Regulation of human RNase-L by the miR-29 family reveals a novel oncogenic role in chronic myelogenous leukemia

Endonucleolytic RNA cleavage drives changes in gene expression during the innate immune response

Viral infection triggers several double-stranded RNA (dsRNA) sensors that lead to changes in gene expression in the cell. One of these sensors activates an endonuclease, ribonuclease L (RNase L), that cleaves single-stranded RNA. However, how the resultant widespread RNA fragmentation affects gene expression is not fully understood. Here, we show that this fragmentation induces the ribotoxic stress response via ZAKα, potentially through stalled ribosomes and/or ribosome collisions. The p38 and JNK pathways that are activated as part of this response promote outcomes that inhibit the virus, such as programmed cell death. We also show that RNase L limits the translation of stress-responsive genes. Intriguingly, we found that the activity of the generic endonuclease, RNase A, recapitulates many of the same molecular phenotypes as activated RNase L, demonstrating how widespread RNA cleavage can evoke an antiviral program.

Endonucleolytic RNA cleavage drives changes in gene expression during the innate immune response

Viral infection triggers several dsRNA sensors that lead to changes in gene expression in the cell. One of these sensors activates an endonuclease, RNase L, that cleaves single stranded RNA. However, how the resultant widespread RNA fragmentation affects gene expression is not fully understood. Here we show that this fragmentation induces the Ribotoxic Stress Response via ZAKα, potentially through ribosome collisions. The p38 and JNK pathways that are activated as part of this response promote outcomes that inhibit the virus, such as programmed cell death. We also show that RNase L limits the translation of stress-responsive genes, including antiviral IFIT mRNAs and GADD34 that encodes an antagonist of the Integrated Stress Response. Intriguingly, we found the activity of the generic endonuclease, RNase A, recapitulates many of the same molecular phenotypes as activated RNase L, demonstrating how widespread RNA cleavage can evoke an antiviral program.

Activation of the antiviral factor RNase L triggers translation of non-coding mRNA sequences

Ribonuclease L (RNase L) is activated as part of the innate immune response and plays an important role in the clearance of viral infections. When activated, it endonucleolytically cleaves both viral and host RNAs, leading to a global reduction in protein synthesis. However, it remains unknown how widespread RNA decay, and consequent changes in the translatome, promote the elimination of viruses. To study how this altered transcriptome is translated, we assayed the global distribution of ribosomes in RNase L activated human cells with ribosome profiling. We found that RNase L activation leads to a substantial increase in the fraction of translating ribosomes in ORFs internal to coding sequences (iORFs) and ORFs within 5' and 3' UTRs (uORFs and dORFs). Translation of these alternative ORFs was dependent on RNase L's cleavage activity, suggesting that mRNA decay fragments are translated to produce short peptides that may be important for antiviral activity.

AKR1C3 decreased CML sensitivity to Imatinib in bone marrow microenvironment via dysregulation of miR-379-5p

BACKGROUND

Drug resistance is an important cause of death for most patients with chronic myeloid leukemia (CML). The bone marrow microenvironment is believed to be mainly responsible for resistance to BCR-ABL tyrosine kinase inhibitors. The mechanism involved, however, is still unclear.

METHODS

Bioinformatic analysis from GEO database of AKR1C3 was utilized to identify the AKR1C3 expression in CML cells under bone marrow microenvironment. Western blot and qPCR were performed to detect the AKR1C3 expression in two CML cell lines K562 and KU812 cultured +/- bone microenvironment derived stromal cells. CCK-8, soft agar colony assay, and Annexin V/PI assay were performed to detect the sensitivity of CML cells (K562 and KU812) to Imatinib under a gain of or loss of function of AKR1C3 treatment. The CML murine model intravenous inoculated with K562-OE-vector and K562-OE-AKR1C3 cells were established to estimate the effect of AKR1C3 inhibitor Indomethacin on Imatinib resistance. The bioinformatic analysis of miRNA databases was used to predict the potential miRNAs targeting AKR1C3. And the luciferase assay was utilized to validate the target relationship between miR-379-5p and AKR1C3. And, the soft agar colony assay and Annexin V/PI were used to validate the effect of miR-379-5p in AKR1C3 induced Imatinib resistance.

RESULTS

In present study, we investigated AKR1C3 was highly expressed in CML under bone marrow microenvironment. AKR1C3 decreased Imatinib activity in K562 and KU812 cells, while inhibition of AKR1C3 could enhance Imatinib sensitivity in vitro study. Furthermore, murine model results showed combination use of AKR1C3 inhibitor Indomethacin effectively prolong mice survival, indicating that AKR1C3 is a promising target to enhance Imatinib treatment. Mechanically, AKR1C3 was found to be suppressed by miR-379-5p, which was down-expression in bone marrow microenvironment. Besides, we found miR-379-5p could bind AKR1C3 3'UTR but not degrade its mRNA level. Further, gain of miR-379-5p rescued the imatinib resistance induced by AKR1C3 overexpression in CML cells.

CONCLUSIONS

Altogether, our study identifies a novel signaling regulation of miR-379-5p/AKR1C3/EKR axis in regulating IM resistance in CML cell, and provides a scientific base for exploring AKR1C3 as a biomarker in impeding IM resistance in CML.

Evaluation of the Anticancer Activity of pH-Sensitive Polyketal Nanoparticles for Acute Myeloid Leukemia

Polyketals are a class of acid-responsive polymers that have been relatively less explored for drug delivery applications compared to polyesters. The degradation of these polymers is accelerated in an acidic medium and does not result in acidic byproducts. Their biocompatibility depends on the diol used for the synthesis. The present work aims to synthesize, characterize, and fabricate nanospheres of an aliphatic polyketal for delivery of the nucleotide analogue cytarabine toward the treatment of acute myeloid leukemia (AML). The internalization mechanism of the nanospheres was probed, and its implication on the nuclear localization and escape from the endo-lysosomal compartments were studied. The drug-loaded polyketal nanoparticles reduced the cell viability to a greater extent compared with the free drug. The effect of the drug-loaded polyketal nanoparticles on the differential gene expression of leukemic cells was investigated for the first time to understand their therapeutic implications. It was found that treatment with drug-loaded polyketal nanoparticles downregulated AML-specific genes involved in cell proliferation and recurrence compared to the free drug. The protein expression studies were performed for selected genes obtained from gene expression analysis. Biodistribution studies showed that the poly(cyclohexane-1,4-diyl acetone dimethylene ketal) (PCADK) nanoparticles exhibit prolonged circulation time. Overall, our results suggest that polyketal-based delivery of cytarabine represents a more effective alternative strategy for AML therapy.

MicroRNA-29 family inhibits rhabdomyosarcoma formation and progression by regulating GEFT function

The microRNA-29 family, which contains mir-29a, mir-29b, and mir-29c, can promote or resist the development of several types of tumors. However, its role in rhabdomyosarcoma (RMS) has not been determined. In this work, we detected the expression of mir-29a/b/c in RMS. Results showed that the tissues and cell lines in RMS were significantly lower than those in muscle and human skeletal muscle cells, and that these cell lines could also inhibit the proliferation, migration, and invasion and induce apoptosis of RMS cells. Dual-luciferase reporter assay and RNA immunoprecipitation verified the direct binding site between mir-29a/b/c and GEFT. Under the combined actions of mir-29a/b/c and GEFT, the former weakened the promoting effect of GEFT on RMS cells. Finally, mir-29a inhibited the tumorigenesis of subcutaneous xenografts in nude mice and inhibited the mRNA and protein expression levels of GEFT in transplanted tumors. These findings proved that mir-29 inhibits the occurrence of RMS and may be a potential molecular target.

Antiviral RNAi in Insects and Mammals: Parallels and Differences

The RNA interference (RNAi) pathway is a potent antiviral defense mechanism in plants and invertebrates, in response to which viruses evolved suppressors of RNAi. In mammals, the first line of defense is mediated by the type I interferon system (IFN); however, the degree to which RNAi contributes to antiviral defense is still not completely understood. Recent work suggests that antiviral RNAi is active in undifferentiated stem cells and that antiviral RNAi can be uncovered in differentiated cells in which the IFN system is inactive or in infections with viruses lacking putative viral suppressors of RNAi. In this review, we describe the mechanism of RNAi and its antiviral functions in insects and mammals. We draw parallels and highlight differences between (antiviral) RNAi in these classes of animals and discuss open questions for future research.

Zebrafish microRNA miR-210-5p inhibits primitive myelopoiesis by silencing foxj1b and slc3a2a mRNAs downstream of gata4/5/6 transcription factor genes

Zebrafish gata4/5/6 genes encode transcription factors that lie on the apex of the regulatory hierarchy in primitive myelopoiesis. However, little is known about the roles of microRNAs in gata4/5/6-regulated processes. Performing RNA-Seq deep sequencing analysis of the expression changes of microRNAs in gata4/5/6-knockdown embryos, we identified miR-210-5p as a regulator of zebrafish primitive myelopoiesis. Knocking down gata4/5/6 (generating gata5/6 morphants) significantly increased miR-210-5p expression, whereas gata4/5/6 overexpression greatly reduced its expression. Consistent with inhibited primitive myelopoiesis in the gata5/6 morphants, miR-210-5p overexpression repressed primitive myelopoiesis, indicated by reduced numbers of granulocytes and macrophages. Moreover, knocking out miR-210 partially rescued the defective primitive myelopoiesis in zebrafish gata4/5/6-knockdown embryos. Furthermore, we show that the restrictive role of miR-210-5p in zebrafish primitive myelopoiesis is due to impaired differentiation of hemangioblast into myeloid progenitor cells. By comparing the set of genes with reduced expression levels in the gata5/6 morphants to the predicted target genes of miR-210-5p, we found that foxj1b and slc3a2a, encoding a forkhead box transcription factor and a solute carrier family 3 protein, respectively, are two direct downstream targets of miR-210-5p that mediate its inhibitory roles in zebrafish primitive myelopoiesis. In summary, our results reveal that miR-210-5p has an important role in the genetic network controlling zebrafish primitive myelopoiesis.

MicroRNAs mediated regulation of MAPK signaling pathways in chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a severe problem throughout the world and requires identification of novel targets for its treatment. This multifactorial disease accounts for about 15% of the all diagnosed leukemia cases. Mitogen-activated protein kinase (MAPK) signaling pathway is crucial for the cell survival and its dysregulation is being implicated in various types of cancers. In here, we have discussed the potential role of various miRNAs that are found involved in regulating the proteins cascades of MAPK signaling pathway associated with CML. An emphasis has been paid to summarize the influence of various miRNAs in elevating or suppressing the expression level of significant proteins such as miR-203, miR-196a, miR-196b, miR-30a, miR-29b, miR-138 in BCR-ABL tyrosine kinase; miR-126, miR-221, miR-128, miR-15a, miR-188-5p, miR-17 in CRK family proteins; miR-155, miR-181a with SOS proteins; miR-155, miR-19a, with KRAS proteins; miR-19a with RAF1 protein; and miR-17, miR-19a, miR-17-92 cluster with MAPK/ERK proteins. In light of ever-increasing importance and ever-widening regulatory roles of miRNAs in cells, we have reviewed the recent progress in the field of miRNAs and have tried to suggest them as controlling targets for various protein cascades of MAPK signaling pathway. An understanding of the supervisory mechanism of MAPK by miRNAs might provide novel targets for treating CML.

Oncogenic kinase fusions: an evolving arena with innovative clinical opportunities

Cancer biology relies on intrinsic and extrinsic deregulated pathways, involving a plethora of intra-cellular and extra-cellular components. Tyrosine kinases are frequently deregulated genes, whose aberrant expression is often caused by major cytogenetic events (e.g. chromosomal translocations). The resulting tyrosine kinase fusions (TKFs) prompt the activation of oncogenic pathways, determining the biological and clinical features of the associated tumors. First reported half a century ago, oncogenic TKFs are now found in a large series of hematologic and solid tumors. The molecular basis of TKFs has been thoroughly investigated and tailored therapies against recurrent TKFs have recently been developed. This review illustrates the biology of oncogenic TKFs and their role in solid as well as hematological malignancies. We also address the therapeutic implications of TKFs and the many open issues concerning their clinical impact.

Regulation of the unfolded protein response by noncoding RNA

Cells are exposed to various intrinsic and extrinsic stresses in both physiological and pathological conditions. To adapt to those conditions, cells have evolved various mechanisms to cope with the disturbances in protein demand, largely through the unfolded protein response (UPR) in the endoplasmic reticulum (ER), but also through the integrated stress response (ISR). Both responses initiate downstream signaling to transcription factors that, in turn, trigger adaptive programs and/or in the case of prolonged stress, cell death mechanisms. Recently, noncoding RNAs, including microRNA and long noncoding RNA, have emerged as key players in the stress responses. These noncoding RNAs act as both regulators and effectors of the UPR and fine-tune the output of the stress signaling pathways. Although much is known about the UPR and the cross talk that exists between pathways, the contribution of small noncoding RNA has not been fully assessed. Herein we bring together and review the current known functions of noncoding RNA in regulating adaptive pathways in both physiological and pathophysiological conditions, illustrating how they operate within the known UPR functions and contribute to diverse cellular outcomes.

Epigenetic dysregulation in chronic myeloid leukaemia: A myriad of mechanisms and therapeutic options

The onset of global epigenetic changes in chromatin that drive tumor proliferation and heterogeneity is a hallmark of many forms of cancer. Identifying the epigenetic mechanisms that govern these changes and developing therapeutic approaches to modulate them, is a well-established avenue pursued in translational cancer medicine. Chronic myeloid leukemia (CML) arises clonally when a hematopoietic stem cell (HSC) acquires the capacity to produce the constitutively active tyrosine kinase BCR-ABL1 fusion protein which drives tumor development. Treatment with tyrosine kinase inhibitors (TKI) that target BCR-ABL1 has been transformative in CML management but it does not lead to cure in the vast majority of patients. Thus novel therapeutic approaches are required and these must target changes to biological pathways that are aberrant in CML - including those that occur when epigenetic mechanisms are altered. These changes may be due to alterations in DNA or histones, their biochemical modifications and requisite 'writer' proteins, or to dysregulation of various types of non-coding RNAs that collectively function as modulators of transcriptional control and DNA integrity. Here, we review the evidence for subverted epigenetic mechanisms in CML and how these impact on a diverse set of biological pathways, on disease progression, prognosis and drug resistance. We will also discuss recent progress towards developing epigenetic therapies that show promise to improve CML patient care and may lead to improved cure rates.

The Role of MicroRNAs in Myeloproliferative Neoplasia

MiRs are 17-25 nucleotide non-coding RNAs. These RNAs target approximately 80% of protein coding mRNAs. MiRs control gene expression and altered expression of them affects the development of cancer. MiRs can function as tumor suppressor via down-regulation of proto-oncogenes and may function as oncogenes by suppressing tumor suppressors. Myeloproliferative neoplasias (formerly known as chronic myeloproliferative disorders) form a class of hematologic malignancies demonstrating the expansion of stem cells in one or more hematopoietic cell lines. CML results from an acquired translocation known as BCR-ABL (Philadelphia chromosome). JAK2V617F mutation is present in over 95% of PV, 55% of ET and 65% of PMF cases. Aberrant expression of miR is associated with myeloproliferative neoplasias, pathogenesis, disease progress and response to treatment. MiRs can also be potential therapeutic targets. CML is mainly treated by tyrosine kinase inhibitors such as Imatinib. In addition, altered function of miRs may be used as a prognostic factor in treatment. Resistance to Imatinib is currently a major clinical problem. The role of a number of miRs has been demonstrated in this resistance. Changing expression pattern of miRs can be effective in response to treatment and inhibition of drug resistance. In this paper, we set out to evaluate the effect of miRs in pathogenesis and treatment of MPN.

miR-29s: a family of epi-miRNAs with therapeutic implications in hematologic malignancies

A wealth of studies has highlighted the biological complexity of hematologic malignancies and the role of dysregulated signal transduction pathways. Along with the crucial role of genetic abnormalities, epigenetic aberrations are nowadays emerging as relevant players in cancer development, and significant research efforts are currently focusing on mechanisms by which histone post-translational modifications, DNA methylation and noncoding RNAs contribute to the pathobiology of cancer. As a consequence, these studies have provided the rationale for the development of epigenetic drugs, such as histone deacetylase inhibitors and demethylating compounds, some of which are currently in advanced phase of pre-clinical investigation or in clinical trials. In addition, a more recent body of evidence indicates that microRNAs (miRNAs) might target effectors of the epigenetic machinery, which are aberrantly expressed or active in cancers, thus reverting those epigenetic abnormalities driving tumor initiation and progression. This review will focus on the broad epigenetic activity triggered by members of the miR-29 family, which underlines the potential of miR-29s as candidate epi-therapeutics for the treatment of hematologic malignancies.

Metformin inhibits tumor growth by regulating multiple miRNAs in human cholangiocarcinoma

The antidiabetic drug metformin exerts antineoplastic effects in many types of malignancies, however the effect of metformin on cholangiocarcinoma (CCA) still remains unclear. In the present study, we investigated that metformin treatment was closely associated with the clinicopathologic characteristics and improved postoperative survival of CCA patients. Metformin inhibited CCA tumor growth by cell cycle arrest in vitro and in vivo. We explored that the expression of six miRNAs (mir124, 182, 27b, let7b, 221 and 181a), which could directly target cell-cycle-regulatory genes, was altered by metformin in vitro and in vivo. These miRNAs were dysregulated in cholangiocarcinoma and promoted the CCA genesis and metformin exactly modulated these carcinogenic miRNAs expression to arrest the cell cycle and inhibit the proliferation. Meanwhile, these miRNAs expression changes correlated with the tumor volume and postoperative survival of CCA patients and could be used to predict the prognosis. Further we confirmed that metformin upregulated Drosha to modulate these miRNAs expression. Our results elucidated that metformin inhibited CCA tumor growth via the regulation of Drosha-mediated multiple carcinogenic miRNAs expression and comprehensive evaluation of these miRNAs expression could be more efficient to predict the prognosis. Moreover, metformin might be a quite promising strategy for CCA prevention and treatment.

The Roles of RNase-L in Antimicrobial Immunity and the Cytoskeleton-Associated Innate Response

The interferon (IFN)-regulated endoribonuclease RNase-L is involved in multiple aspects of the antimicrobial innate immune response. It is the terminal component of an RNA cleavage pathway in which dsRNA induces the production of RNase-L-activating 2-5A by the 2′-5′-oligoadenylate synthetase. The active nuclease then cleaves ssRNAs, both cellular and viral, leading to downregulation of their expression and the generation of small RNAs capable of activating retinoic acid-inducible gene-I (RIG-I)-like receptors or the nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome. This leads to IFNβ expression and IL-1β activation respectively, in addition to broader effects on immune cell function. RNase-L is also one of a growing number of innate immune components that interact with the cell cytoskeleton. It can bind to several cytoskeletal proteins, including filamin A, an actin-binding protein that collaborates with RNase-L to maintain the cellular barrier to viral entry. This antiviral activity is independent of catalytic function, a unique mechanism for RNase-L. We also describe here the interaction of RNase-L with the E3 ubiquitin ligase and scaffolding protein, ligand of nump protein X (LNX), a regulator of tight junction proteins. In order to better understand the significance and context of these novel binding partners in the antimicrobial response, other innate immune protein interactions with the cytoskeleton are also discussed.

Potential roles of microRNA-29a in the molecular pathophysiology of T-cell acute lymphoblastic leukemia

Recent evidence has shown that deregulated expression of members of the microRNA-29 (miR-29) family may play a critical role in human cancer, including hematological malignancies. However, the roles of miR-29 in the molecular pathophysiology of T-cell acute lymphoblastic leukemia (T-ALL) has not been investigated. Here, we show that lower levels of miR-29a were significantly associated with higher blast counts in the bone marrow and with increased disease-free survival in T-ALL patients. Furthermore, miR-29a levels are extremely reduced in T-ALL cells compared to normal T cells. Microarray analysis following introduction of synthetic miR-29a mimics into Jurkat cells revealed the downregulation of several predicted targets (CDK6, PXDN, MCL1, PIK3R1, and CXXC6), including targets with roles in active and passive DNA demethylation (such as DNMT3a, DNMT3b, and members of the TET family and TDG). Restoring miR-29a levels in Jurkat and Molt-4 T-ALL cells led to the demethylation of many genes commonly methylated in T-ALL. Overall, our results suggest that reduced miR-29a levels may contribute to the altered epigenetic status of T-ALL, highlighting its relevance in the physiopathology of this disease.

The implication of cancer progenitor cells and the role of epigenetics in the development of novel therapeutic strategies for chronic myeloid leukemia

SIGNIFICANCE

Chronic myeloid leukemia (CML) involves the malignant transformation of hematopoietic stem cells, defined largely by the Philadelphia chromosome and expression of the breakpoint cluster region-Abelson (BCR-ABL) oncoprotein. Pharmacological tyrosine kinase inhibitors (TKIs), including imatinib mesylate, have overcome limitations in conventional treatment for the improved clinical management of CML.

RECENT ADVANCES

Accumulated evidence has led to the identification of a subpopulation of quiescent leukemia progenitor cells with stem-like self renewal properties that may initiate leukemogenesis, which are also shown to be present in residual disease due to their insensitivity to tyrosine kinase inhibition.

CRITICAL ISSUES

The characterization of quiescent leukemia progenitor cells as a unique cell population in CML pathogenesis has become critical with the complete elucidation of mechanisms involved in their survival independent of BCR-ABL that is important in the development of novel anticancer strategies. Understanding of these functional pathways in CML progenitor cells will allow for their selective therapeutic targeting. In addition, disease pathogenesis and drug responsiveness is also thought to be modulated by epigenetic regulatory mechanisms such as DNA methylation, histone acetylation, and microRNA expression, with a capacity to control CML-associated gene transcription.

FUTURE DIRECTIONS

A number of compounds in combination with TKIs are under preclinical and clinical investigation to assess their synergistic potential in targeting leukemic progenitor cells and/or the epigenome in CML. Despite the collective promise, further research is required in order to refine understanding, and, ultimately, advance antileukemic therapeutic strategies.

RNase-L control of cellular mRNAs: roles in biologic functions and mechanisms of substrate targeting

RNase-L is a mediator of type 1 interferon-induced antiviral activity that has diverse and critical cellular roles, including the regulation of cell proliferation, differentiation, senescence and apoptosis, tumorigenesis, and the control of the innate immune response. Although RNase-L was originally shown to mediate the endonucleolytic cleavage of both viral and ribosomal RNAs in response to infection, more recent evidence indicates that RNase-L also functions in the regulation of cellular mRNAs as an important mechanism by which it exerts its diverse biological functions. Despite this growing body of work, many questions remain regarding the roles of mRNAs as RNase-L substrates. This review will survey known and putative mRNA substrates of RNase-L, propose mechanisms by which it may selectively cleave these transcripts, and postulate future clinical applications.

MicroRNAs in virus-induced tumorigenesis and IFN system

Numerous microRNAs (miRNAs), small non-coding RNAs encoded in the human genome, have been shown to be involved in cancer pathogenesis and progression. There is evidence that some of these miRNAs possess proapoptotic or proliferation promoting roles in the cell by negatively regulating target mRNAs. Oncogenic viruses are able to produce persistent infection, favoring tumor development by deregulating cell proliferation and inhibiting apoptosis. It has been recently suggested that cellular miRNAs may participate in host-virus interactions, influencing viral replication. Many mammalian viruses counteract this cellular antiviral defense by using viral proteins but also by encoding viral miRNAs involved in virus-induced tumorigenesis. Interferons (IFNs) modulate a number of non-coding RNA genes, especially miRNAs, that may be used by mammalian organisms as a mechanism of IFN system to combat viral infection and related diseases. In particular, IFNs might induce specific cellular miRNAs that target viral transcripts thereby using this strategy as part of their effectiveness against invading viruses. Therefore IFNs, interferon stimulated genes and miRNAs could act synergistically as innate response to virus infection to induce a potent non-permissive cellular environment for virus replication and virus-induced cancer. The relevance of this reviewed research topic is clearly related to the observation that although virus infections are responsible of specific tumors, other unidentified genetic alterations are likely involved in the induction of malignant transformation. The identification of such genetic alterations, i.e. miRNA expression in transformed cells, would be of considerable importance for the analysis of the pathogenesis and for the treatment of cancer induced by specific viruses as well as for the advancement of the current knowledge on the molecular mechanisms underlying virus-host interaction. In this respect, we will review also the important, still little explored, roles of miRNAs acting both as IFN-stimulated anti-viral molecules and as critical regulators of IFNs and IFN-stimulated genes.

Altered expression pattern of miR-29a, miR-29b and the target genes in myeloid leukemia

Objectives

The miR-29 family have been demonstrated acting as vital tumor suppressor in multiple cancers as well as regulators in the adaptive immune system. Little is known about their role in leukemogenesis. The purpose of this study is to analyze the expression pattern of miR-29a/29b and its target genes Mcl-1 (myeloid cell leukemia sequence 1) and B-cell lymphoma 2 (Bcl-2) in myeloid leukemia.

Methods

Quantitative real-time PCR was used for detecting genes expression level in peripheral blood mononuclear cells (PBMCs) from 10 cases with newly diagnosed, untreated acute myeloid leukemia (AML) and 14 cases with newly diagnosed, untreated chronic myeloid leukemia (CML) in chronic phase, and 14 healthy individual (HI) served as controls. Correlation between the relative expression levels of different genes have been analyzed.

Results

Significant lower expression of miR-29a/29b and higher expression level of two potential target genes Bcl-2 and Mcl-1 were found in PBMCs from AML and CML patients compared with HI group. In addtion, miR-29a expression in AML was significantly lower than that in CML. Moreover, negative correlation between miR-29a/29b and its target genes have been found. While, positive correlation between relative expression level of miR-29a and miR-29b or Bcl-2 and Mcl-1 were presented in the total 38 research objects.

Conclusion

Down-regulated miR-29a and miR-29b, and accompanying up-regulated Bcl-2 and Mcl-1 are the common feature in myeloid leukemias. These data further support the role for miR-29a/29b dysregulation in myeloid leukemogenesis and the therapeutic promise of regulating miR-29a/29b expression for myeloid leukemia in the future.

The role of miR-29 family members in malignant hematopoiesis

AIMS

MicroRNAs of the miR-29 family members were one of the first microRNAs identified as possible therapeutic agents in malignant hematopoiesis. The aim of our review is to summarize the current state of knowledge on miR-29 family members.

METHODS

We performed literature searches involving miR-29 family members and their relationship to individual hematological malignancies, namely acute myeloid leukemia (AML), chronic lymphoblastic leukemia (CLL) and chronic myeloid leukemia (CML). We also searched for subgroups of hematological malignancies, e.g. multiple myeloma, that are regarded as members of the acute or chronic types of leukemias.

RESULTS

A number of genes appear to be regulated by miR-29 family members in various physiological and pathological situations. In our view regulation of Tcl-1, Mcl-1 and DNA methyltransferases is relevant in case of hematological malignancies, hence these are the focus of this review. miR-29 family members also function during normal T-cell and B-cell development.

CONCLUSION

MiR-29 family members appear to govern some general features in commonly heterogenous hematological malignancies and therefore form a potential target for treatment.

Can't RIDD off viruses

The mammalian genome has evolved to encode a battery of mechanisms, to mitigate a progression in the life cycle of an invasive viral pathogen. Although apparently disadvantaged by their dependence on the host biosynthetic processes, an immensely faster rate of evolution provides viruses with an edge in this conflict. In this review, I have discussed the potential anti-virus activity of inositol-requiring enzyme 1 (IRE1), a well characterized effector of the cellular homeostatic response to an overloading of the endoplasmic reticulum (ER) protein-folding capacity. IRE1, an ER-membrane-resident ribonuclease (RNase), upon activation catalyses regulated cleavage of select protein-coding and non-coding host RNAs, using an RNase domain which is homologous to that of the known anti-viral effector RNaseL. The latter operates as part of the Oligoadenylate synthetase OAS/RNaseL system of anti-viral defense mechanism. Protein-coding RNA substrates are differentially treated by the IRE1 RNase to either augment, through cytoplasmic splicing of an intron in the Xbp1 transcript, or suppress gene expression. This referred suppression of gene expression is mediated through degradative cleavage of a select cohort of cellular RNA transcripts, initiating the regulated IRE1-dependent decay (RIDD) pathway. The review first discusses the anti-viral mechanism of the OAS/RNaseL system and evasion tactics employed by different viruses. This is followed by a review of the RIDD pathway and its potential effect on the stability of viral RNAs. I conclude with a comparison of the enzymatic activity of the two RNases followed by deliberations on the physiological consequences of their activation.

RNASEL and MIR146A SNP-SNP interaction as a susceptibility factor for non-melanoma skin cancer

Immunity and inflammatory pathways are important in the genesis of non-melanoma skin cancers (NMSC). Functional genetic variation in immune modulators has the potential to affect disease etiology. We investigated associations between common variants in two key regulators, MIR146A and RNASEL, and their relation to NMSCs. Using a large population-based case-control study of basal cell (BCC) and squamous cell carcinoma (SCC), we investigated the impact of MIR146A SNP rs2910164 on cancer risk, and interaction with a SNP in one of its putative targets (RNASEL, rs486907). To examine associations between genotype and BCC and SCC, occurrence odds ratios (OR) and 95% confidence intervals (95%CI) were calculated using unconditional logistic regression, accounting for multiple confounding factors. We did not observe an overall change in the odds ratios for SCC or BCC among individuals carrying either of the RNASEL or MIR146A variants compared with those who were wild type at these loci. However, there was a sex-specific association between BCC and MIR146A in women (ORGC = 0.73, [95%CI = 0.52-1.03]; ORCC = 0.29, [95% CI = 0.14-0.61], p-trend<0.001), and a reduction in risk, albeit not statistically significant, associated with RNASEL and SCC in men (ORAG = 0.88, [95%CI = 0.65-1.19]; ORAA = 0.68, [95%CI = 0.43-1.08], p-trend = 0.10). Most striking was the strong interaction between the two genes. Among individuals carrying variant alleles of both rs2910164 and rs486907, we observed inverse relationships with SCC (ORSCC = 0.56, [95%CI = 0.38-0.81], p-interaction = 0.012) and BCC (ORBCC = 0.57, [95%CI = 0.40-0.80], p-interaction = 0.005). Our results suggest that genetic variation in immune and inflammatory regulators may influence susceptibility to NMSC, and novel SNP-SNP interaction for a microRNA and its target. These data suggest that RNASEL, an enzyme involved in RNA turnover, is controlled by miR-146a and may be important in NMSC etiology.

Diverse roles of miR-29 in cancer (review)

microRNAs (miRNAs) are non-coding RNAs which have the capacity to regulate gene expression at the post-transcriptional level, and have emerging as key factors involved in cancer at all stages ranging from initiation to metastasis. In the present review, we summmarize the diverse roles of the microRNA-29 (miR-29) family in cancer. First, we present a concise introduction to the miR-29 family and the expression profile of miR-29 in various cancer types. We next highlight the upstream regulatory pathway of miR-29 and describe the relationship between miR-29 and cancer in detail. As a tumor suppressor, miR-29 restrains cancer progression by promoting tumor cell apoptosis, by suppressing DNA methylation of tumor-suppressor genes, by reducing proliferation of tumors and by increasing chemosensitivity. However, as a tumor promoter, miR-29 mediates epithelial-mesenchymal transition (EMT) and promotes metastasis in breast cancer and colon cancer. Finally, we suggest that miR-29 represents a novel diagnostic and prognostic biomarker or a therapeutic target for cancer. Our review highlights the diverse relationship between miR-29 and cancer (particularly digestive system neoplasms). Further research of miR-29 in cancer is warranted.

Reciprocal inhibition between intracellular antiviral signaling and the RNAi machinery in mammalian cells

RNA interference (RNAi) is an established antiviral defense mechanism in plants and invertebrates. Whether RNAi serves a similar function in mammalian cells remains unresolved. We find that in some cell types, mammalian RNAi activity is reduced shortly after viral infection via poly-ADP-ribosylation of the RNA-induced silencing complex (RISC), a core component of RNAi. Well-established antiviral signaling pathways, including RIG-I/MAVS and RNaseL, contribute to inhibition of RISC. In the absence of virus infection, microRNAs repress interferon-stimulated genes (ISGs) associated with cell death and proliferation, thus maintaining homeostasis. Upon detection of intracellular pathogen-associated molecular patterns, RISC activity decreases, contributing to increased expression of ISGs. Our results suggest that, unlike in lower eukaryotes, mammalian RISC is not antiviral in some contexts, but rather RISC has been co-opted to negatively regulate toxic host antiviral effectors via microRNAs.

microRNA control of interferons and interferon induced anti-viral activity

Interferons (IFNs) are cytokines that are spontaneously produced in response to virus infection. They act by binding to IFN-receptors (IFN-R), which trigger JAK/STAT cell signalling and the subsequent induction of hundreds of IFN-inducible genes, including both protein-coding and microRNA genes. IFN-induced genes then act synergistically to prevent virus replication and create an anti-viral state. miRNA are therefore integral to the innate response to virus infection and are important components of IFN-mediated biology. On the other hand viruses also encode miRNAs that in some cases interfere directly with the IFN response to infection. This review summarizes the important roles of miRNAs in virus infection acting both as IFN-stimulated anti-viral molecules and as critical regulators of IFNs and IFN-stimulated genes. It also highlights how recent knowledge in RNA editing influence miRNA control of virus infection.

MicroRNAs in myeloid malignancies

MicroRNAs (miRNAs) are key to the pathogenesis of human malignancies and increasingly recognized as potential biomarkers and therapeutic targets. Haematological malignancies, being the earliest human malignancies linked to aberrant miRNA expression, have consistently underpinned our understanding of the role that miRNAs play in cancer development. Here, we review the expanding roles attributed to miRNAs in the pathogenesis of different types of myeloid malignancies and highlight key findings.