 expression marks adenoma-carcinoma transition, correlates inversely with phosphorylated protein kinase B, and is an independent prognostic factor in resected colorectal cancer, Cancer source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § Introduction

    PDCD4 inhibits translation in an mRNA-selective way by interacting with eIF4A and inhibiting its RNA helicase activity.

    “PDCD4 inhibits translation in an mRNA-selective way by interacting with translation initiation factor eIF4A and inhibiting its RNA helicase activity (14,15).”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [14] Yang, (2004), A novel function of the MA-3 domains in transformation and translation suppressor Pdcd4 is essential for its binding to eukaryotic translation initiation factor 4A, Mol. Cell. Biol. source
    • cites [15] Yang, (2003), The transformation suppressor Pdcd4 is a novel eukaryotic translation initiation factor 4A binding protein that inhibits translation, Mol. Cell. Biol. source

      The Discussion reports that Pdcd4 binds eIF4A and inhibits its helicase activity and translation. The Results show preferential inhibition of cap-dependent over IRES-dependent translation in vivo, but both reporters are on the same mRNA; the Discussion says the mRNA targets of Pdcd4 are unknown. Thus, the paper does not establish mRNA-selective inhibition. (LLM, conf=0.86)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Discussion

    A number of NF-κB-targeting drugs have been used in clinical trials, with sometimes disappointing results.

    “A number of NF-κB-targeting drugs have been used in clinical trials, with sometimes disappointing results (45).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [45] Staudt, (2010), Oncogenic activation of NF-kappaB, Cold Spring Harb. Perspect. Biol. source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Discussion

    VEGF and MMP-9 are known to be important in invasion in the case of many human cancer cells.

    “VEGF and MMP-9 are known to be important in invasion in the case of many human cancer cells (39).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [39] Liu, (2011), Expression of VEGF and MMP-9 and MRI imaging changes in cerebral glioma, Oncol. Lett. source

      The Discussion (page unavailable) describes how VEGF and MMP-9 contribute to tumor invasion and identifies their expression as an indicator of glioma invasion. The study examines cerebral gliomas, however, and does not establish their importance across many kinds of human cancer cells. (LLM, conf=0.83)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Discussion

    A number of genes that regulate apoptosis, cell proliferation, invasion or angiogenesis are known to be NF-κB target genes in one or more models or cancer sites.

    “A number of genes that regulate apoptosis, cell proliferation, invasion or angiogenesis are known to be NF-κB target genes in one or more models or cancer sites (32).”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [32] Hayden, (2004), Signaling to NF-kappaB, Genes Dev. source

      The “TNFα: a model NF-κB stimulus” section identifies antiapoptotic genes, including cIAP1/2 and Bcl-XL, whose expression is regulated through NF-κB. The paper also links NF-κB signaling to lymphocyte proliferation, but the passages found do not identify NF-κB target genes regulating invasion or angiogenesis, or establish the full claim across cancer models or sites (searched: angiogenesis, invasion, proliferation). (LLM, conf=0.86)

      Experimental — accuracy not yet measured

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Discussion

    Other tumor suppressors among them Fbw7 and p53 have also been reported to target NF-κB.

    “It is noteworthy that other tumor suppressors among them Fbw7 (43) and p53 have also been reported to target NF-κB (44).”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [43] Arabi, (2012), Proteomic screen reveals Fbw7 as a modulator of the NF-κB pathway, Nat. Commun. source
    • cites [44] Ghose, (2011), Regulation of miR-146a by RelA/NFkB and p53 in STHdh(Q111)/Hdh(Q111) cells, a cell model of Huntington’s disease, PLoS One source

  • May combine two claims.

    Findingown data
    § Results

    Nuclear c-Rel and RelB showed small but significant decreases in U251 but not in LN229.

    “Nuclear c-Rel and RelB showed small but significant decreases in U251 but not in LN229.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Results

    PDCD4 does not inhibit phosphorylation of IKKα/β or total expression levels of IKKα and IKKβ.

    “As shown in Figure 2c and d, PDCD4 failed to inhibit phosphorylation of IKKα/β or total expression levels of IKKα and IKKβ.”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data
    § Abstract

    PDCD4 overexpression inhibits the mRNA expression of the NF-κB target genes MMP-9 and VEGF in a p65-dependent manner.

    “PDCD4 overexpression inhibits the mRNA expression of two NF-κB target genes in a p65-dependent manner.”
    • Also stated in: § Introduction · plain
      “NF-κB target genes matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) are identified as being PDCD4 regulated.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results

    Protein expression was unchanged except for CIAP-1, which decreased with PDCD4 overexpression.

    “Protein expression was also unchanged except for that of CIAP-1, which decreased with PDCD4 overexpression (Figure 5b).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Results

    PDCD4 does not increase IκBα protein expression or decrease phosphorylation of IκBα at Ser-32 or Ser-36.

    “PDCD4 does not increase IκBα protein expression or decrease phosphorylation of IκBα at Ser-32 or Ser-36 (Figure 2e).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results

    In U251 PDCD4-overexpressing cells, PDCD4 signal is distributed in both cytoplasm and nuclei, whereas p65 signal is mainly localized to the cytoplasm.

    “Figure 4g depicts the immunofluorescence signal for PDCD4 (red), which was distributed in both the cytoplasm and nuclei in overexpressing PDCD4 cells, whereas the signal for p65 (green) was mainly localized to the cytoplasm.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results

    p65 binds to endogenous MMP-9, VEGF, cyclin D1 and CIAP-1 gene promoters, with substantially greater binding seen for MMP-9 and VEGF promoters.

    “As seen in Figure 5g, p65 binds to endogenous MMP-9, VEGF, cyclin D1 and CIAP-1 gene promoters with substantially greater binding seen for MMP-9 and VEGF promoters.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results

    Endogenous p65 coprecipitates with PDCD4 in PDCD4-overexpressing cells, whereas IgG immunoprecipitations did not coprecipitate p65.

    “Figure 4a and b shows that endogenous p65 coprecipitates with PDCD4 in PDCD4-overexpressing cells, whereas IgG immunoprecipitations did not coprecipitate p65.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results

    PDCD4 did not inhibit SRE or RARE dependent transcription.

    “However, PDCD4 did not inhibit SRE or RARE dependent transcription (Figure 1c and d).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Discussion

    mRNA and protein levels of both MMP-9 and VEGF are downregulated by PDCD4 in GBM cells.

    “mRNA and protein levels of both are downregulated by PDCD4 in GBM cells.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Findingnone given
    § Discussion

    The PDCD4-binding domain on p65 appears not to be shared by c-Rel or RelB.

    “Of note is the observation that the PDCD4-binding domain on p65 appears not to be shared by c-Rel or RelB.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Discussion

    PDCD4 substantially suppresses the localization of p65 but not p50, c-Rel, RelB or p52 in the nucleus.

    “Instead, PDCD4 substantially suppresses the localization of p65 but not p50, c-Rel, RelB or p52 in the nucleus.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisenone given
    § Abstract

    The effect of PDCD4 on NF-κB transcriptional activity in most cancers including GBM is still unknown.

    “However, the effect of PDCD4 on NF-κB transcriptional activity in most cancers including GBM is still unknown.”
    • Also stated in: § Introduction · plain
      “Whether PDCD4 inhibits NF-κB transcriptional activity in other cancer sites and cells is still unknown.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data
    § Results

    Overexpressing PDCD4 without MG-132 did not produce an increase in IκBα of a magnitude similar to that seen in vector control cells with proteasome inhibitor, excluding the possibility that PDCD4 mimics the proteasome inhibitor by preventing degradation of IκBα.

    “Overexpressing PDCD4 without MG-132 did not produce an increase in IκBα of a magnitude similar to that seen in vector control cells with proteasome inhibitor; this excludes the possibility that PDCD4 mimics the proteasome inhibitor by preventing degradation of IκBα.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given
    § Materials and methods

    All experiments represent at least three independent replications.

    “All experiments represent at least there independent replications.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § Introduction

    As MMP-9 and VEGF are oncogenic mediators of invasion and angiogenesis, their suppressed expression may contribute to PDCD4 suppressed tumor growth and invasion.

    “As these proteins are oncogenic mediators of invasion and angiogenesis, their suppressed expression may contribute to PDCD4 suppressed tumor growth and invasion.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: MMP-9 and VEGF are oncogenic mediators of invasion and angiogenesis.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation
    § Introduction

    PDCD4 does not inhibit NF-κB in mouse JB6 cells where it inhibits AP-1 transactivation and transformation.

    “PDCD4 does not inhibit NF-κB in mouse JB6 cells where it inhibits AP-1 transactivation and transformation (26).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [26] Yang, (2001), A novel transformation suppressor, Pdcd4, inhibits AP-1 transactivation but not NF-kappaB or ODC transactivation, Oncogene source

  • May combine two claims.

    Interpretationown data
    § Results

    PDCD4 interacts with p65, either directly or through a third partner, in the cytoplasm, thereby inhibiting net nuclear translocation of p65.

    “These findings suggest that PDCD4 interacts with p65, either directly or through a third partner, in the cytoplasm thus inhibiting net nuclear translocation (involving import or export) of p65.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data
    § Results

    PDCD4 causes relatively specific inhibition of NF-κB in addition to AP-1-dependent transcriptional activity in GBM cells.

    “These findings indicate relatively specific inhibition of NF-κB in addition to AP-1-dependent transcriptional activity by PDCD4 in GBM cells.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data
    § Summary

    PDCD4 inhibits NF-κB by a novel mechanism that is functionally significant.

    “We here show that PDCD4 inhibits NF-κB by a novel mechanism that is functionally significant.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § Discussion

    PDCD4 directly interacts with the helix-loop-helix DNA-binding domain of Twist1 to inhibit its binding to the promoter of Y-box-binding protein (YB-1) to consequently downregulate YB-1 mRNA expression in prostate cancer cells.

    “PDCD4 directly interacts with the helix-loop-helix DNA-binding domain of Twist1 to inhibit its binding to the promoter of Y-box-binding protein (YB-1) to consequently downregulate YB-1 mRNA expression in prostate cancer cells (38).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [38] Shiota, (2009), Programmed cell death protein 4 down-regulates Y-box binding protein-1 expression via a direct interaction with Twist1 to suppress cancer cell growth, Cancer Res. source

  • May combine two claims.

    Interpretationown data
    § Discussion

    The PDCD4-regulated availability of nuclear p65 appears to be limiting for mRNA expression of invasion-inducing NF-κB target genes MMP-9 and VEGF but not for cyclin D1 and CIAP-1.

    “The PDCD4-regulated availability of nuclear p65 appears to be limiting for mRNA expression of invasion-inducing NF-κB target genes MMP-9 and VEGF but not for cyclin D1 and CIAP-1.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § Discussion

    PDCD4 knockdown stimulated translation of p53 and consequently stimulated transcription of p53 target genes such as p21 in HeLa cells.

    “Wedeken and coworkers have demonstrated that PDCD4 knockdown stimulated translation of p53 (21) and consequently stimulated transcription of p53 target genes such as p21 in HeLa cells (36).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [21] Wedeken, (2011), Tumor suppressor protein Pdcd4 inhibits translation of p53 mRNA, J. Biol. Chem. source
    • cites [36] Bitomsky, (2008), siRNA-mediated knockdown of Pdcd4 expression causes upregulation of p21(Waf1/Cip1) expression, Oncogene source

  • May combine two claims.

    Premisecitation
    § Discussion

    Both MMP-9 and VEGF are overexpressed in GBM tissues that also show overactivated NF-κB.

    “Both MMP-9 and VEGF are overexpressed in GBM tissues that also show overactivated NF-κB (40).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [40] Zanotto-Filho, (2011), NFκB inhibitors induce cell death in glioblastomas, Biochem. Pharmacol. source

  • May combine two claims.

    Interpretationown data
    § Discussion

    This inhibition of nuclear transport occurs through interaction of PDCD4 with p65 but minimally with other NF-κB proteins.

    “This inhibition of nuclear transport occurs through interaction of PDCD4 with p65 but minimally with other NF-κB proteins as seen through co-immunoprecipitation using antibody to either PDCD4 or tagged p65.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Discussion

    Apoptosis inhibitor XIAP, but not CIAP-1, has been found by Liwak et al. to show PDCD4-regulated translation via internal ribosome entry sites in HEK 293 cells.

    “Apoptosis inhibitor XIAP, but not CIAP-1, has been found by Liwak et al. (22) to show PDCD4-regulated translation via internal ribosome entry sites in HEK 293 cells.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [22] Liwak, (2012), Tumor suppressor PDCD4 represses internal ribosome entry site-mediated translation of antiapoptotic proteins and is regulated by S6 kinase 2, Mol. Cell. Biol. source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning
    § Discussion

    The lack of PDCD4 binding to p50 is consistent with the uninhibited nuclear localization of p50 if such interaction with NF-κB proteins produces sequestration in the cytoplasm.

    “Moreover, the lack of PDCD4 binding to p50 is consistent with the uninhibited nuclear localization of p50 if such interaction with NF-κB proteins produces sequestration in the cytoplasm.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Discussion

    Cyclin D1 is translationally regulated in some models.

    “Cyclin D1 is translationally regulated in some models (42).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [42] Rosenwald, (1993), Elevated levels of cyclin D1 protein in response to increased expression of eukaryotic initiation factor 4E, Mol. Cell. Biol. source

  • May combine two claims.

    Interpretationown data
    § Discussion

    Cyclin D1 and CIAP-1 are targeted at the protein expression level and their downregulation might contribute, along with that of MMP-9 and VEGF, to the tumor suppressing activity of PDCD4.

    “The latter two, however, are targeted at the protein expression level and their downregulation might therefore contribute, along with that of MMP-9 and VEGF, to the tumor suppressing activity of PDCD4.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Discussion

    PDCD4 regulates translation of two transcription factors, namely p53 and c-myb.

    “PDCD4 regulates translation of two transcription factors, namely p53 and c-myb (20,21).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [20] Singh, (2011), Pdcd4 directly binds the coding region of c-myb mRNA and suppresses its translation, Oncogene source
    • cites [21] Wedeken, (2011), Tumor suppressor protein Pdcd4 inhibits translation of p53 mRNA, J. Biol. Chem. source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Discussion

    In the case of Twist1, unlike p65, the functionally significant binding to PDCD4 occurs in the nucleus.

    “In the case of Twist1, unlike p65, the functionally significant binding to PDCD4 occurs in the nucleus.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [38] Shiota, (2009), Programmed cell death protein 4 down-regulates Y-box binding protein-1 expression via a direct interaction with Twist1 to suppress cancer cell growth, Cancer Res. source
42 of 42

  • The paper relies on this without support.

    In gliomas, NF-κB is constitutively activated, the levels of NF-κB-regulated genes are elevated, and these circumstances are inversely correlated with patient prognosis.

    “In gliomas, NF-κB is constitutively activated, the levels of NF-κB-regulated genes are elevated, and these circumstances are inversely correlated with patient prognosis.”

  • The paper relies on this without support.

    NF-κB acts as an oncogenic driver in many cancer sites.

    “The transcription factor NF-κB acts as an oncogenic driver in many cancer sites.”

  • The paper relies on this without support.

    MMP-9 and VEGF are oncogenic mediators of invasion and angiogenesis.

    “As these proteins are oncogenic mediators of invasion and angiogenesis”
3 of 3

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • PDCD4 inhibits NF-κB-dependent transcription by directly interacting with the p65 subunit in human glioma cells.

    “Baker et al. reported that PDCD4 inhibits nuclear factor-kappaB (NF-κB)-dependent transcription by directly interacting with the p65 subunit of the factor in human glioma cells [40].”

    From Control Mechanisms of the Tumor Suppressor PDCD4: Expression and Functions (2019) · cites this paper as [40]

    The Results report that PDCD4 inhibits NF-κB transcriptional activity in two human glioblastoma cell lines and that PDCD4 and p65 co-immunoprecipitate. However, the Abstract and Discussion qualify the interaction as potentially direct or indirect, so the claim's unqualified assertion of direct interaction overstates the evidence. (LLM, conf=0.84)

    Experimental — accuracy not yet measured

Cites

Flagged first, then by citations

Cited by

Sorted by citations

Related

Authors
Hwang, S.-K., Baker, A. R., Young, M. R., & Colburn, N. H.
Affiliations
Frederick National Laboratory for Cancer Research (US)
Corresponding author
Hwang, Soon-Kyung
ORCID
Young, Matthew R.
Venue
Carcinogenesis
Publisher
Oxford University Press (OUP)
Published
2014-01-11
Volume
35
Issue
7
Pages
1469-1480
ISSN
  • 0143-3334 (ISSN-L)
  • 1460-2180
DOI
10.1093/carcin/bgu008
PMC
PMC4076808
OpenAlex
W2328415948
Semantic Scholar
c69a72c5d8ee567cdb4ef95d1ffa5d2badc1967f
Cited by
49
References
46
Citations by year
2026: 1 · 2025: 3 · 2024: 1 · 2023: 1 · 2022: 4 · 2021: 3 · 2020: 11 · 2019: 2 · 2018: 6 · 2017: 3 · 2016: 8 · 2015: 4 · 2014: 2
FWCI
1.65
Type
journal article
Language
en
Open access
Locations
  • Carcinogenesis (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (submittedVersion)
Funders
  • National Institutes of Health
  • National Cancer Institute (ZIABC010026)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cancer Research › NF-κB Signaling Pathways
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Signaling Pathways in Disease
  • Health Sciences › Medicine › Genetics › Glioma Diagnosis and Treatment
Keywords
PDCD4, tumor suppressor, NF-κB, NF-κB p65, glioblastoma, transcriptional repression, protein-protein interaction, NF-κB target genes, IKK activation, IκBα degradation
MeSH terms
Cell Movement, Glioblastoma, Humans, RNA, Messenger, Transcription, Genetic, Tumor Cells, Cultured, Blotting, Western, Gene Expression Regulation, Neoplastic, RNA-Binding Proteins, Apoptosis, Reverse Transcriptase Polymerase Chain Reaction, Chromatin Immunoprecipitation, Immunoprecipitation, Cell Proliferation, Apoptosis Regulatory Proteins, Transcription Factor RelA, NF-kappa B p50 Subunit, Real-Time Polymerase Chain Reaction

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-21.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-21.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review