MicroRNA 21 Promotes Glioma Invasion by Targeting Matrix Metalloproteinase Regulators

In the paper

“Accumulated data suggested that MMP levels and activities are significantly elevated in human gliomas, which contributes to glioma cell invasion of the surrounding normal tissues, metastasis, and angiogenesis through cell surface ECM degradation (21, 45).”

What the sources say

• ?Not checked — no full text of the sourcecites [21] Hu B., 2003, Proc. Natl. Acad. Sci. USA source
• Partly supported

  The Abstract and §4.1 link elevated MMP levels in human gliomas to invasiveness, and describe ECM degradation and cell-surface activation. But the Abstract discusses metastasis in cancer generally, not specifically gliomas; §4.2 links MMP-9 to angiogenesis only tentatively and says its activity in invasive glioma tissue is unproven. The copy therefore does not establish significantly elevated MMP activities across human gliomas or the claimed glioma metastasis and angiogenesis mechanism. Page numbers were not supplied. (LLM, conf=0.88)

  cites [45] sourceExperimental — accuracy not yet measured

In the paper

“TIMP3 is a tissue inhibitor of MMPs that inhibits angiogenesis and tumor cell infiltration and also induces apoptosis (2, 48).”

What the sources say

• Partly supported

  The paper’s Summary (p. 1347) identifies TIMP-3 as a tissue inhibitor of metalloproteinases, and its discussion reports inhibited invasion of HeLa and HT1080 cancer cells and apoptotic death in three cancer cell lines. The copy does not report that TIMP-3 inhibits angiogenesis; searches for angiogenesis and blood-vessel formation found no supporting passage. (LLM, conf=0.88)

  cites [2] sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [48] source

In the paper

“This microRNA has been implicated in various aspects of carcinogenesis, including cellular proliferation, apoptosis, and migration.”

• Also stated in: § Abstract · plain

  “miR-21 has been identified in controlling apoptosis, cell proliferation, and migration of cell lines in breast, colorectal, and other cancers (1, 44, 51, 59).”

What the sources say

• ?Not checked — no full text of the sourcecites [1] source
• Supported

  The Results report that changing miR-21 expression affects proliferation and migration in HCC cells. The Discussion also reports anti-apoptotic properties of miR-21 in glioblastoma and cholangiocarcinoma, supporting the broader statement that it has been implicated in all three processes. (LLM, conf=0.92)

  cites [44] source
• ?Not checked — no full text of the sourcecites [51] source

In the paper

“Our analysis also confirmed tropomyosin 1 (TPM1) regulation by miR-21, previously reported to occur in MCF7 cells (59, 60).”

What the sources say

• Supported

  The Abstract reports that experiments using tumors derived from MCF-7 cells identified TPM1 as a miR-21 target and confirmed that miR-21 down-regulates its expression. The Results section also reports increased endogenous TPM1 in anti-miR-21-treated, MCF-7-derived tumors. The paper therefore supports the cited prior report, although its tumor measurements were made in MCF-7-derived tumors rather than isolated cells. (LLM, conf=0.90)

  cites [59] source
• ?Not checked — no full text of the sourcecites [60] source

In the paper

“Another factor that can induce miR-21 expression is hypoxia, a general feature of all solid tumors (30).”

What the sources say

• Supported

  The Results report miR-21 among the hypoxia-regulated microRNAs and say its microarray result was checked by quantitative RT-PCR. The introductory passage describes hypoxia as an essential feature of the neoplastic microenvironment. (LLM, conf=0.90)

  cites [30] source

In the paper

“The miR-21 gene contains two conserved STAT3 binding sites within its enhancer region and is induced by interleukin 6 (IL-6) in a STAT3-dependent way.”

What the sources say

• Supported

  The Results and discussion section identifies two conserved Stat3 binding sites in the miR-21 upstream regulatory region. It also reports that IL-6 increased miR-21 expression and that Stat3 knockdown inhibited this induction. (LLM, conf=0.94)

  cites [39] source

In the paper

“MMPs can degrade ECM components and therefore play important roles in mediating GBM tumor cell motility and invasion (45).”

What the sources say

• Supported

  The Introduction says MMPs can degrade nearly all ECM macromolecules in the brain and are believed to play a major role in tumor invasion. The Abstract links MMP-mediated ECM degradation to glioblastoma invasion, while Section 4 describes how ECM degradation may permit glioma-cell migration. (LLM, conf=0.92)

  cites [45] source

In the paper

“APAF1 (apoptotic protease activating factor 1) is the molecular core of apoptosome. It is typically required for activation of the caspases that initiate apoptosis (3, 26).”

What the sources say

• Supported

  The Introduction describes Apaf-1 oligomerization as forming the apoptosome, while the Results and discussion state that Apaf-1 normally recruits and activates caspases-9 and -3. The Concluding remarks add that caspase-9 activity depends on interaction with oligomerized Apaf-1. Page numbers are not provided in our copy. (LLM, conf=0.90)

  cites [3] source
• Supported

  The paper’s introductory discussion (page not specified in our copy) says cytochrome c binds Apaf-1, leading to recruitment of procaspase-9 and formation of the apoptosome; the apoptosome then activates caspase-9. In the section on Apaf-1 expression levels (page not specified), adding Apaf-1 enabled cytochrome c to activate caspases in neural extracts, supporting its required role in the pathway described. (LLM, conf=0.91)

  cites [26] Johnson C. E., 2007, Proc. Natl. Acad. Sci. USA source

In the paper

“Elevated miR-21 expression has been causally linked to proliferation, apoptosis, and migration of several cancer cell lines (1, 5, 44, 60).”

What the sources say

• ?Not checked — no full text of the sourcecites [1] source
• ?Not checked — no full text of the sourcecites [5] source
• Supported

  The Results report that experimentally increasing or inhibiting miR-21 changed proliferation and migration in HCC cell lines. The Discussion reports anti-apoptotic properties of miR-21 in glioblastoma and cholangiocarcinoma, supporting the apoptosis part as a finding the paper reports from other studies. (LLM, conf=0.87)

  cites [44] source

In the paper

“miR-21 levels remain low in grade II gliomas and in most grade III tumors and are significantly higher in GBMs (Fig. 1).”

In the paper

“This expression pattern is different from those of the other cancer-associated miRNAs, for example, miR-10b, which is often elevated in grade III and even grade II gliomas (Fig. 1) and dysregulated in some other cancers (41).”

What the sources say

• ?Not checked — no full text of the sourcecites [41] source

In the paper

“RECK mRNA level increased consistently ∼2-fold and TIMP3 mRNA about 1.6-fold in the cells transfected with anti-miR-21.”

In the paper

“These experiments demonstrated that inhibition of miR-21 reduced the motility of glioma cells (Fig. 6B and C).”

In the paper

“We note that, though 2′-O-MOE miR-21 ASO induced many proapoptotic and cell cycle arrest genes (Fig. 2C; also see Table S1 in the supplemental material), it did not significantly and consistently change the viability of glioma cell lines, which was reported for other, less potent miR-21 inhibitors (5, 8).”

What the sources say

• ?Not checked — no full text of the sourcecites [5] source
• ?Not checked — no full text of the sourcecites [8] source

In the paper

“STAT3, the other gene that may play a tumor suppressor function in GBM (11), is also negatively regulated by miR-21 according to the microarray data (see Table S1 in the supplemental material) and is a predicted miR-21 target (29, 34).”

What the sources say

• ?Not checked — no full text of the sourcecites [29] source
• ?Not checked — no full text of the sourcecites [34] source

In the paper

“As identified in our study, TIMP3 or both TIMP3 and RECK are also induced by anti-miR-21 in MCF7 (breast carcinoma) and U2OS (osteosarcoma) cells (Fig. 4D).”

In the paper

“In glioma progression from less invasive grade II gliomas to very invasive GBMs, RECK and TIMP3 levels drop (Fig. 4B), whereas miR-21 expression increases (Fig. 1).”

In the paper

“Here, we show that a 2′-O-MOE ASO not only is potent but also upregulates miR-21 seed-containing mRNAs (Fig. 2 and 3).”

In the paper

“Substantial data indicate that microRNA 21 (miR-21) is significantly elevated in glioblastoma (GBM) and in many other tumors of various origins.”

• Also stated in: § Abstract · boosted

  “Using high-throughput profiling of miRNA expression, we have previously identified a specific miRNA, miRNA 21 (miR-21), as most strongly elevated in nearly all analyzed human GBM specimens (5).”

• Also stated in: § Abstract · boosted

  “Other groups demonstrated overexpression of this miRNA in a wide range of other cancers, including breast, lung, colon, prostate, pancreas, ovarian, and stomach cancers, as well as in chronic lymphocytic leukemia (33, 54).”

What the sources say

• ?Not checked — no full text of the sourcecites [5] source
• ?Not checked — no full text of the sourcecites [33] source
• ?Not checked — no full text of the sourcecites [54] source

In the paper

“mRNAs carrying RECK and TIMP3 are predicted conserved miR-21 targets with one and two putative binding sites, respectively (Fig. 4A).”

In the paper

“The sequences of the control and mismatch oligonucleotides have been analyzed using BLAST searches to exclude potential hits in the human transcriptome.”

In the paper

“RECK is a membrane-anchored MMP inhibitor whose reduced expression or inactivation seems to be critical for the invasiveness and metastasis of various cancers, including glioma cancer (7, 46).”

What the sources say

• ?Not checked — no full text of the sourcecites [7] Correa T. C., 2006, J. Cell. Biochem. source
• ?Not checked — no full text of the sourcecites [46] source

In the paper

“The high level of miR-21 expression in GBMs compared to that in anaplastic astrocytomas suggests the involvement of miR-21 in one of these key processes.”

In the paper

“Its expression level is also an important prognostic factor for multiple cancer types (6).”

What the sources say

• ?Not checked — no full text of the sourcecites [6] source

In the paper

“It has been demonstrated to inhibit MMP activity and tumor growth in malignant gliomas in vivo (31, 32).”

What the sources say

• ?Not checked — no full text of the sourcecites [31] Lam P., 2005, Mol. Ther. source
• ?Not checked — no full text of the sourcecites [32] source

In the paper

“Since modified oligonucleotides can induce a wide range of nonspecific, off-target-mediated effects, several ASO molecules of different chemistries have been used for miR-21 inhibition.”

In the paper

“Our data suggest that miR-21 contributes to glioma malignancy by downregulation of MMP inhibitors, which leads to activation of MMPs, thus promoting invasiveness of cancer cells.”

In the paper

“Such overrepresentation of the hexamers suggests an abundance of direct miR-21 targets among the genes upregulated by 2′-O-MOE anti-miR-21 and indicates that the effects of this molecule on glioma cells are indeed mediated through the miR-21 pathway.”

In the paper

“These experiments have been performed with the miR-21 inhibitor and with a mismatched control oligonucleotide to ensure that any observed effects are driven by miR-21.”

In the paper

“Importantly, it inhibits tumor necrosis factor alpha-converting enzyme and induces apoptosis through the stabilization of tumor necrosis factor alpha receptors on the cell surface (42).”

What the sources say

• ?Not checked — no full text of the sourcecites [42] source

In the paper

“Moreover, it leads to reduction of glioma cell motility and invasion, which is mediated by elevated RECK expression and was partly rescued by RECK siRNA (Fig. 6 and 7).”

In the paper

“This implies that miR-21 regulates RECK and TIMP3 expression and thus MMP activities and glioma tumor invasiveness.”

In the paper

“In this study, we have demonstrated in vitro and in vivo, using U87 glioma xenografts in nude mice, that miR-21 regulates MMPs and glioma cell invasiveness by directly controlling the MMP inhibitor RECK.”

In the paper

“These combined results indicate that miR-21 regulates overlapping though not identical sets of genes in different cells and therefore shares common signaling pathways in different cancers.”

In the paper

“The APAF1 3′ UTR contains a strong miR-21 binding site (9-mer binding at miR-21 5′ end), and therefore, it is likely one of the direct miR-21 targets.”

In the paper

“Its expression is highly upregulated in a variety of solid tumors, including GBM, breast, lung, colon, prostate, pancreas, and stomach cancers (5, 54).”

What the sources say

• ?Not checked — no full text of the sourcecites [5] source
• ?Not checked — no full text of the sourcecites [54] source

In the paper

“Our mRNA expression analysis suggests that miR-21 regulates the expression of multiple mRNA targets and thereby induces several cellular programs in glioma cells, including those associated with the tumor invasiveness and microvascular proliferation typical for the GBM as well as those involved in cell cycle regulation and apoptosis.”

In the paper

“Its ectopic expression in glioma cells induces upregulation of genes associated with angiogenesis, growth factors, cytokines, death receptors, and substrates of the various MMPs (31).”

What the sources say

• ?Not checked — no full text of the sourcecites [31] Lam P., 2005, Mol. Ther. source

In the paper

“RECK, a membrane-anchored regulator, and TIMP3, the ECM-bound protease regulator, are key inhibitors of several MMPs, and their expression is prognostic in a number of common cancers (28, 53).”

What the sources say

• ?Not checked — no full text of the sourcecites [28] Kotzsch M., 2005, Eur. J. Cancer. source
• ?Not checked — no full text of the sourcecites [53] Takenaka K., 2004, Eur. J. Cancer source

In the paper

“TIMP3 has been demonstrated to activate caspases and therefore induce apoptosis of human glioma cells in vitro and the growth inhibition of human glioma tumors in a mouse model (31, 32).”

What the sources say

• ?Not checked — no full text of the sourcecites [31] Lam P., 2005, Mol. Ther. source
• ?Not checked — no full text of the sourcecites [32] source

In the paper

“Though mRNA expression analysis does not allow identification of targets whose translation is regulated without modulation of mRNA levels”

In the paper

“Such a bidirectional approach to manipulating miR-21 levels enabled narrowing of the lists of regulated genes and identification of those whose expression correlated negatively with miR-21 levels”

In the paper

“In these experiments, we used tumorigenic U87 cells, a common model of human gliomas (23).”

What the sources say

• ?Not checked — no full text of the sourcecites [23] source