MicroRNA-566 activates EGFR signaling and its inhibition sensitizes glioblastoma cells to nimotuzumab.

BACKGROUND: Epidermal growth factor receptor (EGFR) is amplified in 40% of human glioblastomas. However, most glioblastoma patients respond poorly to anti-EGFR therapy. MicroRNAs can function as either oncogenes or tumor suppressor genes, and have been shown to play an important role in cancer cell proliferation, invasion and apoptosis. Whether microRNAs can impact the therapeutic effects of EGFR inhibitors in glioblastoma is unknown. METHODS: miR-566 expression levels were detected in glioma cell lines, using real-time quantitative RT-PCR (qRT-PCR). Luciferase reporter assays and Western blots were used to validate VHL as a direct target gene of miR-566. Cell proliferation, invasion, cell cycle distribution and apoptosis were also examined to confirm whether miR-566 inhibition could sensitize anti-EGFR therapy. RESULTS: In this study, we demonstrated that miR-566 is up-regulated in human glioma cell lines and inhibition of miR-566 decreased the activity of the EGFR pathway. Lentiviral mediated inhibition of miR-566 in glioblastoma cell lines significantly inhibited cell proliferation and invasion and led to cell cycle arrest in the G0/G1 phase. In addition, we identified von Hippel-Lindau (VHL) as a novel functional target of miR-566. VHL regulates the formation of the ß-catenin/hypoxia-inducible factors-1α complex under miR-566 regulation. CONCLUSIONS: miR-566 activated EGFR signaling and its inhibition sensitized glioblastoma cells to anti-EGFR therapy.

Rivaroxaban triggered multifocal intratumoral hemorrhage of the cabozantinib-treated diffuse brain metastases: A case report and review of literature.

Brain metastases (BMs) are the most common intracranial malignancy with poor prognosis. Patients with intracranial tumors are at greater risk for thrombotic complications and intracranial hemorrhage. Rivaroxaban is a potent oral anticoagulant with the high selectivity of direct factor Xa inhibition. The incidence and severity of rivaroxaban-triggered intratumoral hemorrhage (ITH) in patients with BMs remain unknown. A 57-year-old woman was diagnosed with multiple lung, bone, and BMs from unknown primary cancer origin, and refused any invasive procedures to confirm tumor pathology. However, this patient had a relatively favorable outcome after treating with cabozantinib, an inhibitor of multiple tyrosine kinases. The patient survived over 2 years and developed deep vein thrombosis of right lower limb. Oral rivaroxaban was prescribed, and the multifocal catastrophic ITH was encountered after 1 week. The last head computed tomography imaging revealed a rare but typical image of diffuse hemorrhagic metastases. Hemorrhagic-prone BMs, therapeutic rivaroxaban, and cabozantinib treatment increase risks to develop ITH. In this case rivaroxaban was the trigger to this terminal event. This case is a miserable lesson and keeps reminding us to stay vigilant in clinical practice even when there is a potential benefit for anticoagulation in such population.

Identification of an epithelial-mesenchymal transition related long non-coding RNA (LncRNA) signature in Glioma.

Epithelial-mesenchymal transition (EMT)-related long non-coding RNAs (lncRNAs) may be exploited as potential therapeutic targets in gliomas. However, the prognostic value of EMT-related lncRNAs in gliomas is unclear. We obtained lncRNAs from The Cancer Genome Atlas and constructed EMT-related lncRNA co-expression networks to identify EMT-related lncRNAs. The Chinese Glioma Genome Atlas (CGGA) was used for validation. Gene set enrichment and principal component analyses were used for functional annotation. The EMT-lncRNA co-expression networks were constructed. A real-time quantitative polymerase chain reaction assay was performed to validate the bioinformatics results. A nine-EMT-related lncRNAs (HAR1A, LINC00641, LINC00900, MIR210HG, MIR22HG, PVT1, SLC25A21-AS1, SNAI3-AS1, and SNHG18) signature was identified in patients with glioma. Patients in the low-risk group had a longer overall survival (OS) than those in the high-risk group (P < 0.0001). Additionally, patients in the high-risk group showed no deletion of chromosomal arms 1p and/or 19q, isocitrate dehydrogenase wild type, and higher World Health Organization grade. Moreover, the signature was identified as an independent factor and was significantly associated with OS (P = 0.041, hazard ratio = 1.806). These findings were further validated using the CGGA dataset. The low- and high-risk groups showed different EMT statuses based on principal component analysis. To study the regulatory function of lncRNAs, a lncRNA-mediated ceRNA network was constructed, which showed that complex interactions of lncRNA-miRNA-mRNA may be a potential cause of EMT progression in gliomas. This study showed that the nine-EMT-related lncRNA signature has a prognostic value in gliomas.

Premature MicroRNA-Based Therapeutic: A "One-Two Punch" against Cancers.

Up-to-date knowledge regarding the biogenesis and functioning of microRNAs (miRNAs) has provided a much more comprehensive and concrete view of miRNA biology than anyone ever expected. Diverse genetic origins and biogenesis pathways leading to functional miRNAs converge on the synthesis of ≈21-nucleotide RNA duplex, almost all of which are processed from long premature sequences in a DICER- and/or DROSHA-dependent manner. Formerly, it was assumed that one mature strand of the duplex is preferentially selected for entry into the silencing complex, and the paired passenger strands (miRNA*) are subjected to degradation. However, given the consolidated evidence of substantial regulatory activity of miRNA* species, currently, this preconception has been overturned. Here, we see the caveat and opportunity toward exogenously manipulating the expression of premature miRNA, leading to simultaneous upregulation or downregulation of dual regulatory strands due to altered expressions. The caveat is the overlooked miRNA* interference while manipulating the expression of a target miRNA at the premature stage, wherein lies the opportunity. If the dual strands of a pre-miRNA function synergistically, the overlooked miRNA* interference may inversely optimize the therapeutic performance. Insightfully, targeting the premature miRNAs may serve as the "one-two punch" against diseases, especially cancers, and this has been discussed in detail in this review.

TGFß signaling-induced miRNA participates in autophagic regulation by targeting PRAS40 in mesenchymal subtype of glioblastoma.

Objective: Mesenchymal subtype of glioblastoma (mesGBM) is a refractory disease condition characterized by therapeutic failure and tumor recurrence. Hyperactive transforming growth factor-ß (TGF-ß) signaling could be a signature event in mesGBM, which leads to dysregulation of downstream targets and contribute to malignant transformation. In this study we aimed to investigate the hyperactive TGFß signaling-mediated pathogenesis and possible downstream targets for the development of novel therapeutic interventions for mesGBM. Methods: GBM-BioDP is an online resource for accessing and displaying interactive views of the TCGA GBM data set. Transcriptomic sequencing followed by bioinformatic analysis was performed to identify dysregulated microRNAs. Target prediction by MR-microT and dual luciferase reporter assay were utilized to confirm the predicted target of novel_miR56. CCK-8 assays was used to assesse cell viability. The miRNA manipulation was proceeded by cell transfection and lentivirus delivery. A plasmid expressing GFP-LC3 was introduced to visualize the formation of autophagosomes. Orthotopic GBM model was constructed for in vivo study. Results: TGFß1 and TGFß receptor type II (TßRII) were exclusively upregulated in mesGBM (P < 0.01). Dysregulated miRNAs were identified after LY2109761 (a TßRI/II inhibitor) treatment in a mesGBM-derived cell line, and novel_miR56 was selected as a promising candidate for further functional verification. Novel_miR56 was found to potentially bind to PRAS40 via seed region complementarity in the 3' untranslated region, and we also confirmed that PRAS40 is a direct target of novel_miR56 in glioma cells. In vitro, over expression of novel_miR56 in tumor cells significantly promoted proliferation and inhibited autophagy (P < 0.05). The expression levels of P62/SQSTM was significantly increased accompanied by the decrease of BECN1 and LC3B-II/I, which indicated that autophagic activity was reduced after novel_miR56 treatment. In addition, over expression of novel_miR56 also promoted tumor growth and inhibited autophagy in vivo, which is associated with worse prognosis (P < 0.05). Conclusions: In summary, we provide novel insight into TGFß signaling-mediated pathogenesis in mesGBM and TGFß signaling-induced novel_miR56 may be a novel target for mesGBM management.

Genomic landscapes by multiregion sequencing combined with circulation tumor DNA detection contribute to molecular diagnosis in glioblastomas.

Glioblastoma is a highly aggressive brain malignancy with a poor prognosis. Its high intratumor heterogeneity contributes to therapeutic resistance, tumor progression and recurrence. We sequenced 31 loci in 11 patients with glioblastoma (including one patient with samples available from the primary and recurrent tumors) to determine the genetic basis and intratumor heterogeneity of glioblastoma. By analyzing the somatic mutations, known driver genes were identified, including EGFR, PTEN and TP53, and the MUC16 gene exhibited the highest mutation rate in the samples examined. Through an evolutionary analysis of the sequencing results, the EGFR p.L861Q mutation was determined to play a role in the progression from the primary tumor to a relapsing tumor in one patient. We analyzed 1403 genes in blood-derived ctDNA that were previously revealed to play a role in tumorigenesis and the progression of cancer. Somatic mutations identified through ctDNA sequencing that match the results of multipoint exon sequencing in tumor tissues were detected, such as EGFR p.L861Q. These findings provide new insights into the intratumor heterogeneity and evolution of glioblastoma. In addition, ctDNA detection in blood samples represents a convenient method to dynamically identify the genetic changes and new therapeutic targets during the treatment of glioblastoma.

Effect of HUK on the outcome of ruptured intracranial aneurysm.

OBJECTIVE: To evaluate the clinical efficacy of Human Urinary Kallidinogenase (HUK) on the outcome of patients with ruptured intracranial aneurysm. METHODS: This was a prospective, open-label study. At the Department of Neurosurgery in our hospital, 127 patients were treated and operated due to ruptured intracranial aneurysm in the period 2015-2016. After surgery, all the patients received basic treatment and 70 patients received additional HUK treatment (HUK group) according to their willing. In detail, 0.15 PNA unit of HUK injection plus 100 ml saline in intravenous infusion was performed, with once a day for 14 consecutive days. The modified Rankin Scale (mRS) scores and favorable mRS rates (mRS 0-1) were analyzed 3-month after the treatment. RESULTS: No difference was shown in the basic characteristics between the two groups (p > 0.05). Favorable mRS rate in the HUK group (71.43%) was significantly higher than that in control group (50.88%, p < 0.05). In addition, 3-month death rate was significantly lower in the HUK group. Delayed ischemic stroke rate was similar between the two groups. CONCLUSION: HUK can reduce morbidity and mortality of patients with ruptured intracranial aneurysm after surgery.

Regulation of human glioma cell apoptosis and invasion by miR-152-3p through targeting DNMT1 and regulating NF2 : MiR-152-3p regulate glioma cell apoptosis and invasion.

BACKGROUND: MiRNAs are involved in aberrant DNA methylation through regulation of DNA methyltransferases (DNMTs) in the pathogenesis and progression of glioblastomas (GBM). MiR-152-3p was down-expressed in human malignancies, and served as a tumor suppressor. Neurofibromatosis type 2 (NF2) was significantly decreased in GBM tissues with a high level of methylation. However, the link between miR-152-3p, DNMT1 and methylation of NF2 in GBM is not clearly established. This study was conducted to detect the mechanism between miR-152-3p, DNMT1 and NF2 in GBM. METHODS: The levels of DNMT1 and NF2 expression were studied by qRT-PCR, Western blot, immunofluorescence, and immumohistochemical staining. Methylation in the promoter region of NF2 was detected by methylation-specific PCR and bisulfate genomic sequencing PCR. Cell proliferation was examined by Cell-Counting Kit-8 and 5-ethynyl-2'-deoxyuridine assay, and cell invasion was evaluated by transwell assay. Flow cytomery and Hoechst staining were used to analyze cell apoptosis. A dual luciferase system was used to confirm the relationship between miR-152-3p and DNMT1. RESULTS: Methylation of NF2 and DNMT1 was markedly increased, and miR-152-3p was downregulated in GBM tissues and glioma cells. Both knockdown of DNMT1 and overexpression miR-152-3p showed that demethylation activated the expression of NF2. Furthermore, miR-152-3p directly targeted DNMT1. Both miR-152-3p overexpression and DNMT1 knockdown significantly induced cell apoptosis and inhibited invasive activity. This was also observed after NF2 overexpression. CONCLUSIONS: These results indicated that miR-152-3p can inhibit glioma cell proliferation and invasion activities by decreasing DNMT1. The restoration of miR-152-3p may have therapeutic application in the treatment of GBM.

F25P preproinsulin abrogates the secretion of pro-growth factors from EGFRvIII cells and suppresses tumor growth in an EGFRvIII/wt heterogenic model.

Extensive heterogeneity is a defining hallmark of glioblastoma multiforme (GBM) at the cellular and molecular levels. EGFRvIII, the most common EGFR mutant, is expressed in 24-67% of cases and strongly indicates a poor survival prognosis. By co-expressing EGFRvIII and EGFRwt, we established an EGFRvIII/wt heterogenic model. Using this approach, we confirmed that a mixture of EGFRvIII and EGFRwt at a certain ratio could clearly enhance tumor growth in vitro and in vivo compared with EGFRwt cells, thereby indicating that EGFRvIII cells promote tumor growth. Furthermore, we demonstrated that the EGFRvIII cells could support the growth of EGFRwt cells by secreting growth factors, thus acting as the principal source for maintaining tumor survival. F25P preproinsulin effectively reduced the concentrations of EGF, VEGF, and MMP-9 in the blood of tumor-bearing mice by competitively inhibiting the endoplasmic reticulum signal peptidase and increased the overall survival in orthotopic models. Taken together, our results provided an effective therapy of F25P preproinsulin in the EGFRvIII/wt heterogenic model.

miRNA interventions serve as 'magic bullets' in the reversal of glioblastoma hallmarks.

microRNAs (miRNAs) are no longer deemed small pieces of RNA "trash" in the human transcriptome but are considered to be master regulators of gene expression that are critical in maintaining cellular homeostasis post-transcriptionally. The concept triggers great interest in studying miRNA dysregulations in human diseases, especially in cancers. Glioblastoma (GBM) has long been the leading cause of the high mortality and morbidity of CNS tumors in adults, which is a consequence of the lack of strategies to reverse the hallmark features of GBM (e.g., borderless expansion and diffuse infiltration). In the past decade, dissecting the molecular architecture of GBM has led to a better understanding of the molecular basis of the hallmarks, generating many promising pharmacological protein targets. However, few clinical responses have been highlighted, suggesting the demand for new therapeutic strategies and targets. In this review, we systemically summarize the context-dependently validated miRNAs with one or more functional targets in the development of GBM hallmarks and review the current miRNA-targeting strategies. We note that only a few miRNA-based therapeutics are trialed for clinical significance, and none of them is tailored to GBM, thereby urging us to bring miRNA therapeutics to the front line either alone or in combination.

HOXA13 is a potential GBM diagnostic marker and promotes glioma invasion by activating the Wnt and TGF-ß pathways.

Homeobox (HOX) genes, including HOXA13, are involved in human cancer. We found that HOXA13 expression was associated with glioma grade and prognosis. Bioinformatics analysis revealed that most of the HOXA13-associated genes were enriched in cancer-related signaling pathways and mainly involved in the regulation of transcription. We transfected four glioma cell lines with Lenti-si HOXA13. HOXA13 increased cell proliferation and invasion and inhibited apoptosis. HOXA13 decreased ß-catenin, phospho-smad2, and phospho-smad3 in the nucleus and increased phospho-ß-catenin in the cytoplasm. Furthermore, downregulation of HOXA13 in orthotopic tumors decreased tumor growth. We suggest that HOXA13 promotes glioma progression in part via Wnt- and TGF-ß-induced EMT and is a potential diagnostic biomarker for glioblastoma and an independent prognostic factor in high-grade glioma.

EZH2 is a negative prognostic factor and exhibits pro-oncogenic activity in glioblastoma.

The identification of single or less genes based on mRNA expression as clinical diagnostic markers for glioblastoma (GBM) remains a challenge. Recent data have shown the potential oncogenic role and prognostic significance of EZH2 in several human cancers. However, the clinical signature and further mechanisms of EZH2 function in gliomagenesis are still poorly understood. In this study, we found that increased EZH2 expression was associated with tumor grade. High expression of EZH2 in GBM was determined to be a strong and independent predictor of short overall survival. Further, we screened EZH2 targets and associated genes in GBM. Repression of EZH2 induced cell cycle arrest and inhibited tumor growth in vivo. This event represents a positive feedback loop with ß-catenin/TCF4 and STAT3 signaling. Taken together, EZH2 could be an independent prognostic factor and potential therapeutic target for GBM.

SNORD76, a box C/D snoRNA, acts as a tumor suppressor in glioblastoma.

Glioblastoma (GBM) is associated with disproportionately high morbidity and mortality, reflecting the need to develop new diagnostic and therapeutic targets for this disease. Recently, accumulating evidence has suggested that small nucleolar RNAs (snoRNAs) are gaining prominence and are more actively involved in tumorigenesis than previously thought. However, no report concerning the implication of snoRNAs in glioma has been published to date. In our study, SNORD76 was first found to be inversely associated with Hox Transcript Antisense Intergenic RNA (HOTAIR) knockdown, and surprisingly, forcibly expressed SNORD76 inhibited proliferation and growth of glioma cells. Moreover, downregulation of SNORD76 led to a more malignant phenotype. The pleiotropy of SNORD76 overexpression could be achieved at least partially through inducing cell cycle arrest at S phase by affecting the Rb-associated cell cycle regulation. Enforced SNORD76 expression in orthotopic tumors resulted in decreased tumor growth and the reduction of tumor volume. Additionally, in surgically resected glioma tissues, SNORD76, not its host gene, was associated with the WHO classification and was selectively downregulated in GBM (WHO grade IV). Collectively, our study adds to a growing body of evidence for the participation of snoRNAs in gliomagenesis and is the first to implicate a snoRNA in glioblastoma.

Long non-coding RNA HOTAIR promotes glioblastoma cell cycle progression in an EZH2 dependent manner.

The long non-coding RNA Hox transcript antisense intergenic RNA (HOTAIR) was recently implicated in breast cancer metastasis and is predictive of poor prognosis in colorectal and pancreatic cancers. We recently discovered that HOTAIR is a cell cycle-related lncRNA in human glioma, and its expression is closely associated with glioma staging and poor prognosis. Although lysine specific demethylase 1 (LSD1) and polycomb repressive complex 2 (PRC2) have been demonstrated to be functional targets of HOTAIR, how HOTAIR regulates glioma cell cycle progression remains largely unknown. In this study, we found that EZH2 (predominant PRC2 complex component) inhibition blocked cell cycle progression in glioma cells, consistent with the effects elicited by HOTAIR siRNA. However, the inhibition of LSD1 did not affect cell cycle progression in glioma cells. These results suggest that HOTAIR might regulate cell cycle progression through EZH2. Our intracranial mice model also revealed delayed tumor growth in HOTAIR siRNA- and EZH2 inhibitor-treated groups. Moreover, in HOTAIR knock-down cell lines, the expression of the PRC2-binding domain of HOTAIR (5' domain) but not of the LSD1-binding domain of HOTAIR (3' domain) resulted in accelerated cell cycle progression. In conclusion, HOTAIR promotes cell cycle progression in glioma as a result of the binding of its 5' domain to the PRC2 complex.

ICAT inhibits glioblastoma cell proliferation by suppressing Wnt/ß-catenin activity.

Inhibitor of ß-catenin and T-cell factor (ICAT) is a key component of Wnt/ß-catenin signaling. ICAT blocks the formation of the ß-catenin/TCF complex and has been demonstrated to be involved in embryonic development and carcinogenesis. As an inhibitor of canonical Wnt signaling, ICAT was presumed to be a tumor-suppressor gene. However, the ICAT functions in human glioma remain unknown. In this study, we evaluated the expression of ICAT in 305 human glioma tissues and found that negative ICAT expression correlated with higher grade glioma and poor survival in patients with glioma. Then we transfected glioma cells with ICAT plasmid. Western blotting showed an increased ICAT protein expression level in glioma cells. MTT assay, flow cytometry and cell invasion assay were used to detect cell proliferation, cell cycle distribution, apoptosis and invasion. Our studies confirmed that ICAT inhibits glioma cell proliferation and invasion, and it induces cell apoptosis and cell cycle progression arrest. Besides, ICAT slowed down tumor growth in a glioblastoma xenograft model. Therefore, our study demonstrates that ICAT may serve as a tumor-suppressor in human glioma suggesting a promising direction for targeting therapy in glioma.

HOTAIR is a therapeutic target in glioblastoma.

HOTAIR is a negative prognostic factor and is overexpressed in multiple human cancers including glioblastoma multiform (GBM). Survival analysis of Chinese Glioma Genome Atlas (CGGA) patient data indicated that high HOTAIR expression was associated with poor outcome in GBM patients. NLK (Nemo-like kinase), a negative regulator of the ß-catenin pathway, was negatively correlated with HOTAIR expression. When the ß-catenin pathway was inhibited, GBM cells became susceptible to cell cycle arrest and inhibition of invasion. Introduction of the HOTAIR 5' domain in human glioma-derived astrocytoma induced ß-catenin. An intracranial animal model was used to confirm that HOTAIR depletion inhibited GBM cell migration/invasion. In the orthotopic model, HOTAIR was required for GBM formation in vivo. In summary, HOTAIR is a potential therapeutic target in GBM.

A lentivirus-mediated miR-23b sponge diminishes the malignant phenotype of glioma cells in vitro and in vivo.

microRNA (miRNA) sponges are RNA molecules with repeated miRNA binding sequences that can sequester miRNAs from their endogenous target mRNAs, and a stably expressed miRNA sponge is particularly valuable for long-term loss-of-function studies in vitro and in vivo. Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults and is characterized by extraordinarily angiogenic, invasive and migratory capabilities, hallmark features that make the disease incurable. Nonetheless, improvements in clinical treatment and a better understanding of the underlying molecular mechanisms have been achieved within the past few decades. miR-23b has previously been found to function as a tumor oncogene in GBM. In the present study, we employed an microRNA sponge that was forcibly expressed using a lentiviral vector to knock down the expression of miR-23b in vitro and in vivo and assessed the pleiotropic effects on glioma angiogenesis, invasion and migration. We demonstrated that the inhibition of miR-23b in glioma cell lines and orthotopic tumor mouse models resulted in a reduction in tumor malignancy, through the downregulation of HIF-1α, ß-catenin, MMP2, MMP9, VEGF and ZEB1 and increased expression of VHL and E-cadherin. Therefore, we suggest that this miR-23b sponge could be developed into a promising anticancer therapy either alone or in combination with current targeted therapies.

BASI, a potent small molecular inhibitor, inhibits glioblastoma progression by targeting microRNA-mediated ß-catenin signaling.

BACKGROUND AND AIMS: The nuclear localization of ß-catenin, a mediator of canonical Wnt signaling, has been indicated in a variety of cancers and is frequently related to tumor progression and metastasis. Therefore, targeting ß-catenin is an attractive therapeutic strategy for cancers. METHODS: Herein, we identified a natural, small molecule inhibitor of ß-catenin signaling, BASI, and evaluated its therapeutic efficacy both in vitro and in orthotopic mouse models of glioma. RESULTS: BASI significantly suppressed proliferation and invasion and induced apoptosis in glioblastoma cells and resulted in the remarkable attenuation of orthotopic tumor growth in vivo. Furthermore, we found that BASI altered the expression of several microRNAs, which mediated the posttranscriptional silencing of ß-catenin expression either directly or indirectly through a von Hippel-Lindau (VHL)-mediated ß-catenin degradation pattern. CONCLUSIONS: Taken together, our findings offer preclinical validation of BASI as a promising new type of ß-catenin inhibitor with a mechanism of inhibition that has broad potential for the improved treatment of glioblastoma.

Blockage of a miR-21/EGFR regulatory feedback loop augments anti-EGFR therapy in glioblastomas.

Epidermal growth factor receptors (EGFR) expression is frequently amplified in human glioblastoma cells. Nimotuzumab, a monoclonal antibody (mAb) against EGFR, has been used globally in clinics as an anti-cancer agent. It is largely unknown whether the blockade of miR-21, a microRNA that is upregulated in glioma cells, could amplify the effects of nimotuzumab. Herein, we have demonstrated that miR-21 directly targets von Hippel-Lindau (VHL) and peroxisome-proliferator-activated receptor α (PPARα) and that miR-21 regulates EGFR/AKT signaling through VHL/ß-catenin and the PPARα/AP-1 axis. Further, the expression of miR-21 is regulated by EGFR via the activation of ß-catenin and AP-1. These data indicate that a feedback loop exists between miR-21 and EGFR. We also show that the combination of nimotuzumab and an inhibitor of miR-21 is superior to single-agent therapy. These results clarify a novel association between miR-21 and EGFR in the regulation of cancer cell progression.

AC1MMYR2, an inhibitor of dicer-mediated biogenesis of Oncomir miR-21, reverses epithelial-mesenchymal transition and suppresses tumor growth and progression.

The extensive involvement of miRNAs in cancer pathobiology has opened avenues for drug development based on oncomir inhibition. Dicer is the core enzyme in miRNA processing that cleaves the terminal loop of precursor microRNAs (pre-miRNAs) to generate mature miRNA duplexes. Using the three-dimensional structure of the Dicer binding site on the pre-miR-21 oncomir, we conducted an in silico high-throughput screen for small molecules that block miR-21 maturation. By this method, we identified a specific small-molecule inhibitor of miR-21, termed AC1MMYR2, which blocked the ability of Dicer to process pre-miR-21 to mature miR-21. AC1MMYR2 upregulated expression of PTEN, PDCD4, and RECK and reversed epithelial-mesenchymal transition via the induction of E-cadherin expression and the downregulation of mesenchymal markers, thereby suppressing proliferation, survival, and invasion in glioblastoma, breast cancer, and gastric cancer cells. As a single agent in vivo, AC1MMYR2 repressed tumor growth, invasiveness, and metastasis, increasing overall host survival with no observable tissue cytotoxicity in orthotopic models. Our results offer a novel, high-throughput method to screen for small-molecule inhibitors of miRNA maturation, presenting AC1MMYR2 as a broadly useful candidate antitumor drug.