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Preeclampsia is a major cause of maternal and fetal mortality and morbidity worldwide. The differential expression of several microRNAs (miRNAs) has been found in preeclamptic placentas. However, great conflict exists regarding this aspect, and detailed examinations have largely been lacking of miRNA profiles in different parts of the placenta and in maternal plasma of women with this disorder. In this study, a total of 9 downregulated miRNAs (miR-195, miR-223, miR-218, miR-17, miR-18a, miR-19bl, miR-92al, miR-379, and miR-411) and 7 upregulated miRNAs (miR-210, miR-30a-3p, miR-518b, miR-524, miR-17-3p, miR-151, and miR-193b) were identified in severe preeclampsia (sPE) placentas when compared with normal pregnant controls. In addition, sampling position in the chorionic or basal plate of placenta led to evident variations in differential miRNAs of sPE placentas. In a prospective pregnant cohort, we found that the circulating levels of 3 members of miR-17-92 cluster (ie, miR-18a, miR-19bl, and miR-92al) were significantly lower, whereas that of miR-210 was higher in sPE patients than those in normal controls at gestational weeks 15 to 18 and at term. The results of in situ hybridization revealed the localization of miR-18a, miR-92al, and miR-210 in various subtypes of placental trophoblasts and endothelial cells. In human trophoblast cell line, HTR8/SVneo cells, miR-18a could promote trophoblast cell invasion via targeting and suppressing Smad2 expression. This study provides fundamental evidences for exploring the roles of miRNAs in the pathogenesis of preeclampsia. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) have been identified to play important functions during osteoblast proliferation, differentiation, and apoptosis. The miR-17~92 cluster is highly conserved in all vertebrates. Loss-of-function of the miR-17-92 cluster results in smaller embryos and immediate postnatal death of all animals. Germline hemizygous deletions of MIR17HG are accounted for microcephaly, short stature, and digital abnormalities in a few cases of Feingold syndrome. These reports indicate that miR-17~92 may play important function in skeletal development and mature. To determine the functional roles of miR-17~92 in bone metabolism as well as osteoblast proliferation and differentiation. Murine embryonic stem cells D3 and osteoprogenitor cell line MC3T3-E1 were induced to differentiate into osteoblasts; the expression of miR-17-92 was assayed by quantitative real-time RT-PCR. The skeletal phenotypes were assayed in mice heterozygous for miR- 17~ 92 ( miR- 17~ 92). To determine the possibly direct function of miR-17~92 in bone cells, osteoblasts from miR- 17~ 92 mice were investigated by ex vivo cell culture. miR-17, miR-92a, and miR-20a within miR-17-92 cluster were expressed at high level in bone tissue and osteoblasts. The expression of miR-17-92 was down-regulated along with osteoblast differentiation, the lowest level was found in mature osteoblasts. Compared to wildtype controls, miR- 17- 92 mice showed significantly lower trabecular and cortical bone mineral density, bone volume and trabecular number at 10 weeks old. mRNA expression of Runx2 and type I collagen was significantly lower in bone from miR- 17- 92 mice. Osteoblasts from miR- 17- 92 mice showed lower proliferation rate, ALP activity and less calcification. Our research suggests that the miR-17-92 cluster critically regulates bone metabolism, and this regulation is mostly through its function in osteoblasts. [ABSTRACT FROM AUTHOR]

Chronic myeloid leukemia accounts for human deaths worldwide and could enhance sevenfold by 2050. Thus, the treatment regimen for this disorder is highly crucial at this time. Flavaglines are a natural class of cyclopentane benzofurans exhibiting various bioactivities like anticancer action. Despite the antiproliferative activity of flavaglines against diverse cancer cells, their roles and mechanism of action in chronic myeloid leukemia (CML) remain poorly understood. Thus, this study examines the antiproliferative effect of a newly synthesized flavagline derivative, 1-chloracetylrocaglaol (A2074), on erythroleukemia K562 cells and the zebrafish xenograft model. The study revealed that A2074 could inhibit proliferation, promote apoptosis, and boost megakaryocyte differentiation of K562 cells. This flavagline downregulated c-MYC and miR-17-92 cluster genes, targeting upregulation of the apoptotic protein Bcl-2-like protein 11 (BIM). The work uncovered a critical role of the c-MYC-miR-17-92-BIM axis in the growth and survival of CML cells., (© 2022 Deutsche Pharmazeutische Gesellschaft.)

Human gastric cancers contain a population of gastric cancer stem cells (GCSCs) that can undergo self-renewal and multipotent differentiation. GCSCs can be enriched with EpCAM+/CD44+ gastric cancer cells. However, the underlying mechanisms controlling the balance of GCSC self-renewal and differentiation remain to be explored. Because miRNAs can regulate cancer cell fates, we compared miRNA expression in tumorspheric cancer cells enriched with GCSCs and more differentiated cells. We found that the miR-17-92 cluster members miR-19b, miR-20a and miR-92a were gradually reduced during the differentiation of GCSCs. Therefore, we speculated that miR-17-92 members might regulate the self-renewal ability of GCSCs. By downregulating miR-19b, miR-20a and miR-92a in EpCAM+/CD44+ GCSCs, or overexpressing them in EpCAM2/CD442 non-GCSC populations, we found that miR-19b, miR-20a and miR-92a could sustain the self-renewal function of GCSCs. Furthermore, we found that miR-19b, miR-20a and miR-92a could also promote the proliferation of gastric cancer cells miR-17-92 targeted the E2F1 and HIPK1 proteins, which suppressed Wnt-β-catenin signaling. A real-time PCR analysis of miR-19b, miR-20a and miR-92a expression in 97 gastric cancer specimens suggested that miR- 92a could be used as an independent prognostic factor in gastric cancer. This study showed that several members of the miR-17-92 cluster, miR-19b, miR-20a and miR-92a, might play important roles in the development of gastric cancer stem cells and that miR-92a has the potential to be used as a predictive prognostic marker in gastric cancer. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) regulate post-transcriptional gene expression in various physiological and pathological processes, including viral infections. The miR-17-92 cluster encodes six miRNAs (miR-17-5p, miR-18a, miR-19a, miR-19b, miR-20a, and miR-92a-1) which are transactivated by c-Myc. Because hepatitis B virus transactivates c-Myc, the interaction between the miR-17-92 cluster and HBV replication was examined in this study. Inducing HBV replication in a human hepatoma cell line increased miR-17-5p, miR-20a and miR-92a-1 expression. HBV-induced overexpression of miR-17-92 was reversed by c-Myc knockdown. Antisense peptide nucleic acids against miR-20a and miR-92a-1 augmented HBV replication. A computational analysis yielded potential binding sites for miR-20a and miR-92a-1 in the HBV genome. The direct interaction between these two miRNAs and target regions in HBV transcripts was confirmed by luciferase reporter analysis. These results demonstrated negative feedback suppression of HBV replication by the miR-17-92 polycistron. J. Med. Virol. 85: 969-978, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Micro RNAs (mi RNAs) are emerging as key controllers of T-cell differentiation and function. Their expression is dynamically regulated by extracellular signals such as costimulation and cytokine signals. mi RNAs set thresholds for gene expression and optimize protein concentrations of genetic networks. Absence of individual mi RNAs can lead to severe immune dysfunction. In this study, we review emerging principles and provide examples of important functions exerted by mi RNAs. Although our understanding of mi RNA function in T-cell differentiation is still rudimentary, the available evidence leaves no doubt that these small post-transcriptional regulators are indispensable for proper functioning of the immune system. [ABSTRACT FROM AUTHOR]

miR-17-5p is abnormally expressed in various tumor types. The aim of this study was to investigate the expression level of miR-17-5p in serum of patients with lung cancer and to determine whether serum miR-17-5p expression is related to the prognosis of patients with lung cancer. RT-qPCR was used to examine expression of miRNA-17-5p in 20 pairs of lung cancer and adjacent normal tissues, and sera from 221 patients with lung cancer and 54 matched controls. The correlation of serum miR-17-5p with clinicopathological factors or prognosis of patients with lung cancer was analyzed. The expression level of miR-17-5p obviously increased in lung cancer tissues ( P = 0.004). Furthermore, serum miR-17-5p expression also significantly increased in patients with lung cancer compared with healthy individuals ( P = 0.03). The survival analysis showed that serum miR-17-5p expression was closely related to the survival of patients with lung cancer. Patients with high miR-17-5p expression had shorter survival times [hazard ratio (HR) = 1.767, 95 %CI 1.039-3.005, P = 0.035]. A lower expression level of serum miR-17-5p helps extend the survival of patients with lung cancer. Thus, miR-17-5p may be potential biomarker for prediction the prognosis in patients with lung cancer. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are important players of post-transcriptional gene regulation. Individual miRNAs can target multiple mRNAs and a single mRNA can be targeted by many miRNAs. We hypothesized that miRNAs select and regulate their targets based on their own expression levels, those of their target mRNAs and triggered feedback loops. We studied the effects of varying concentrations of let-7a-7f and the miR-17-92 cluster plasmids on the reporter genes carrying either DICER- or cMYC -3′UTR in Huh-7 cells. We showed that let-7 significantly downregulated expression of DICER 3′UTR reporter at lower concentrations, but selectively downregulated expression of a cMYC 3′UTR reporter at higher dose. This miRNA dose-dependent target selection was also confirmed in other target genes, including CCND1, CDKN1 and E2F1. After overexpressing let-7a-7f or the miR-17-92 clusters at wide-ranging doses, the target genes displayed a nonlinear correlation to the transfected miRNA. Further, by comparing the expression levels of let-7a and miR-17-5p, along with their selected target genes in 3 different cell lines, we found that the knockdown dose of each miRNA was directly related to their baseline expression level, that of the target gene and feedback loops. These findings were supported by gene modulation studies using endogenous levels of miR-29, -1 and -206 and a luciferase reporter system in multiple cell lines. Finally, we determined that the miR-17-92 cluster affected cell viability in a dose-dependent manner. In conclusion, we have shown that miRNAs potentially select their targets in a dose-dependent and nonlinear fashion that affects biological function; and this represents a novel mechanism by which miRNAs orchestrate the finely tuned balance of cell function. [ABSTRACT FROM AUTHOR]

Antisense inhibition of oncogenic or other disease-related miRNAs and miRNA families in vivo may provide novel therapeutic strategies. However, this approach relies on the development of potent miRNA inhibitors and their efficient delivery into cells. Here, we introduce short seed-directed LNA oligonucleotides (12- or 14-mer antiseeds) with a phosphodiester backbone (PO) for efficient miRNA inhibition. We have analyzed such LNA (PO) antiseeds using a let-7a-controlled luciferase reporter assay and identified them as active miRNA inhibitors in vitro. Moreover, LNA (PO) 14-mer antiseeds against ongogenic miR-17–5p and miR-20a derepress endogenous p21 expression more persistently than corresponding miRNA hairpin inhibitors, which are often used to inhibit miRNA function. Further analysis of the antiseed-mediated derepression of p21 in luciferase reporter constructs—containing the 3'-UTR of p21 and harboring two binding sites for miRNAs of the miR-106b family—provided evidence that the LNA antiseeds inhibit miRNA families while hairpin inhibitors act in a miRNA-specific manner. The derepression caused by LNA antiseeds is specific, as demonstrated via seed mutagenesis of the miR-106b target sites. Importantly, we show functional delivery of LNA (PO) 14-mer antiseeds into cells upon complexation with polyethylenimine (PE I F25-LMW), which leads to the formation of polymeric nanoparticles. In contrast, attempts to deliver a functional seed-directed tiny LNA 8-mer with a phosphorothioate backbone (PS) by formulation with PE I F25-LMW remained unsuccessful. In conclusion, LNA (PO) 14-mer antiseeds are attractive miRNA inhibitors, and their PE I-based delivery may represent a promising new strategy for therapeutic applications. [ABSTRACT FROM AUTHOR]

Abstract: MicroRNA (miR) are emerging as important gene expression regulators often involved in a variety of pathogenesis such as cancers and autoimmunity. Signal transducers and activators of transcription (STAT) proteins are the principle signaling proteins for many cytokines and growth factors, thereby play a critical role in regulating immune cell homeostasis, differentiation and cellular functions. In this review, we discuss recent advances in the field demonstrating active interactions between STATs and miRs, with our primary focus on the promotion and inhibition of immune cells and cancer. Additionally, we review the reciprocal regulations between STATs and miR, and discuss how we can use this knowledge in the context of diseases. For example, recent findings related to STAT1 and miR-155 support the presence of a positive feedback loop of miR-155 and STAT1 in response to inflammatory signals or infection. STAT3 is known to play critical roles in tumorigenesis and cancer-induced immunosuppression. There is a growing body of evidence demonstrating that STAT3 directly activates miR-21, one of miRs that promote cancer cell survival and proliferation. While some miRs directly regulate STATs, there are findings demonstrating indirect STAT regulation by miRs also mediate important biological mechanisms. Therefore, further research is warranted to elucidate significant contributions made by direct and indirect miR–STAT mechanisms. As we learn more about miR pathways, we gain the opportunity to manipulate them in cancer cells to slow down growth or increase their susceptibility anti-tumor immunity. [Copyright &y& Elsevier]

Abstract: Osteosarcoma (OS) is the common histological form of primary bone cancer and one of the leading aggressive cancers in children under age fifteen. Although several genetic predisposing conditions have been associated with OS the understanding of its molecular etiology is limited. Here, we show that microRNAs (miRNAs) at the chr.14q32 locus are significantly downregulated in osteosarcoma compared to normal bone tissues. Bioinformatic predictions identified that a subset of 14q32 miRNAs (miR-382, miR-369-3p, miR-544 and miR-134) could potentially target cMYC transcript. The physical interaction between these 14q32 miRNAs and cMYC was validated using reporter assays. Further, restoring expression of these four 14q32 miRNAs decreased cMYC levels and induced apoptosis in Saos2 cells. We also show that exogenous expression of 14q32 miRNAs in Saos2 cells significantly downregulated miR-17–92, a transcriptional target of cMYC. The pro-apoptotic effect of 14q32 miRNAs in Saos2 cells was rescued either by overexpression of cMYC cDNA without the 3′UTR or with miR-17–92 cluster. Further, array comparative genomic hybridization studies showed no DNA copy number changes at 14q32 locus in OS patient samples suggesting that downregulation of 14q32 miRNAs are not due to deletion at this locus. Together, our data support a model where the deregulation of a network involving 14q32 miRNAs, cMYC and miR-17–92 miRNAs could contribute to osteosarcoma pathogenesis. [Copyright &y& Elsevier]

Abstract: MicroRNAs (miRNAs) are an abundant class of small non-coding RNAs (ncRNAs) that function to regulate gene expression at the post-transcriptional level. Although their functions were originally described during normal development, miRNAs have emerged as integral components of the oncogenic and tumor suppressor network, regulating nearly all cellular processes altered during tumor formation. In particular, mir-17-92, a miRNA polycistron also known as oncomir-1, is among the most potent oncogenic miRNAs. Genomic amplification and elevated expression of mir-17-92 were both found in several human B-cell lymphomas, and its enforced expression exhibits strong tumorigenic activity in multiple mouse tumor models. mir-17-92 carries out pleiotropic functions during both normal development and malignant transformation, as it acts to promote proliferation, inhibit differentiation, increase angiogenesis, and sustain cell survival. Unlike most protein coding genes, mir-17-92 is a polycistronic miRNA cluster that contains multiple miRNA components, each of which has a potential to regulate hundreds of target mRNAs. This unique gene structure of mir-17-92 may underlie the molecular basis for its pleiotropic functions in a cell type- and context-dependent manner. Here we review the recent literature on the functional studies of mir-17-92 and highlight its potential impacts on the oncogene network. These findings on mir-17-92 indicate that miRNAs are integrated components of the molecular pathways that regulate tumor development and tumor maintenance. [Copyright &y& Elsevier]

The miR-17–92 cluster encoding 6 single mature miRNAs was identified a couple of years ago to contain the first oncogenic miRNAs. Now, one of these 6 miRNAs, miR-19 has been identified as the key responsible for this oncogenic activity. This in turn reduces PTEN levels and in consequence activates the AKT/mTOR pathway that is also prominently involved in modulation of organismal life spans. In contrast, miR-19 and other members of the miR-17–92 cluster are found to be commonly downregulated in several human replicative and organismal aging models. Taken together, these findings suggest that miR-19 and the other members of the miR-17–92 cluster might be important regulators on the cross-roads between aging and cancer. Therefore, we here briefly summarize how this cluster is transcriptionally regulated, which target mRNAs have been confirmed so far and how this might be linked to modulation of organismal life-spans. [ABSTRACT FROM AUTHOR]

Aurora kinase A (AURKA) is an essential mitotic serine/threonine kinase and its abnormal expression is observed in many malignancies, yet the exact role for AURKA in tumorigenesis still remains elusive. Here, through a transcription factor array, we show that the transcription activity of E2F1 was increased by AURKA overexpression. Meanwhile, the E2F1 protein level was found to be upregulated and a correlation between AURKA and E2F1 expression was observed in cancer specimens. Further analysis revealed that AURKA increased E2F1 protein stability by inhibiting proteasome-dependent degradation of this protein. Additionally, a microRNA cluster, miR-17-92, was found to be upregulated upon AURKA overexpression, and this stimulation was largely repressed by E2F1 knockdown. Chromatin immunoprecipitation further demonstrated that AURKA enhanced E2F1 occupancy to the promoter of the miR- 17- 92 cluster. These data reveal a novel link between AURKA and microRNAs via the regulation of E2F1, providing new clues for understanding the role of AURKA in tumorigenesis. [ABSTRACT FROM AUTHOR]

All-trans retinoic acid is a potent promoter of cellular differentiation processes, which is used in cancer therapy. Glioblastoma spheroid cultures are enriched in tumor-initiating cells, and provide a model to test new treatment options in vitro. We investigated the molecular mechanisms of response to exposure to differentiation-promoting conditions in such cultures. Microarray analyses of five independent cultures showed that after induction of differentiation, inhibitors of transforming growth factor-β/bone morphogenetic protein, Wnt/β-catenin and IGF signaling were upregulated, whereas expression of several microRNAs decreased, particularly that of the miR-17-92 cluster. In primary astrocytic gliomas (n=82), expression of several members of miR-17-92 was significantly higher relative to those of normal brain (n=8) and significantly increased with tumor grade progression (P<0.05). A high-level amplification of the miR-17-92 locus was detected in one glioblastoma specimen. Transfection of inhibitors of miR-17-92 induced increased apoptosis and decreased cell proliferation in glioblastoma spheroids. Mir-17-92 inhibition was also associated with increased messenger RNA (mRNA) and/or protein expression of CDKN1A, E2F1, PTEN and CTGF. The CTGF gene was shown to be a target of miR-17-92 in glioblastoma spheroids by luciferase reporter assays. Our results suggest that miR-17-92 and its target CTGF mediate effects of differentiation-promoting treatment on glioblastoma cells through multiple regulatory pathways. [ABSTRACT FROM AUTHOR]

The discovery of microRNAs (miRNAs) has revealed a new layer of gene expression regulation that affects many normal and pathologic biological systems. Among the malignancies affected by the dysregulation of miRNAs, there are cancers of lymphoid origin in which miRNAs are thought to have tumor suppressive or tumor promoting activities, depending on the nature of their specific targets. In the last four to five years, the experimental field that provided the deepest insights into the in vivo biology of miRNAs is that of mouse modeling, in which transgenic and knockout animals mimic over-expression or down-regulation, respectively, of specific miRNAs involved in human leukemia/lymphoma. This review discusses recent advances in our understanding of lymphoid malignancies based on the natural and engineered mouse models of three different miRNAs: miR-15a/16-1 cluster, miR-155, and miR-17-92 cluster. [ABSTRACT FROM AUTHOR]

Recent studies have revealed the importance of multiple microRNAs (miRNAs) in promoting tumorigenesis, among which mir-17-92/Oncomir-1 exhibits potent oncogenic activity. Genomic amplification and elevated expression of mir-17-92 occur in several human B-cell lymphomas, and enforced mir-17-92 expression in mice cooperates with c-myc to promote the formation of B-cell lymphomas. Unlike classic protein-coding oncogenes, mir-17-92 has an unconventional gene structure, where one primary transcript yields six individual miRNAs. Here, we functionally dissected the individual components of mir-17-92 by assaying their tumorigenic potential in vivo. Using the Eμ1/4-myc model of mouse B-cell lymphoma, we identified miR-19 as the key oncogenic component of mir-17-92, both necessary and sufficient for promoting c-myc-induced lymphomagenesis by repressing apoptosis. The oncogenic activity of miR-19 is at least in part due to its repression of the tumor suppressor Pten. Consistently, miR-19 activates the Akt?"mTOR (mammalian target of rapamycin) pathway, thereby functionally antagonizing Pten to promote cell survival. Our findings reveal the essential role of miR-19 in mediating the oncogenic activity of mir-17-92, and implicate the functional diversity of mir-17-92 components as the molecular basis for its pleiotropic effects during tumorigenesis. [ABSTRACT FROM AUTHOR]

Abstract: Whole-genome microRNA and gene expression analyses were used to monitor changes during retinoic acid induced differentiation of neuroblasts in vitro. Interestingly, the entire miR-17 family was over-represented among the down-regulated miRNA. The implications of these changes are considerable, as target gene prediction suggests that the miR-17 family is involved in the regulation of the mitogen-activated protein kinase (MAPK) signaling pathway, synaptic plasticity and other markers of neuronal differentiation. Significantly, many of the target responses predicted by changes in miRNA expression were supported by the observed changes in gene expression. As expected, markers of neuronal differentiation such as anti-apoptotic protein B-cell lymphoma 2 (BCL2), myocyte enhancer factor-2D (MEF2D) and zipper protein kinase (MAP3K12; aka ZPK/MUK/DLK) were each up-regulated in response to differentiation. The expression of these genes was also reduced in response to miR-17 and miR-20a transfection, and more specifically they were also shown to contain functional miRNA recognition elements for members of the miR-17 family by reporter gene assay. This suggests that the miR-17 family have an integral role in fine-tuning the pathways involved in the regulation of neuronal differentiation. [Copyright &y& Elsevier]

Abstract: MicroRNAs constitute a family of small RNA species that regulate translation and stability of mRNA. This additional layer of epigenetic regulation has escaped discovery until recently, and introduces another level between mRNA expression profiling and proteomics. Since microRNAs are involved in regulating most, if not all cellular processes, their involvement in oncogenesis was anticipated. Indeed, soon after their discovery, microRNAs were found to act as tumor suppressor genes by blocking the translation of oncogenes and act as oncogenes by inhibiting the translation of tumor suppressor genes. Here we review the most recent attempts aiming to analyze the functional roles of microRNAs in neuroblastoma, the most devastating solid tumor in childhood. [Copyright &y& Elsevier]

Abstract: microRNAs are a class of small RNA molecules that associate with Argonaute proteins to regulate gene expression. Argonaute proteins not only mediate the functions of microRNAs, but also play an essential role in the biogenesis of microRNAs. Here, we report that stable, long-term overexpression of Argonaute2, an Argonaute isoform, induces the production of a number of microRNAs, such as the let-7 family of microRNAs, in 293T cells. On the other hand, the expression of many microRNAs is insensitive to elevated Argonaute levels, and microRNAs in the miR-17-92 and homologous clusters are even down-regulated. The down-regulation may result from the let-7-mediated inhibition of the expression of Myc, which positively controls the transcription of the microRNAs clusters. Our data suggest that human cells have a mechanism for microRNA homeostasis, and that overexpression of a general microRNA processing factor can differentially regulate the expression of specific microRNAs. [Copyright &y& Elsevier]

The NK-like family of homeobox genes includes TLX1, TLX3 and NKX2-5, which are ectopically activated in distinct subsets of T-cell acute lymphoblastic leukemia (T-ALL) cells. Here we analysed their effect on the miR-17-92 cluster overexpressed in several types of cancer, including T-ALL. The pri-miR-17-92 polycistron encodes micro-RNAs (miRNAs), which decrease E2F1 protein expression, regulating proliferation and/or apoptosis. Quantification of pri-miR-17-92 in T-ALL cell lines suggested an implication of the NK-like homeodomain proteins in transcriptional regulation. Lentiviral-mediated overexpression of NKX2-5 in the T-ALL cell line MOLT-4 consistently resulted in increased miR-17-92 pri-miRNA levels and decreased amounts of E2F1 protein. Induction of apoptosis by treating miR17-92 or E2F1 transduced T-ALL cells with etoposide led to reduced or enhanced cell viability, respectively. Furthermore, analysis of pri-miR-17-92 in T-ALL patients indicated elevated expression in those bearing TLX1/3 positive cells. These data support an activatory effect of NK-like homeodomain proteins on pri-miR-17-92 expression and concomitantly reduced E2F1 protein levels, thereby enhancing survival of leukemic T-cells. [ABSTRACT FROM AUTHOR]

Abstract: PTPRO is often silenced by DNA hypermethylation in primary human tumors and cancer cell lines and functions as a tumor suppressor. Here we show that PTPRO is a target of E2F1. In addition, the microRNA cluster miR-17-92, another target of E2F1, participates in PTPRO regulation. PTPRO mRNA was up-regulated during S phase in synchronized HeLa cells and in vitro PTPRO promoter activity is high in early S phase while the PTPRO 3′UTR reporter activity is low in late S phase. This study provides evidence that the PTPRO gene is co-regulated by both E2F1 and miR-17-92. [Copyright &y& Elsevier]

Abstract: The miR-17-92 locus encodes a cluster of 7 microRNAs transcribed as a single primary transcript. It can accelerate c-Myc induced B cell lymphoma development and is highly expressed in many tumors, including lung tumors. However, the role of miR-17-92 in development has not been well studied. From analysis of microRNAs during lung development, expression of the miR-17-92 cluster is high at early stages, but declines as development proceeds. We used the mouse surfactant protein C (Sftpc) promoter to over-express the cluster in embryonic lung epithelium. Transgenic lungs have a very abnormal lethal phenotype. They contain numerous proliferative epithelial cells that retain high levels of Sox9, a marker of distal progenitors. The differentiation of proximal epithelial cells was also inhibited. Furthermore, a significant increase in the number of neuroendocrine cell clusters was observed in the lungs of dead transgenic pups. We identify a tumor suppressor, Rbl2 which belongs to the Rb family, as a new target for miR-17-5p. Together, these studies suggest that mir-17-92 normally promotes the high proliferation and undifferentiated phenotype of lung epithelial progenitor cells. [Copyright &y& Elsevier]

MicroRNAs (miRs) are non-coding master regulators of transcriptome that could act as tumor suppressors (TSs) or oncogenes (oncomiRs). We aimed to systematically investigate the relevance of miRs as prognostic biomarkers in primary glioblastoma multiforme (GBM) treated with postoperative radio(chemo)therapy (PORT). For hypothesis generation, tumor miR expression by Agilent 8x15K human microRNA microarrays and survival data from 482 GBM patients of The Cancer Genome Atlas (TCGA cohort) were analyzed using Cox-PH models. Expression of candidate miRs with prognostic relevance (miR-221/222; miR-17-5p, miR-18a, miR-19b) was validated by qRT-PCR using Taqman technology on an independent validation cohort of GBM patients (n = 109) treated at Heidelberg University Hospital (HD cohort). In TCGA, 50 miRs showed significant association with survival. Among the top ranked prognostic miRs were members of the two miR families miR-221/222 and miR-17-92. Loss of miR-221/222 was correlated with improved prognosis in both cohorts (TCGA, HD) and was an independent prognostic marker in a multivariate analysis considering demographic characteristics (age, sex, Karnofsky performance index (KPI)), molecular markers (O-6-methylguanine-DNA methyltransferase (MGMT) methylation, IDH mutation status) and PORT as co-variables. The prognostic value of miR-17-92 family members was ambiguous and in part contradictory by direct comparison of the two cohorts, thus warranting further validation in larger prospective trials. [ABSTRACT FROM AUTHOR]

Numerous molecular factors disrupt the correctness of the cell cycle process leading to the development of cancer due to increased cell proliferation. Among known causative factors of such process is abnormal gene expression. Nowadays in the light of current knowledge such alterations are frequently considered in the context of mRNA–miRNA correlation. One of the molecular factors with potential value in tumorigenesis is the feedback loop between MYC and E2F genes in which miR-17-5p and miR-20a from the miR-17-92 cluster are involved. The current literature shows that overexpression of the members of the OncomiR-1 are involved in the development of many solid tumors. In the present work, we investigated the expression of components of the MYC/E2F/miR-17-92 network and their closely related elements including members of MYC and E2F families and miRNAs from two paralogs of miR-17-92: miR-106b-25 and miR-106a-363, in the most common brain tumors of childhood, pilocytic astrocytoma (PA), WHO grade 1; ependymoma (EP), WHO grade 2; and medulloblastoma (MB), WHO grade 4. We showed that the highest gene expression was observed in the MYC family for MYCN and in the E2F family for E2F2. Positive correlation was observed between the gene expression and tumor grade and type, with the highest expression being noted for medulloblastomas, followed by ependymomas, and the lowest for pilocytic astrocytomas. Most members of miR-17-92, miR-106a-363 and miR-106b-25 clusters were upregulated and the highest expression was noted for miR-18a and miR-18b. The rest of the miRNAs, including miR-19a, miR-92a, miR-106a, miR-93, or miR-25 also showed high values. miR-17-5p, miR-20a obtained a high level of expression in medulloblastomas and ependymomas, while close to the control in the pilocytic astrocytoma samples. miRNA expression also depended on tumor grade and histology. [ABSTRACT FROM AUTHOR]

An important event in the unfolded protein response (UPR) is activation of the endoplasmic reticulum (ER) kinase PERK. The PERK signalling branch initially mediates a prosurvival response, which progresses to a proapoptotic response upon prolonged ER stress. However, the molecular mechanisms of PERK-mediated cell death are not well understood. Here we show that expression of the primary miR-17-92 transcript and mature miRNAs belonging to the miR-17-92 cluster are decreased during UPR. We found that miR-17-92 promoter reporter activity was reduced during UPR in a PERK-dependent manner. Furthermore, we show that activity of the miR-17-92 promoter is repressed by ectopic expression of ATF4 and NRF2. Promoter deletion analysis mapped the region responding to UPR-mediated repression to a site in the proximal region of the miR-17-92 promoter. Hypericin-mediated photo-oxidative ER damage reduced the expression of miRNAs belonging to the miR-17-92 cluster in wild-type but not in PERK-deficient cells. Importantly, ER stress-induced apoptosis was inhibited upon miR-17-92 overexpression in SH-SY5Y and H9c2 cells. Our results reveal a novel function for ATF4 and NRF2, where repression of the miR-17-92 cluster plays an important role in ER stress-mediated apoptosis. Mechanistic details are provided for the potentiation of cell death via sustained PERK signalling mediated repression of the miR-17-92 cluster. [ABSTRACT FROM AUTHOR]

Aims: Deregulation of mTOR (mammalian target of rapamycin) signalling occurs in diabetes, which exacerbates injury following myocardial infarction (MI). We therefore investigated the infarct-limiting effect of chronic treatment with rapamycin (RAPA, mTOR inhibitor) in diabetic mice following myocardial ischaemia/reperfusion (I/R) injury and delineated the potential protective mechanism., Methods and Results: Adult male diabetic (db/db) or wild-type (WT) (C57) mice were treated with RAPA (0.25 mg/kg/day, intraperitoneal) or vehicle (5% DMSO) for 28 days. The hearts from treated mice were subjected to global I/R in Langendorff mode. Cardiomyocytes, isolated from treated mice, were subjected to simulated ischaemia/reoxygenation (SI/RO) to assess necrosis and apoptosis. Myocardial infarct size was increased in diabetic heart following I/R as compared to WT. Likewise, enhanced necrosis and apoptosis were observed in isolated cardiomyocytes of diabetic mice following SI/RO. Treatment with RAPA reduced infarct size as well as cardiomyocyte necrosis and apoptosis of diabetes and WT mice. RAPA increased STAT3 phosphorylation and miRNA-17/20a expression in diabetic hearts. In addition, RAPA restored AKT phosphorylation (target of mTORC2) but suppressed S6 phosphorylation (target of mTORC1) following I/R injury. RAPA-induced cardioprotection against I/R injury as well as the induction of miR-17/20a and AKT phosphorylation were abolished in cardiac-specific STAT3-deficient diabetic mice, without alteration of S6 phosphorylation. The infarct-limiting effect of RAPA was obliterated in cardiac-specific miRNA-17-92-deficient diabetic mice. The post-I/R restoration of phosphorylation of STAT3 and AKT with RAPA were also abolished in miRNA-17-92-deficient diabetic mice. Additionally, RAPA suppressed the pro-apoptotic prolyl hydroxylase (Egln3/PHD3), a target of miRNA-17/20a in diabetic hearts, which was abrogated in miRNA-17-92-deficient diabetic mice., Conclusion: Induction of STAT3-miRNA-17-92 signalling axis plays a critical role in attenuating MI in RAPA-treated diabetic mice. Our study indicates that chronic treatment with RAPA might be a promising pharmacological intervention for attenuating MI and improving prognosis in diabetic patients., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2019. For permissions, please email: journals.permissions@oup.com.)

We established a semi-high-throughput in vivo screening platform using hyperactive piggyBac (hyPB) transposons (designated as PB-miR) to identify microRNAs (miRs) that inhibit hepatocellular carcinoma (HCC) development in vivo, following miR overexpression in hepatocytes. PB-miRs encoding six different miRs from the miR-17-92 cluster and nine miRs from outside this cluster were transfected into mouse livers that were chemically induced to develop HCC. In this slow-onset HCC model, miR-20a significantly inhibited HCC. Next, we developed a more aggressive HCC model by overexpression of oncogenic Harvey rat sarcoma viral oncogene homolog (HRAS G12V ) and c-MYC oncogenes that accelerated HCC development after only 6 weeks. The tumor suppressor effect of miR-20a could be demonstrated even in this rapid-onset HRAS G12V /c-MYC HCC model, consistent with significantly prolonged survival and decreased HCC tumor burden. Comprehensive RNA expression profiling of 95 selected genes typically associated with HCC development revealed differentially expressed genes and functional pathways that were associated with miR-20a-mediated HCC suppression. To our knowledge, this is the first study establishing a direct causal relationship between miR-20a overexpression and liver cancer inhibition in vivo. Moreover, these results demonstrate that hepatocyte-specific hyPB transposons are an efficient platform to screen and identify miRs that affect overall survival and HCC tumor regression., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)