The DOI matches its Crossref record; 44 of the 45 references it cites were found in a registry or an index; 5 of the 26 sources its claims cite were checked for support.
MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells
Open accessPublished version of a preprint
Abstract
MicroRNA dysregulation is observed in different types of cancer. MiR-21 up-regulation has been reported for the majority of cancers profiled to date; however, knowledge is limited on the mechanism of action of miR-21, including identification of functionally important targets that contribute to its proproliferative and antiapoptotic actions. In this study, we show for the first time that miR-21 targets multiple important components of the p53, transforming growth factor-β (TGF-β), and mitochondrial apoptosis tumor-suppressive pathways. Down-regulation of miR-21 in glioblastoma cells leads to derepression of these pathways, causing repression of growth, increased apoptosis, and cell cycle arrest. These phenotypes are dependent on two of the miR-21 targets validated in this study, HNRPK and TAp63. These findings establish miR-21 as an important oncogene that targets a network of p53, TGF-β, and mitochondrial apoptosis tumor suppressor genes in glioblastoma cells. [Cancer Res 2008;68(19):8164–72]
Overview
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Written from the paper’s full text.
TL;DR
In glioblastoma cells, miR-21 directly targets and represses a network of p53, TGF-β, and mitochondrial apoptosis tumor-suppressive genes. Knockdown derepresses these pathways, increasing apoptosis and cell-cycle arrest and suppressing growth, with HNRPK and TAp63 required for key phenotypes.
Key findings
- miR-21 knockdown in U251 cells caused 2- to 16-fold increases in mRNA levels of major p53/TGF-β/apoptotic pathway components; protein levels of examined targets increased 2- to 3-fold.
- Luciferase assays validated direct targeting of JMY, TGFBR2, TGFBR3, HNRPK, TP73L (TAp63), APAF1, BMPR2, TOPORS, DAXX, TP53BP2, and PPIF; IGFBP3 did not change. The positive anti-miR-21 reporter showed a 70% decrease, and PDCD4 showed a ~30% decrease.
- LNA-miR-21 increased Annexin V 1.5- to 2-fold at 24/48 h; siRNA against TAp63 or HNRPK reduced Annexin V induction by ~25%. miR-21 overexpression blocked doxorubicin-induced caspase-3/7 activation in U251 and U87 cells.
- Knockdown suppressed growth over 4 days (most significant on day 3) and increased G0-G1 arrest in U251 by 21% with nocodazole and 25% with doxorubicin; siRNA-HNRPK/TAp63 produced a 2-fold decrease in G0-G1 arrest.
Methods
- U251, U87, and HeLa cells were used; miR-21 was down-regulated with LNA-miR-21 or 2′-O-me-miR-21, and overexpressed in HeLa cells via lentivirus. Assays included real-time PCR, immunoblotting, dual luciferase reporters containing 60-bp 3′UTR sequences, CellTiter Glo growth assays, Annexin V and caspase-3/7 apoptosis assays, and PI cell-cycle analysis after nocodazole/doxorubicin synchronization.
- Target prediction used TargetScan 3.1 (1,398 human miR-21 targets including duplicates), and network analysis used Ingenuity Pathway Analysis 3.0, yielding 765 network-eligible genes after filtering. Statistics used ANOVA or Student’s t test, with significance at P < 0.05 or P < 0.01; growth and apoptosis results represent means of three separate experiments.
Limitations
- Stated: knockdown of HNRPK and TAp63 did not completely rescue the proapoptotic and cell-cycle arrest phenotypes, suggesting other critical miR-21 targets are involved.
- Evident: all functional experiments were performed in cell lines (U251, U87, HeLa), with no in vivo tumor model or patient tumor samples in this paper.
- Evident: luciferase validation used 60-bp 3′UTR fragments containing predicted sites rather than full 3′UTRs, and only selected predicted targets were validated.
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Claims the paper makes
34 Own result · 27 Own interpretation · 13 No full text of the sources · 5 No basis given · 4 Not checked yet · 2 Partly supported · 1 Supported · 1 Supported so far · accuracy not yet measured
The cited sources support only part of this claim — read each source’s verdict below.
In the paper
“These data are also consistent with findings in glioblastomas that significant effects of miRNAs occur indirectly rather than by direct targeting (24,43).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
What the sources say
- Could not verifycites [24] Li Q, Wang X, Wu X, et al. Daxx Cooperates with the Axin/HIPK2/p53 complex to induce cell death. Cancer Res 2007; 67: 66–74. sourceExperimental — accuracy not yet measured
The Discussion passages describe Daxx, Axin, p53 and apoptosis, including experiments using siRNA against Axin. Searches for glioblastoma, miRNAs and indirect versus direct targeting found no passage in our copy addressing the attributed finding. The paper’s use of siRNA does not establish a claim about miRNA effects in glioblastomas. (LLM, conf=0.76)
- Partly supportedcites [43] Johnson CD, Esquela-Kerscher A, Stefani G, et al. The let-7 MicroRNA represses cell proliferation pathways in human cells. Cancer Res 2007; 67: 7713–22. sourceExperimental — accuracy not yet measured
The Discussion (page unavailable) says that only 25 of 176 early repressed genes were likely direct let-7 targets, and the cell-cycle section describes indirect changes downstream of direct targets. But the experiments used liver and lung cancer cell lines, not glioblastomas, so the glioblastoma-specific claim is not supported by this paper. (LLM, conf=0.85)
plaindirect- Asserted: passes — The authors put it forward as true.
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- Could not verify
Every source the paper cites for this claim was checked and supports it.
In the paper
“Interestingly, a transcriptional target of the functional convergence of these pathways is SERPINB5, the transcript most highly up-regulated in response to miR-21 knockdown (Fig. 2A; ref. 42).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
What the sources say
- Supportedcites [42] Wang SE, Narasanna A, Whitell CW, Wu FY, Friedman DB, Arteaga CL. Convergence of p53 and transforming growth factor β (TGFβ) signaling on activating expression of the tumor suppressor gene maspin in mammary epithelial cells. J Biol Chem 2007; 282: 5661–9. source
The paper states that TGFβ induces maspin expression through Smads and that p53 binding to the maspin promoter is required for TGFβ-induced transcription. Its discussion explicitly describes maspin as an example of gene-expression co-regulation by the p53 and TGFβ pathways. The citation supports the pathway claim; the sentence attributes the miR-21 knockdown result to Fig. 2A, not to this source. (LLM, conf=0.93)
plaindirect- Asserted: passes — The authors put it forward as true.
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- Supported
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Down-regulation of miR-21 in glioblastoma cells leads to derepression of these pathways, causing repression of growth, increased apoptosis, and cell cycle arrest.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Abstract
plaindirect- Asserted: passes — The authors put it forward as true.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Upon down-regulation of miR-21 with LNA, we observed significant increases ranging from 2-fold to 16-fold in the levels of major components of the p53/TGF-h/apoptotic pathways, including many of the predicted targets (Fig. 2).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > MiR-21 predicted targets form network of interactions.
plaindirect- Asserted: passes — The authors put it forward as true.
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None of the sources cited for this claim have been checked yet.
In the paper
“p53 pathway predicted targets included the tumor-suppressive homologue of p53, TP73L (TAp63), and activating cofactors of p53, such as JMY, TOPORS, HNRPK, and TP53BP2 (19, 21-26).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > MiR-21 predicted targets form network of interactions.
plaincorrelational- Asserted: passes — The authors put it forward as true.
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None of the sources cited for this claim have been checked yet.
In the paper
“In addition, PDCD4, which is involved in mediating TGFh-induced apoptosis, increased f8-fold (35).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > MiR-21 predicted targets form network of interactions.
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Several of the genes involved in mitochondrial apoptosis were also up-regulated in response to miR-21 down-regulation, including APAF1, PPIF, and caspase-3 (CASP3).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > MiR-21 predicted targets form network of interactions.
plaindirect- Asserted: passes — The authors put it forward as true.
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The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Additionally, we observed increases in several transactivation targets of p53, such as IGFBP3, TNSFRSF10B, NOXA, p21 (CDKN1A), and GADD45A, which are expected due to the increase of p53 and its homologues (Fig. 2A; refs.19,34).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > MiR-21 predicted targets form network of interactions.
plaindirect- Asserted: passes — The authors put it forward as true.
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- Load-bearing: passes — The paper’s conclusions depend on it.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The p53 pathway was derepressed to a great extent in response to miR-21 knockdown.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > MiR-21 predicted targets form network of interactions.
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“These phenotypes are dependent on two of the miR-21 targets validated in this study, HNRPK and TAp63.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Abstract
plaindirect- Asserted: passes — The authors put it forward as true.
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- Load-bearing: passes — The paper’s conclusions depend on it.
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- Probably not a substantial claim. 6
- It may state two separate claims as one. 21
The cited sources support only part of this claim — read each source’s verdict below.
In the paper
“Three miR-21 targets have, thus far, been described: phosphatase and tensin homologue (PTEN), programmed cell death 4 (PDCD4) and Tropomyosin 1 (TPM1; refs.10,[14][15][16].”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Introduction
What the sources say
- Partly supportedcites [10] Meng F, Henson R, Lang M, et al. Involvement of human micro-RNA in growth and response to chemotherapy in human cholangiocarcinoma cell lines. Gastroenterology 2006; 130: 2113–29. sourceExperimental — accuracy not yet measured
The section “miR-21 Directly Alters PTEN Expression” (page unavailable) reports that miR-21 directly modulates expression through PTEN’s 3′-UTR, supporting PTEN as a target. Searches for PDCD4 and TPM1 found no passages in our copy describing either as a miR-21 target, so this source does not support those two parts of the list. (LLM, conf=0.88)
- Not checked — no full text of the sourcecites [14] Asangani IA, Rasheed SAK, Nikolova DA, et al. MicroRNA-21 (miR-21) post-transcriptionally down-regulates tumor suppressor Pdcd4 and stimulates invasion, intravasation and metastasis in colorectal cancer. Oncogene 2007; 27: 2128–36. source
- Not checked — no full text of the sourcecites [15] Frankel LB, Christoffersen NR, Jacobsen A, Lindow M, Krogh A, Lund AH. Programmed cell death 4 (PDCD4) is an important functional target of the microRNA miR-21 in breast cancer cells. J Biol Chem 2008; 283: 1026–33. source
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim.
- Partly supported
The sources with a verdict support this claim; the rest weren’t checked yet, have no full text we could read, or their verdicts aren’t rated yet.
In the paper
“TAp63 is a homologue of p53 and is known to mediate both cell cycle arrest and apoptosis (19,38).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
What the sources say
- Not checked — no full text of the sourcecites [19] Stiewe T. The p53 family in differentiation and tumorigenesis. Nat Rev Cancer 2007; 7: 165–7. source
- Supportedcites [38] Gressner O, Schilling T, Lorenz K, et al. TAp63α induces apoptosis by activating signaling via death receptors and mitochondria. EMBO J 2005; 24: 2458–71. source
The Introduction identifies TAp63 as a p53-like protein in the p53 family. In ‘Induction of apoptosis in TAp63α-inducible p53-negative cells,’ the authors report both G1 cell-cycle arrest and apoptosis after inducing TAp63α. (LLM, conf=0.93)
boosteddirect- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. It may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“APAF1 and PPIF are both predicted targets of miR-21 (Fig. 2C).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > MiR-21 predicted targets form network of interactions.
plaincorrelational- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“We also observed increases in proteins, such as p53, DNA damage-activated p53 (Ser 15 ), and p21, which are not targets but are indirectly negatively regulated by miR-21 (Fig. 2).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > MiR-21 target validation.
plaindirect- Asserted: passes — The authors put it forward as true.
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- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
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It may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“For both U251 and U87 cell lines, cells expressing the scrambled control showed a predicted dose-dependent increase in caspase-3/ caspase-7 activity, whereas the cells expressing miR-21 did not respond to the drug treatment even at higher doses (Fig. 5C).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > MiR-21 target validation.
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
- Rests on an assumption: The p53 pathway is functional and can mediate apoptosis in the U251 and U87 cell lines used.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“We have shown that miR-21 regulates sets of genes, and the regulation is direct through targeting of certain transcripts, and in other cases, the effects are indirect.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
boosteddirect- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“In addition, miR-21 down-regulation significantly represses growth and leads to cell cycle arrest at G 0 -G 1 , which can be explained by the up-regulation of p21 (Figs.2A and 4A), a protein that is known to regulate cell cycle checkpoints in response to its transactivation by p53.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
plaindirect- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This retarded growth continued throughout the 4 days with the most significant difference observed on day 3.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > MiR-21 target validation.
plaindirect- Asserted: passes — The authors put it forward as true.
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- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“High levels of miR-21 were first reported in glioblastoma tumors and cell lines (6).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Introduction
What the sources say
- Not checked — no full text of the sourcecites [6] Chan JA, Krichevsky AM, Kosik KS. MicroRNA-21 Is an antiapoptotic factor in human glioblastoma cells. Cancer Res 2005; 65: 6029–33. source
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“In the same study, inhibition of miR-21 by LNA or 2 ¶O-Me-miR-21 led to increased caspase-dependent apoptosis, suggesting that miR-21 could be acting as an oncogene to inhibit apoptosis in glioblastoma cells (6).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Introduction
What the sources say
- Not checked — no full text of the sourcecites [6] Chan JA, Krichevsky AM, Kosik KS. MicroRNA-21 Is an antiapoptotic factor in human glioblastoma cells. Cancer Res 2005; 65: 6029–33. source
hedgeddirect- Asserted: passes — The authors put it forward as true.
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- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“A subset of the derepressed transcripts, APAF1, BMPR2, PDCD4, and p21 were reported to be up-regulated in MCF-7 breast cancer cells with LNA-miR-21 treatment (15).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > MiR-21 predicted targets form network of interactions.
What the sources say
- Not checked — no full text of the sourcecites [15] Frankel LB, Christoffersen NR, Jacobsen A, Lindow M, Krogh A, Lund AH. Programmed cell death 4 (PDCD4) is an important functional target of the microRNA miR-21 in breast cancer cells. J Biol Chem 2008; 283: 1026–33. source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“The majority of these profiling studies have reported increased levels of miR-21 in most human cancers (6,(8)(9)(10).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Introduction
What the sources say
- Not checked — no full text of the sourcecites [6] Chan JA, Krichevsky AM, Kosik KS. MicroRNA-21 Is an antiapoptotic factor in human glioblastoma cells. Cancer Res 2005; 65: 6029–33. source
- Not checked — no full text of the sourcecites [8] Volinia S, Calin GA, Liu C-G, et al. A microRNA expression signature of human solid tumors defines cancer gene targets. Proc Natl Acad Sci U S A 2006; 103: 2257–61. source
- Not checked — no full text of the sourcecites [9] Iorio MV, Ferracin M, Liu C-G, et al. MicroRNA gene expression deregulation in human breast cancer. Cancer Res 2005; 65: 7065–70. source
plaincorrelational- Asserted: passes — The authors put it forward as true.
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- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“DAXX, which can stabilize p53 in addition to mediating TGF-h apoptosis, plays a role in both pathways and, therefore, may be a key target in disrupting crosstalk between the two pathways (Supplementary Fig. S3).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
hedgedconditional- Asserted: passes — The authors put it forward as true.
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- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“MiR-21 repressed p53-mediated apoptosis in response to chemotherapeutic (doxorubicin)-induced DNA damage, therefore contributing to drug resistance in glioblastoma cells.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
- Rests on an assumption: The p53 pathway is functional and can mediate apoptosis in the U251 and U87 cell lines used.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This result indicates that miR-21 up-regulation in cancer cells is sufficient to inhibit p53-mediated apoptosis, thus protecting the cells from p53-mediated apoptosis in response to DNA damage induced by a chemotherapeutic agent.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > MiR-21 target validation.
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
- Rests on an assumption: The p53 pathway is functional and can mediate apoptosis in the U251 and U87 cell lines used.
In the paper
“In accordance, we observe a significant increase in the protein levels of p53 (Ser 15 ; Fig. 4A), which occurs in response to DNA damage and can mediate cell cycle arrest at G 0 -G 1 by transactivation of p21 (19).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
What the sources say
- Not checked — no full text of the sourcecites [19] Stiewe T. The p53 family in differentiation and tumorigenesis. Nat Rev Cancer 2007; 7: 165–7. source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. It may state two separate claims as one.
In the paper
“This finding is in agreement with limited data from other laboratories that suggests that many miRNAs have evolved to regulate multiple components of certain pathways, thus mediating a more effective negative regulation on those pathways (33).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
What the sources say
- Not checked — no full text of the sourcecites [33] Esau C, Davis S, Murray SF, et al. miR-122 regulation of lipid metabolism revealed by in vivo antisense targeting. Cell Metabol 2006; 3: 87–98. source
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A claim is checked only against the cited paper’s full text, never its abstract, and none is available for its sources.
In the paper
“The miR-21 targets we identified included p53 homologue, p63, p53 activators JMY, TOPORS, TP53BP2, DAXX, and HNRPK, which can stabilize p53 protein levels by interfering with MDM2 and/or act as p53 transcriptional cofactors, assisting p53 in transactivating genes that can induce apoptosis and growth arrest (21)(22)(23)(24)(25)(26).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
What the sources say
- Not checked — no full text of the sourcecites [21] Coutts AS, La Thangue NB. The p53 response: emerging levels of co-factor complexity. Biochem Biophys Res Commun 2005; 331: 778–85. source
- Not checked — no full text of the sourcecites [22] Moumen A, Masterson P, O'Connor MJ, Jackson SP. hnRNP K: an HDM2 target and transcriptional coactivator of p53 in response to DNA damage. Cell 2005; 123: 1065–78. source
- Not checked — no full text of the sourcecites [23] Samuels-Lev Y, O'Connor DJ, Bergamaschi D, et al. ASPP proteins specifically stimulate the apoptotic function of p53. Mol Cell 2001; 8: 781–94. source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Our approach links putative targets around a function and succeeds in identifying not only multiple targets but uncover an entire network under miRNA control.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
plaincorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“MiR-21 suppression of the p53 response may take place in most cancers where miR-21 is up-regulated, and this oncogenic mechanism may be even more significant contributor to malignancy in tumors with wild-type p53.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This resistance may be partly due to the negative regulation of multiple components of the pathway of miR-21, including the indirect regulation of TGFB1/2 and the direct targeting of the receptors TGFBR2/3 and the apoptotic mediator DAXX.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“These broad effects enable miR-21 to act as a key oncogene modulating cell growth, desensitizing cells to apoptosis and cell cycle arrest (Supplementary Fig. S3).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Due to the functional relationship among miR-21 targets, changes in the level of miR-21 is likely to dampen the robustness of a highly interconnected tumor-suppressive network and result in global regulation or dysregulation of the network functions.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
hedgedconditional- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The effects we describe when we knockdown miR-21 suggest that miR-21 lies embedded in a nexus of tumor suppression genes and has multiple specific targets in the network that lead to the observed phenotypes.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
hedgeddirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“Cancer cells therefore only survive if the apoptotic response is dampened or disrupted, cell cycle checkpoints are evaded, and unrestricted cell proliferation occurs (44).”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
What the sources say
- Not checked — no full text of the sourcecites [44] Hanahan D, Weinberg RA. The hallmarks of cancer. Cell 2000; 100: 57–70. source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: unclear — It is unclear whether the paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
The paper relies on this without support.
The mechanism of action of miR-21, including its functionally important targets, is largely unknown.
“Although miR-21 is emerging as a novel oncogene, its mechanism of action is largely unknown.”
“knowledge is limited on the mechanism of action of miR-21, including identification of functionally important targets that contribute to its proproliferative and antiapoptotic actions.”
The paper relies on this without support.
The known miR-21 targets PTEN, PDCD4, and TPM1 do not fully explain the antiapoptotic function of miR-21 in glioblastomas and other cancers.
“However, these targets do not fully elucidate the antiapoptotic function of miR-21 in glioblastomas and other types of cancer.”
The paper relies on this without support.
Knowledge on the contribution of PDCD4 and TPM1 to the malignant phenotype of glioblastomas is limited.
“On the other hand, knowledge is limited on the contribution of PDCD4 and TPM1 to the malignant phenotype of glioblastomas.”
The paper relies on this without support.
U251 and U87 cell lines are representative models of glioblastoma for generalizing miR-21 function to glioblastoma.
“We were able to show these effects in two established glioblastoma cells lines, U251 and U87.”
“These results suggest that miR-21 plays an essential role in the proliferative capacity of glioblastoma cells.”
The paper relies on this without support.
The siRNA-mediated knockdown of HNRPK and TAp63 is specific and does not produce off-target effects that confound the cell cycle and apoptosis results.
“In the presence of siRNA-HNRPK and siRNA-TAp63, we observed a 2-fold decrease in the proportion of cells arrested in G 0 -G 1 in response to miR-21 down-regulation.”
“we used the same siRNAs previously tested in the Annexin V assays.”
The paper relies on this without support.
The p53 pathway is functional and can mediate apoptosis in the U251 and U87 cell lines used.
“For both U251 and U87 cell lines, cells expressing the scrambled control showed a predicted dose-dependent increase in caspase-3/ caspase-7 activity, whereas the cells expressing miR-21 did not respond to the drug treatment even at higher doses (Fig. 5C).”
“This result indicates that miR-21 up-regulation in cancer cells is sufficient to inhibit p53-mediated apoptosis, thus protecting the cells from p53-mediated apoptosis in response to DNA damage induced by a chemotherapeutic agent.”
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?
The source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“miR-21 targets several genes such as PDCD4, TIMP3, and RECK, which are key regulators of apoptotic and metastatic pathways (17–23).”
From Potential Therapeutic Effects of Exosomes Packed With a miR-21-Sponge Construct in a Rat Model of Glioblastoma (2019) · cites this paper as [19]
Experimental — accuracy not yet measuredThe source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“miR-21 is a well-known miRNA, found to be overexpressed in almost all cancer types, where its upregulation promotes cell proliferation, invasion, and metastatic behavior.”
From Potential Therapeutic Effects of Exosomes Packed With a miR-21-Sponge Construct in a Rat Model of Glioblastoma (2019) · cites this paper as [19]
Experimental — accuracy not yet measuredThe source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“Our data on the effects of miR-21 enriched exosomes is in agreement with the previous reports demonstrating that overexpressed miR-21 in cell lines can increase the proliferation rate and malignant behavior of the cells (17–23).”
From Potential Therapeutic Effects of Exosomes Packed With a miR-21-Sponge Construct in a Rat Model of Glioblastoma (2019) · cites this paper as [19]
Experimental — accuracy not yet measuredThe source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“Previous studies have proven that PDCD4, HNRNPK and RECK are TSGs among the direct targets of miR-21-5p (13,(27)(28)(29).”
From Functional interaction between miR-505-3p and miR-21 contributes to GBM suppression (2026) · cites this paper as [13]
Experimental — accuracy not yet measuredThe cited source says what the claim attributes to it.
In the citing paper
“In particular, miRNA-21 (miR-21) has been shown to be a strong antiapoptotic factor [5, 9–11].”
From MicroRNA‐21 protects neurons from ischemic death (2010) · cites this paper as [11]
The cited source says what the claim attributes to it.
In the citing paper
“We explored miR-21 as a potential biomarker due to its reported association with GBM aggressiveness in previous studies by various research groups [8,23,24].”
From miR-21 as a diagnostic and prognostic biomarker in glioma: tissue and serum expression analysis in a Pakistani cohort (2026) · cites this paper as [23]
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Each contradiction between two passages listed here was confirmed by an independent check.
Rated minor: it would not touch a result — a value no result rests on, a p-value that stays on the same side of the significance level, or a conflict that is clerical, resolved elsewhere in the paper, or outside its own findings.
In the paper
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Dual luciferase assay.
“At 24 h later, three different concentrations 0/12.5/25/50Amol/L of doxorubicin were added to the cells.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
“48 h after transduction, cells were treated with indicated doses of doxorubicin, and apoptosis was assayed 24 h later by caspase-3/7 activity using the Caspase-3/7 Glo.”
Rated minor: it would not touch a result — a value no result rests on, a p-value that stays on the same side of the significance level, or a conflict that is clerical, resolved elsewhere in the paper, or outside its own findings.
In the paper
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > MiR-21 knockdown led to cell cycle arrest.
“At 24 h posttransfection of each siRNA with LNA-scr or LNA-miR-21, we added nocodazole to synchronize cells.At 16 to 20 h later, we harvested the cells and performed PI staining for cell cycle analysis.”
§ MicroRNA-21 Targets a Network of Key Tumor-Suppressive Pathways in Glioblastoma Cells > Discussion
“C, PI staining performed 24 h posttransfection of siRNA sequences for HNRPK, TAp63, and negative control scramble in the presence of LNA-scr or LNA-miR-21.”
Cited works that were retracted
Works this paper cites that were later retracted, from the retraction notices publishers deposit. Major when the notice came out before this paper was published.
A note, not an issue: for example, a cited work that was retracted only after this paper was published, which its authors could not have known.
In the paper
“Moumen A, Masterson P, O'Connor MJ, Jackson SP. hnRNP K: an HDM2 target and transcriptional coactivator of p53 in response to DNA damage. Cell 2005; 123: 1065–78.”
Cited work 10.1016/j.cell.2005.09.032 · retracted 2024-10-31 · notice 10.1016/j.cell.2024.10.008 · this paper published 2008-09-30
Citations
Cites
1 retracted
RETRACTED: hnRNP K: An HDM2 Target and Transcriptional Coactivator of p53 in Response to DNA Damage
Moumen, A., Masterson, P., O'Connor, M. J., & Jackson, S. P. (2005) · Cell · doi:10.1016/j.cell.2005.09.032 · Cited by 350
RetractedHanahan, D., & Weinberg, R. A. (2000) · Cell · doi:10.1016/s0092-8674(00)81683-9 · Cited by 29,219
MicroRNA expression profiles classify human cancers
Lü, J., Getz, G. A., Miska, E. A., Alvarez-Saavedra, E., Lamb, J., Peck, D., Sweet-Cordero, A., Ebert, B. L., Mak, R. H., Ferrando, A. A., et al. (2005) · Nature · doi:10.1038/nature03702 · Cited by 9,637
MicroRNA signatures in human cancers
Calin, G. A., & Croce, C. M. (2006) · Nature reviews. Cancer · doi:10.1038/nrc1997 · Cited by 7,668
Oncomirs—MicroRNAs with a role in cancer
Esquela-Kerscher, A., & Slack, F. J. (2006) · Nature Reviews Cancer · doi:10.1038/nrc1840 · Cited by 5,884
A microRNA expression signature of human solid tumors defines cancer gene targets
Volinia, S., Calin, G. A., Liu, C.-G., Ambs, S., Cimmino, A., Petrocca, F., Visone, R., Iorio, M., Roldo, C., Ferracin, M., et al. (2006) · Proceedings of the National Academy of Sciences · doi:10.1073/pnas.0510565103 · Cited by 5,697
Li, J., Yen, C., Liaw, D., Podsypanina, K., Bose, S., Wang, S. I., Puc, J., Miliaresis, C., Rodgers, L., McCombie, R., et al. (1997) · Science · doi:10.1126/science.275.5308.1943 · Cited by 4,785
Microarray analysis shows that some microRNAs downregulate large numbers of target mRNAs
Lim, L. P., Lau, N. C., Garrett-Engele, P., Grimson, A., Schelter, J. M., Castle, J., Bartel, D. P., Linsley, P. S., & Johnson, J. M. (2005) · Nature · doi:10.1038/nature03315 · Cited by 4,755
MicroRNA Gene Expression Deregulation in Human Breast Cancer
Iorio, M. V., Ferracin, M., Liu, C.-G., Veronese, A., Spizzo, R., Sabbioni, S., Magri, E., Pedriali, M., Fabbri, M., Campiglio, M., et al. (2005) · Cancer Research · doi:10.1158/0008-5472.can-05-1783 · Cited by 4,053
The E6 oncoprotein encoded by human papillomavirus types 16 and 18 promotes the degradation of p53
Scheffner, M., Werness, B. A., Huibregtse, J. M., Levine, A. J., & Howley, P. M. (1990) · Cell · doi:10.1016/0092-8674(90)90409-8 · Cited by 3,995
Cited by
Sorted by citations
Items 701–706 of 706
Xing, Z., Zhao, Q., He, X., Cai, J., Xue, Y., Fenton, C. G., Kantarcı, A., Fenton, K. A., An, X., & Xue, Y. (2026) · Biomedicines · doi:10.3390/biomedicines14051124
Structural remodeling of tumor microtubes in IDH1 mutation shapes microRNA transfer in glioma
Leclerc, A., Levallet, J., Bénard, M., et al. (2026) · Neurobiology of Disease · doi:10.1016/j.nbd.2026.107505
Delshad, S., Jafarinejad-Farsangi, S., Ghasem-Shirazi, M., Kheirandish, R., & Bashiri, H. (2026) · Naunyn-Schmiedeberg's Archives of Pharmacology · doi:10.1007/s00210-026-05705-y
Li, K., Hu, M., Miao, Z., Liu, J., Zhou, C., Lin, W., Xiong, W., Zhang, H., & Zhang, Y. (2026) · Cancer Bioscience · doi:10.1016/j.cbs.2026.100012
Molecular Identification of the Indolent Versus Lethal Tumor
Leyten, G. H. J. M., & Schalken, J. A. (2012) · Humana Press eBooks · doi:10.1007/978-1-62703-182-0_6
Metadata
- Authors
- Papagiannakopoulos, T., Shapiro, A., & Kosik, K. S.
- Affiliations
- University of California, Santa Barbara (US)
- 1Neuroscience Research Institute and
- Venue
- Cancer Research
- Published
- 2008-09-30
- Volume
- 68
- Issue
- 19
- Pages
- 8164-8172
- ISSN
- 0008-5472 (ISSN-L)
- 1538-7445
- OpenAlex
- W2111990378
- Semantic Scholar
- 85ace315e035f7501d4a149af358dd774fa2d616
- Cited by
- 705
- References
- 45
- Citations by year
- 2026: 13 · 2025: 13 · 2024: 18 · 2023: 14 · 2022: 24 · 2021: 29 · 2020: 31 · 2019: 32 · 2018: 36 · 2017: 30 · 2016: 53 · 2015: 55 · 2014: 52 · 2013: 72 · 2012: 79
- FWCI
- 15.56
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Cancer Research (publishedVersion)
- PubMed (publishedVersion)
- Funders
- W. M. Keck Foundation
- Topics
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Cancer Research › MicroRNA in disease regulation
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Cancer Research › Cancer-related molecular mechanisms research
- Health Sciences › Medicine › Oncology › Cancer-related Molecular Pathways
- Keywords
- miR-21, glioblastoma, miRNA target genes, p53 pathway, TGF-beta signaling, mitochondrial apoptosis, tumor suppressor pathways, TAp63, cell proliferation, apoptosis, cell cycle arrest, oncogenes
- MeSH terms
- Cell Cycle, Glioblastoma, HeLa Cells, Humans, Models, Biological, Tumor Cells, Cultured, Signal Transduction, Genes, Tumor Suppressor, Genes, p53, Transforming Growth Factor beta, Apoptosis, Gene Targeting, RNA, Small Interfering, MicroRNAs, Cell Proliferation, Genes, Mitochondrial, Gene Regulatory Networks
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.
A language model drew the claims from the paper on 2026-10-22, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).
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Cited sources are checked with a language model’s help (gpt-6-sol).
Statistics and arithmetic are recomputed, not judged.
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