Review Article The Potential of MicroRNAs in Personalized...

Review ArticleThe Potential of MicroRNAs in PersonalizedMedicine against Cancers

Anne Saumet1 Anthony Mathelier2 and Charles-Henri Lecellier1234

1 Universite Montpellier 1 5 Bd Henri IV 34967 Montpellier Cedex 2 France2 Centre for Molecular Medicine andTherapeutics at the Child and Family Research InstituteDepartment of Medical Genetics University of British Columbia Vancouver BC Canada V5Z 4H4

3 Institut de Genetique Moleculaire de Montpellier UMR 5535 CNRS 1919 route de Mende 34293 Montpellier Cedex 5 France4Universite Montpellier 2 Place Eugene Bataillon 34095 Montpellier Cedex 5 France

Correspondence should be addressed to Charles-Henri Lecellier charleslecellierigmmcnrsfr

Received 7 June 2014 Accepted 6 August 2014 Published 28 August 2014

Academic Editor Paolo Gandellini

Copyright copy 2014 Anne Saumet et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

MicroRNAs orchestrate the expression of the genome and impact many if not all cellular processes Their deregulation is thusoften causative of human malignancies including cancers Numerous studies have implicated microRNAs in the different steps oftumorigenesis including initiation progression metastasis and resistance to chemoradiotherapies Thus microRNAs constituteappealing targets for novel anticancer therapeutic strategies aimed at restoring their expression or function As microRNAs arepresent in a variety of human cancer types microRNA profiles can be used as tumor-specific signatures to detect various cancers(diagnosis) to predict their outcome (prognosis) and tomonitor their treatment (theranosis) In this reviewwe present the differentaspects of microRNA biology that make them remarkable molecules in the emerging field of personalizedmedicine against cancersand provide several examples of their industrial exploitation

1 Introduction

Recent technological advances in the field of molecularbiology have revolutionized not only basic biological con-cepts but also clinical practice in particular in the field ofanticancer treatment Management of patients with canceris often based on the identification of tumor morphologywhich decides the treatment program a patient shouldbe enrolled in However pan-genomic analyses of geneticand epigenetic alterations and gene expression profiles areproviding important new insights into the pathogenesisand molecular classification of cancers [1] These rapidlydiversifying and improving technologies to analyze tumorshave revealed distinctive genomic (DNA mutations andchromosomal alterations) epigenomic (eg DNA methyla-tion profiles) and transcriptomic (RNA expression profiles)differences between tumors that improve their classificationin distinct molecular subtypes [2] It is rapidly becoming

apparent that each tumor has a unique combination of codingand noncoding mutations that distinguish between patientsrsquotumors and therefore have the potential to serve as ldquosig-naturesrdquo in personalized anticancer therapies It is possibleto tailor patient medical care through the combination ofindividual genomic studies phenotypic histomorphologicalfeatures and patient clinical specificities [3] This approachreferred to as ldquopersonalizedrdquo or ldquoindividualizedrdquo medicineis distinct from the classical ldquogeneralizedrdquo medicine as themedical decisions and selection of optimal therapies arenot indiscriminately applied to each patient but rather takeinto account several parameters that identify the specificstatus of a patient Personalized medicine will improveprediction of susceptibility to diseases and will restrict thedevelopment of cancers by anticipating disease progressionThe use of personalized medicine will also reduce emergenceof chemoresistance through the selection of drugs deemedmost effective for each patient [2 3] This medical strategy

Hindawi Publishing CorporationBioMed Research InternationalVolume 2014 Article ID 642916 10 pageshttpdxdoiorg1011552014642916

2 BioMed Research International

will save time and improve cost effectiveness not to mentionsignificantly improving patientsrsquo quality of life by limiting theadverse effects of inappropriate treatments [2 3]

One prerequisite for the development of personalizedmedicine is the identification of combinations of biomarkersto guide a physicianrsquos clinical decision It is in this context thatthe potential of microRNAs (miRNAs) a particular class ofsmall noncoding RNAs has rapidly become apparent [4ndash6]To date more than two thousand human miRNAs have beenidentified [7] These small RNAs orchestrate the expressionof the genome at the posttranscriptional level and adapt theprotein output to various intracellular or extracellular stimuliAs such they impact many if not all cellular processes andtheir deregulation is causative of many human malignanciesincluding cancers [8ndash11] A plethora of researchers havenow implicated miRNAs in the initiation and progression ofprimary tumors as well as in metastasis formation [12ndash14]More than 12600 publications related to miRNA and cancerare listed in the NCBI PubMed database and their numberexponentially grows Advantageously cancer cell types tendto have a highly specific cellular repertoire of miRNAs [15ndash18] The expression levels of miRNA can be monitored ina variety of human specimens including fresh or formalin-fixed paraffin embedded (FFPE) tissues [19 20] as well asin almost all human body fluids [21ndash25] Moreover recentstudies revealed that specific miRNA expression levels inbiological fluids are associated with chemotherapy responses[23 26 27] Hence in addition to their potential as targets ofnovel anticancer therapies several aspects of miRNA biologymake them excellent candidates as biomarkers to be used ininnovative and noninvasive tests aimed at identifying variouscancers (diagnosis) predicting their outcome (prognosis)and monitoring their treatments (theranosis) [21 25 28ndash31]Here we review the different aspects of miRNA biology thatestablish their potential in the emerging field of personalizedmedicine against cancers We also present several knownlimitations of their exploitation as well as future challengesand ongoing industrial developments

2 miRNA Biogenesis andMechanism of Action

miRNAs are noncoding RNAs typically sim18ndash22 nucleotideslong which are generated through a complex multistepprocess Several excellent reviews have already thoroughlydescribed this process (see [32ndash35]) We focus here on theevents required for the understanding of this review MiRNAgenes are first transcribed by RNA polymerase II into longcapped and polyadenylated primarymiRNAprecursors (pri-miRNAs) The pri-miRNAs are subsequently processed bythe nuclear RNase III enzymeDrosha into precursormiRNAs(pre-miRNAs) [36ndash38] The pre-miRNAs are exported fromthe nucleus to the cytoplasm where they are cleaved by thecytoplasmic RNase III enzyme Dicer into a double-strandedRNA duplex (miR-5pmiR-3p) Alternative pathways existthat bypass either the Drosha or the Dicer steps [39] butthese pathways invariably produce a miR-5pmiR-3p duplexThe two strands of the duplex are then incorporated into the

effector complex called the miRNP complex which containsseveral proteins including the key Argonaute proteins Onestrand of the miRNA duplex then redirects the miRNP ontoRNAs that harbor partial sequence complementarity Thestudy of the mechanisms responsible for the recognitionof RNAs by miRNAs is an intense field of research withrapidly evolving concepts (eg location of miRNA bindingsites [40 41]) Canonical models are based on imperfectbase-pairing between the mature miRNA and the targetedRNA The extent to which the 51015840 end of the mature miRNA(referred to as the ldquoseedrdquo) pairs with the targeted RNA isof particular importance for the efficacy of miRNA-targetinteractions [42] The miRNP complex eventually inducesmRNA degradation andor repression of translation [43 44]While the formerrsquos mechanism relies on deadenylation andfurther exonucleolytic cleavage of the mRNA the latterrsquosremains unclear and is debated as translation repressioncould occur at different steps inhibition of initiation inhi-bition of elongation cotranslational protein degradation orpremature termination of translation [43]

The expression of miRNAs is a tightly regulated processthat is extremely sensitive to intra- and extracellular stimuli(eg hormones vitamins pharmacological molecules orhypoxia) [13 45ndash49] As a consequence each cell type at aparticular time and a particular location harbors a particularmiRNA repertoire This important concept constitutes thebasis of the remarkable interest in miRNAs within the field ofoncology The potential importance of miRNAs to medicinewas first highlighted by the seminal findings of Chen et al[50] who demonstrated that some miRNAs are expressedin hematopoietic cells and showed that their expressionwas dynamically regulated during early hematopoiesis andlineage commitment Importantly they showed that miR-181 was preferentially expressed in the B-lymphoid cells andthat its ectopic expression in hematopoietic stemprogenitorcells led to an increased fraction of B-lineage cells Thus itwas illustrated that it is possible to distinguish different celltypes or different cellular conditions (ie treatment) basedon miRNA profiling Moreover miRNA expression levels insomatic cells of male and female patients can differ likelydue to exposure to specific hormones (eg testosteroneestrogen and androgen) an observation that can explaingender-related differences noted in disease outcome andpathogenesis [51 52] Similarly the expression of somemiRNAs can be linked to aging [53ndash55]The specificity of thecellular miRNA repertoire and its sensitivity to a large panelof intraextracellular stimuli and characteristics (includinggender and age) have stimulated interest not only in basicresearch focused on deciphering the contribution of miRNAsto cancer development but also in more applied researchaimed at evaluatingmiRNAsrsquo potential in cancer personalizedmedicine

3 miRNAs and Cancer

Extensive research has shown that miRNAs play essentialroles in cancer initiation progression and metastasis forma-tion [56ndash59] The miRNA expression levels in tumors canbe up- or downregulated compared to normal tissue and

BioMed Research International 3

several miRNAs have been directly implicated in tumori-genesis by acting either as ldquooncomirsrdquo or tumor suppressormiRNAs [15 60 61] Among them we can cite the miR-17ndash92 cluster (several miRNAs transcribed in a single tran-scription unitpri-miRNA) which was the first oncogenicmiRNA locus described [62] Conversely the miR-34a is animportant miRNAwith tumor suppressor activity which canbe directly transactivated by p53 [60] Its upregulation resultsin increased apoptosis and altered expression of genes relatedto cell cycle progression apoptosis and angiogenesis [63]As observed for protein coding genes [64ndash68] individualmiRNAs can behave as oncogenes in one cell type and astumor suppressors in others [69 70] For example miR-221 acts as an oncogene in liver cancer by downregulatingthe expression of the tumor suppress or phosphatase andtensin homolog (PTEN) but it acts as a tumor suppressorin erythroblastic leukaemia by reducing the expression of theKIT oncogene [69 70] This dual action can be attributed tospecific cellular contexts which expose a miRNA to distincttranscriptional regulation andor to different RNA targets[42 71]

The changes in the miRNA repertoire observed in cancercan result from (1) various disruptive mechanisms occurringat genes (deletions amplifications or mutations of miRNAgenes) (2) regulation of transcription (epigenetic silencingderegulation of transcription factors) or (3) posttranscrip-tional regulation (deregulation of the miRNA biogenesispathway) [13 72 73] One of the first implications of miRNAsin cancer was the discovery that the gene encoding miR-15a and miR-16 is frequently deleted in chronic lymphocyticleukemia [12] This observation was further supported byother miRNA genes in other types of cancers [74ndash76] Thetranscriptional deregulation of miRNA genes is mechanis-tically similar to what is observed in the case of codinggenes and relies on similar processes (DNA methylationhistone acetylation defect in specific transcription factorbinding) [77 78] We have for instance demonstrated thatthe PML-RARA oncogenic protein associated with acutepromyelocytic leukemia represses retinoic acid-responsivemiRNA genes similar to coding genes [79] Likewise inbreast cancer cells the antagonism between RARA and ESR1initially observed in the case of coding genes [80] alsooccurs on miRNA genes [45] The deregulation observed atthe posttranscriptional level (ie biogenesis of miRNA) ismanifestly more specific to miRNAs For instance the LIN28protein a developmentally regulated RNA binding proteinwhose expression is reactivated in many human tumors canspecifically block the Drosha cleavage of the pri-miRNAsbelonging to the let-7 family [81] The expression of severalproteins (eg Dicer Drosha and Argonaute 2) involved inthe biogenesis processing or the action of the miRNAs canbe perturbed in certain cancers with presumably even morebroad impact on cell physiology [82 83] The combinatoricsof varied sources of deregulation generates miRNA profilesare specific to cancer typessubtypes and are often associatedwith staging progression and response to chemotherapies[15ndash18 26 60 84 85] thereby providing a means for thedevelopment ofmiRNA-based diagnostic prognostic andortheranostic tests

4 miRNA and miRNA Target SiteAlterations in Cancer

Alteration of miRNA-mediated posttranscriptional regula-tion can be the consequence of genomic variations spe-cific to cancer Studies have shown that genomic mutationsobserved in cancer cells can drastically perturb miRNA-mediated regulation by modifying either the sequence ofthe miRNAs or the sequence of their targets Intensiveefforts are developed to collect the relevant data and todevelop tools for their analysis The first studies assessingthe impact of mutations on miRNA-mediated regulationfocused on polymorphic mutations (single nucleotide poly-morphism (SNP)) (see [86] for a review) Bioinformaticsstudies highlighted SNPs in cancer samples located in pri-miRNAs pre-miRNA mature miRNAs and miRNA targetswith a potential impact on miRNA biogenesis or the processof miRNA-mediated posttranscriptional regulation [87ndash90]Operating under the knowledge that mRNAs are predomi-nantly targeted by miRNAs in their 31015840UTRs [91] Bruno etal used SNP data to create the miRdSNP database whichstores disease-associated SNPs located in the 31015840UTRs of genesand are supported by the literature after manual curation ofpublications stored in PubMed [92] The most recent versionof miRdSNP (v1103) stores 175351 SNPs in 31015840UTRs with630 disease-associated SNPs for 204 diseases (including sim30cancers) While previous studies have mainly been focusedon SNPs an increasing number of studies provide accessto patient-specific somatic SNVs Last year Bhattacharya etal created SomamiR [93] the first comprehensive databaseof mutations from whole-genome sequencing of cancersamples obtained by extracting mutations specific to cancersamples when compared to matched normal samples Thedatabase provides the community with germline and somaticmutations in miRNAs and target sites that have the potentialto functionally altering miRNA regulation Importantly thedatabase stores experimental information about the impactof the mutations on miRNA function and their associationwith cancer

Bioinformatics analyses of SNVs in miRNA target sitesare critical for predicting functionally impactful mutationsbut the development of bioinformatics approaches has onlyrecently started to be the focus of concerted genomewideefforts By combining whole-genome sequencing data fromThe Cancer Genome Atlas pan-cancer data set with Arg-onaute crosslink immunoprecipitation (AGO-CLIP) dataHamilton et al [94] defined a set of miRNA target sitesderived from AGO-CLIP that were mutated in cancer Thealgorithm developed by Hamilton et al was then usedto identify thousands of SNVs in miRNA binding sitesBy combining these datasets with mRNA expression theyhighlighted expression changes correlating with mutationsFour out of six tested mutations successfully exhibited exper-imentally strong evidence of miRNA binding and regula-tion An alternative approach for highlighting mutationsthat impact miRNA regulation is through analyses of thetranscriptome In [95] the authors identified 73717 SNVs inUTRs from transcriptome data of non-small-cell lung cancersamplesThis set of SNVs was processed to predict mutations


affecting miRNA secondary structure and target sites Thecomputational analysis highlighted 490 SNVs with potentialeffects onmiRNA target sites the SNVs in turn are associatedwith genes enriched in molecular mechanisms of cancerIn the recent years it has become apparent that mutationsin miRNAs and miRNA target sites that play a criticalrole in cancer development As an increasing number ofcancerwhole-genome sequence datasets will become publiclyavailable to the community in the near future it is critical todevelop dedicated computational tools for the identificationof mutations altering miRNA-mediated regulation This willenable the community to better understand the underlyingcauses of carcinogenesis at the level of miRNA regulationand promises to significantly contribute to the vision ofpersonalized diagnosis and therapeutic treatment

5 miRNA-Based Cancer Diagnosis

While cancer-specific mutations in miRNA genes andortheir targets can be detected by classical DNA sequencingtechnologies miRNA expression profiling requires morespecific approaches Three types of miRNA profiling tech-nologies are currently used RT-qPCRmicroarrays andRNAsequencing The RT-qPCR approach requires a particularreverse transcription step which is primed by a stem-loopoligonucleotide [96] This primer can pair with the 31015840 regionof the mature miRNA or with an adapter than have beenligated to its 31015840 end This latter solution allows the use of onesingle RT primer while adding a ligation step The PCR stepcan rely on either the Taqman or SYBRGreen technologyTheRT-qPCR does not necessitate large amounts of RNA andis traditionally recognized as highly sensitive and specificSeveral assays are commercially available either in a specificsingle miRNA format or as arrays that can correspond tohundreds of miRNAs (this number is limited by the platesused for qPCR) Conversely microarrays can detect moremiRNAs in one single experiment but this approach isconsidered to be less specific BothRT-qPCRandmicroarraysare targeted technologies that do not allow the detectionof novel miRNAs that are constantly identified [97 98]As an alternative RNA sequencing is obviously the mostpowerful profiling technology in terms of both specificity andsensibility but its cost is still high (compared to RT-qPCRor microarray) and the data generated require substantialcomputational processing

In addition to intracellular expression miRNAs can bedetected in extracellular compartments The presence ofspecific extracellular and circulating miRNAs in several bodyfluids of cancer patients is now largely described [21 2225] These circulating miRNAs are particularly interesting inthe context of personalized medicine because correlationsbetween high levels of specific circulating miRNAs andthe response to a given anticancer treatment have beenobserved [26 88 99] For instance levels of miR-21 werefound elevated in the serum of patients suffering frommetastatic hormone-refractory prostate cancer especially inthose patients resistant to docetaxel-based chemotherapy[27] Studies in gastric and bladder cancers also identifiedspecific miRNAs involved in cisplatin resistance [100ndash102]

Although the molecular basis behind the secretion of miR-NAs remains largely unknown it appears to be specific Thesecretion ofmiRNAs represents a potentmode of intercellularcommunication that can for instance create a favorablecontext for the implantation of metastasis and the formationof secondary tumors [99 103] The miRNAs circulating inbody fluids also present the remarkable characteristic ofbeing extremely stable though the mechanistic basis of thisresistance to degradation remains largely unclear [104] Onereason could lie in the fact that circulating miRNAs arepackaged in exosomes or other microvesicles present in bodyfluids as well as associated with (lipo)proteins (HDL andArgonaute 2) [105ndash107]

Similar to mutations several miRNA profiles in varioushuman specimens and cancers have been collected and madepublicly available in dedicated databases PhenomiR [108]oncomiRDB [61] PROGmiR [109] miRo [110] and miRan-dola [111] We acknowledge that revisiting these data candampen enthusiasm for the diagnosticprognostic potentialof miRNAs [112 113] In fact no matter the technologyused or the tissue studied several issues associated withstandardization of samplesmanipulationmiRNAs extractionprotocols measurements and statistical analyses still requireimprovements [114ndash116] Several papers have previously tack-led the importance of samples processing [117 118] For exam-ple hemolysis occurring during blood collection can havesignificant impact onmiRNAprofiling in plasmaserum [119ndash122] The evaluation of the quantity and quality of miRNAsisolated from biological samples is indeed a key step inmiRNA profiling Although methods for miRNA extractionare usually similar to that used in the case of total RNAs(with possibly only slight modifications required to retainthe small RNA fraction) the sizes and relative abundance ofribosomal RNAs cannot give information about the integrityof the miRNA preparation In addition the quantificationof miRNA preparations can only be accurate in sampleswhere larger RNAs are not degraded as the degradationproducts can compromise this quantification Moreover thelow concentration of RNAs present in certain body fluidsmakes the estimation of miRNAs abundance particularlydifficult [123] The measurement of miRNA expression canalso be affected by certain compounds coextractedwithRNAs[124] Strikingly it has been reported that short RNAs withlow GC content may be selectively lost during extractiondepending on the extraction methods [125] In addition tothese experimental steps data standardization and normal-ization as well as the evaluation of their statistical significancemust also be carefully defined

Overall it is likely that inconsistencies in any of the stepsdescribed above will impede the definition of robust cancer-specific miRNA signatures [112 113] but a better definitionand standardization of the protocols used will undoubtedlyovercome these obstacles [104 126] Several companies haveindeed decided to meet the challenge (eg Santaris PharmaRosetta Genomics Cepheid Prestizia-Theradiag and Inte-graGen [127]) These efforts have for instance revealed thatthe expression level of the miR-31-3p allows the identificationof patients with wild-type KRAS metastatic colorectal cancerresponding to anti-EGFR therapy [128] With approximately


two-thirds of metastatic colorectal cancer patients beingwild-type KRAS this marker could help better use EGFRtherapy and spare patients from inappropriate treatment

6 miRNA-Based Anticancer Therapy

It is important to note that miRNA deregulations observedin cancers are not necessarily involved in carcinogenesis butthat such deregulation could constitute potent biomarkersnonetheless In contrast some miRNAs have been trulyfunctionally implicated in the developmentprogression ofcancer or in the integration of chemotherapies In thatspecific case miRNAs can represent appealing candidatetargets for novel anticancer therapies [129ndash131] In fact somepharmaceutical companies are already finalizing preclinicalresearch phases and proceeding to clinical trials (see below)In addition to pharmacological agents classically used inoncology and able to control transcription and miRNAexpression [132 133] two miRNA-specific technologicalapproaches can be envisaged (i) to downregulate or block thefunction of oncogenicmiRNAs (miRNA antagonists) and (ii)to upregulate the expression of miRNAs that have a tumor-suppressive function (miRNA mimics) The ultimate goal ofthese manipulations would be to restore a nonpathogenicmiRNA profile [129ndash131] but even more interesting in thecontext of personalized medicine they can also sensitizecancerous cells to a particular chemoradiotherapy In factsomemiRNAs are implicated in the integration of drug effect[100ndash102] and modulating these miRNAs would restore thesensitivity of drug-resistant cells to chemotherapy and wouldprevent tumor recurrence [134 135] as exemplified in the caseof microRNA-200c [136]

Current strategies to inhibit miRNAs aremainly based onantisense oligonucleotides (also known as anti-miRs includ-ing locked nucleic acids (LNA anti-miRs) tiny LNA anti-miRs and antagomirs) which titer the targeted miRNA [137ndash140] They usually involve the introduction of a chemicallymodified single stranded RNA that binds with high affinity toa miRNA of interest Since pairing with the inhibitor is verystable the targeted miRNA is unable to repress translationLNA-mediated miRNA silencing was shown to be efficientin vivo even in non-human primates [141] In fact an LNA-based inhibitor of miR-122 miravirsen is currently beingtested in phase 2 clinical trials for the treatment of hepatitis Cvirus infection [142] Another strategy used to inhibitmiRNAis to introduce within the cells an artificial RNA decoyalso called miRNA sponge which harbors several bindingsites complementary to a miRNA of interest [143ndash145] ThismiRNA sponge can be produced from a transgene allowingstable expression even in vivo [143] It is interesting to notethat this artificial strategy is in fact an endogenous regulatoryprocess which involves long non-coding RNAs referred toas competing endogenous RNAs (ceRNAs) acting as miRNAsponges [146] Whether this situation is widely encounteredand could occur with different long noncoding RNAs is stilldebated [147] but similar strategies have also been describedin the case herpesvirus saimiri which produces an RNAdecoy able to titer the miR-27 [148] In addition to nucleic-acid based strategies (ie anti-miRs and miRNA sponges)

small chemical molecules able to block the processing of thepre-miRNAs by Dicer are also envisaged [149]

On the other hand artificial restoration of the expressionor function of one or a limited number of miRNAs alsocalled ldquomiRNA replacement therapyrdquo can be achieved eitherwith miRNA mimics (typically introduced in the cell as pre-miRNAs) or with miRNAs directly encoded by expressionvectors In many cases the reintroduction of these miRNAsleads to a reactivation of pathways that are required fornormal cellular function [150 151] It is worth mentioningthat a clinical trial using a miR-34 mimic is already inprogress [152 153] In preclinical studies it was reportedthat the injection of miR-34a mimic extended the survivalof tumor-bearing mice [58] Another study demonstratedthat systemic administration of a miR-34 in a pancreaticxenograft cancer model significantly inhibited tumor growthand induced cancer cell apoptosis [154] In May 2013 theMirna Therapeutics Company initiated a phase I study toevaluate the safety of MRX34 a liposome-formulated mimicof miR-34 in patients with unresectable primary liver cancerand advanced or metastatic cancer (ClinicalTrialsgov Identi-fier NCT01829971) Likewise let-7 mimics are in preclinicaldevelopment stages at MirnaTherapeutics

In addition to these chemical and synthetic proceduresmiRNAexpression levels can also be adjusted through dietarymanipulations Several nutrients such as amino acids car-bohydrates fatty acids vitamins and phytochemicals (cur-cumin resveratrol) are indeed known to modulate miRNAexpression levels [155 156] For instance intake of dietaryfiber is inversely associated with colorectal cancer risk [157]The microbial anaerobic fermentation of dietary fiber pro-duces short chain fatty acids (such as acetate propionateand butyrate) and butyrate whose bioavailability is reducedin case of low fiber intake was shown to decrease theexpression of several oncogenic miRNAs in HCT-116 (miRs-17 -20a -20b -93 -106a and -106b) [158] Hence althoughfurther studies are required to fully unveil the mechanismsunderlying diet-mediated miRNA regulations modulatingfood intakemay contribute to novelmiRNA-based anticancerstrategies that could be easily adapted to patientrsquos require-ments

7 Conclusion

Thediscovery ofmiRNAs and their implication in cancer hasnot only intensified the ldquononcoding RNA revolutionrdquo [159]but also opened up new prospects in biomarker and thera-peutic target studies [26 27] These molecules harbor spe-cific features (stability easy manipulation reasonably simpledetection and tissue specificity) that can guide individualizedtreatments and monitoring of cancers Some limits still existthat may prevent their immediate large-scale exploitationbut collective efforts currently made by both academic andindustrial researchers will certainly circumvent these con-straints and rapidly transfer miRNAs from bench to bedsideWe also anticipate that this particular field of research andthe field of personalized medicine as a whole will encourage(not to say demand) the acquisition of novel expertiseand competences by physicians in order to understand and


combine computationalexperimental biology together withmedical practices

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors thank Rebecca Worsley Hunt for critical read-ing of the paper They are grateful to Wyeth W Wasser-man for continuous support and acknowledge the GenomeCanadaGenome BC for funding (ABC4DE Project)

References

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[7] A Kozomara and S Griffiths-Jones ldquomiRBase annotating highconfidence microRNAs using deep sequencing datardquo NucleicAcids Research vol 42 pp D68ndashD73 2013

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[10] M Ghildiyal and P D Zamore ldquoSmall silencing RNAs anexpanding universerdquoNature Reviews Genetics vol 10 no 2 pp94ndash108 2009

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[13] C M Croce ldquoCauses and consequences of microRNA dysreg-ulation in cancerrdquo Nature Reviews Genetics vol 10 no 10 pp704ndash714 2009

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[42] JW Nam OS Rissland D Koppstein and et al ldquoGlobalanalyses of the effect of different cellular contexts onmicroRNAtargetingrdquoMolecular Cell vol 53 pp 1031ndash1043 2014

[43] E Huntzinger and E Izaurralde ldquoGene silencing by microR-NAs contributions of translational repression and mRNAdecayrdquo Nature Reviews Genetics vol 12 no 2 pp 99ndash110 2011

[44] A Stroynowska-Czerwinska A Fiszer and W J KrzyzosiakldquoThe panorama of miRNA-mediated mechanisms in mam-malian cellsrdquo Cellular and Molecular Life Sciences vol 71 pp2253ndash2270 2014

[45] A Saumet G Vetter M Bouttier et al ldquoEstrogen and retinoicacid antagonistically regulate several microRNA genes to con-trol aerobic glycolysis in breast cancer cellsrdquo Molecular BioSys-tems vol 8 no 12 pp 3242ndash3253 2012

[46] K K Waltering K P Porkka S E Jalava et al ldquoAndrogenregulation of micro-RNAs in prostate cancerrdquoThe Prostate vol71 no 6 pp 604ndash614 2011

[47] W W Wang N Chatterjee S V Chittur J Welsh and MP Tenniswood ldquoEffects of 112057225 dihydroxyvitamin D3 andtestosterone onmiRNA andmRNA expression in LNCaP cellsrdquoMolecular Cancer vol 10 article 58 2011

[48] R Kulshreshtha M Ferracin S E Wojcik et al ldquoA microRNAsignature of hypoxiardquoMolecular andCellular Biology vol 27 no5 pp 1859ndash1867 2007

[49] Y Mao R Mohan S Zhang and X Tang ldquoMicroRNAs aspharmacological targets in diabetesrdquo Pharmacological Researchvol 73 pp 37ndash47 2013

[50] C Chen L Li H F Lodish and D P Bartel ldquoMicroRNAsmodulate hematopoietic lineage differentiationrdquo Science vol303 no 5654 pp 83ndash86 2004

[51] C P Morgan and T L Bale ldquoSex differences in microRNAregulation of gene expression no smoke just miRsrdquo Biology ofSex Differences vol 3 no 1 article 22 2012

[52] S Sharma and M Eghbali ldquoInfluence of sex differences onmicroRNA gene regulation in diseaserdquo Biology of Sex Differ-ences vol 5 no 1 article 3 2014

[53] N N Hooten K Abdelmohsen M Gorospe N Ejiogu A BZonderman and M K Evans ldquomicroRNA expression patternsreveal differential expression of target genes with agerdquo PLoSONE vol 5 no 5 Article ID e10724 2010

[54] N Noren Hooten M Fitzpatrick W H Wood III et al ldquoAge-related changes in microRNA levels in serumrdquo Aging (AlbanyNY) vol 5 pp 725ndash740 2013

[55] C Y Lai Y T Wu S L Yu et al ldquoModulated expression ofhuman peripheral blood microRNAs from infancy to adult-hood and its role in agingrdquoAging Cell vol 13 no 4 pp 679ndash6892014

[56] N Pencheva and S F Tavazoie ldquoControl of metastatic progres-sion by microRNA regulatory networksrdquo Nature Cell Biologyvol 15 no 6 pp 546ndash554 2013

[57] Y Li A Ahmad D Kong B Bao and F H Sarkar ldquoTargetingmicroRNAs for personalized cancer therapyrdquoMedical Principlesand Practice vol 22 pp 415ndash417 2013

[58] C Liu K Kelnar B Liu et al ldquoThemicroRNAmiR-34a inhibitsprostate cancer stem cells and metastasis by directly repressingCD44rdquo Nature Medicine vol 17 no 2 pp 211ndash215 2011

[59] Q Huang K Gumireddy M Schrier et al ldquoThe microRNAsmiR-373 and miR-520c promote tumour invasion and metasta-sisrdquo Nature Cell Biology vol 10 no 2 pp 202ndash210 2008

[60] Y Li CQiu J Tu et al ldquoHMDDv20 a database for experimen-tally supported human microRNA and disease associationsrdquoNucleic Acids Research vol 42 pp D1070ndashD1074 2013

[61] D Wang J Gu T Wang and Z Ding ldquoOncomiRDB adatabase for the experimentally verified oncogenic and tumor-suppressive microRNAsrdquo Bioinformatics 2014

[62] L He J M Thomson M T Hemann et al ldquoA microRNApolycistron as a potential human oncogenerdquo Nature vol 435no 7043 pp 828ndash833 2005

[63] T C Chang E A Wentzel O A Kent et al ldquoTransactivationof miR-34a by p53 broadly influences gene expression andpromotes apoptosisrdquoMolecular Cell vol 26 no 5 pp 745ndash7522007

[64] D G Johnson ldquoThe paradox of E2F1 oncogene and tumorsuppressor generdquoMolecular Carcinogenesis vol 27 pp 151ndash1572000

[65] B D Rowland R Bernards and D S Peeper ldquoThe KLF4tumour suppressor is a transcriptional repressor of p53 that actsas a context-dependent oncogenerdquo Nature Cell Biology vol 7no 11 pp 1074ndash1082 2005

[66] J Liang and G B Mills ldquoAMPK a contextual oncogene ortumor suppressorrdquo Cancer Research vol 73 no 10 pp 2929ndash2935 2013

[67] A Toker and Y R Chin ldquoAkt-ing up on SRPK1 oncogene ortumor suppressorrdquoMolecular Cell vol 54 pp 329ndash330 2014

[68] C Lobry P Oh M R Mansour A T Look and I AifantisldquoNotch signaling switching an oncogene to a tumor suppres-sorrdquo Blood vol 123 pp 2451ndash2459 2014


[69] N Felli L Fontana E Pelosi et al ldquoMicroRNAs 221 and 222inhibit normal erythropoiesis and erythroleukemic cell growthvia kit receptor down-modulationrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 102 no50 pp 18081ndash18086 2005

[70] P Pineau S Volinia K McJunkin et al ldquomiR-221 overex-pression contributes to liver tumorigenesisrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 107 no 1 pp 264ndash269 2010

[71] M Fabbri A Bottoni M Shimizu et al ldquoAssociation ofa microRNATP53 feedback circuitry with pathogenesis andoutcome of b-cell chronic lymphocytic leukemiardquo The Journalof the American Medical Association vol 305 no 1 pp 59ndash672011

[72] M V Iorio and C M Croce ldquoCauses and consequences ofMicroRNA dysregulationrdquo Cancer Journal vol 18 no 3 pp215ndash222 2012

[73] P Lopez-Serra and M Esteller ldquoDNA methylation-associatedsilencing of tumor-suppressor microRNAs in cancerrdquo Onco-gene vol 31 no 13 pp 1609ndash1622 2012

[74] G A Calin C Sevignani C D Dumitru et al ldquoHumanmicroRNA genes are frequently located at fragile sites andgenomic regions involved in cancersrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 101 no 9 pp 2999ndash3004 2004

[75] L Zhang J Huang N Yang et al ldquomicroRNAs exhibit highfrequency genomic alterations in human cancerrdquo Proceedings ofthe National Academy of Sciences of the United States of Americavol 103 no 24 pp 9136ndash9141 2006

[76] H Tagawa and M Seto ldquoA microRNA cluster as a target ofgenomic amplification inmalignant lymphomardquo Leukemia vol19 no 11 pp 2013ndash2016 2005

[77] VDavalos andM Esteller ldquoMicroRNAs and cancer epigeneticsa macrorevolutionrdquo Current Opinion in Oncology vol 22 no 1pp 35ndash45 2010

[78] Z Wang H Yao S Lin et al ldquoTranscriptional and epigeneticregulation of humanmicroRNAsrdquoCancer Letters vol 331 no 1pp 1ndash10 2013

[79] A Saumet G Vetter M Bouttier et al ldquoTranscriptional repres-sion of microRNA genes by PML-RARA increases expressionof key cancer proteins in acute promyelocytic leukemiardquo Bloodvol 113 no 2 pp 412ndash421 2009

[80] S Hua R Kittler and K P White ldquoGenomic antagonismbetween retinoic acid and estrogen signaling in breast cancerrdquoCell vol 137 no 7 pp 1259ndash1271 2009

[81] S R Viswanathan G Q Daley and R I Gregory ldquoSelectiveblockade of microRNA processing by Lin28rdquo Science vol 320no 5872 pp 97ndash100 2008

[82] C Blenkiron L D Goldstein N P Thorne et al ldquoMicroRNAexpression profiling of human breast cancer identifies newmarkers of tumor subtyperdquoGenome Biology vol 8 article R2142007

[83] K A Avery-Kiejda S G Braye J F Forbes and R J ScottldquoThe expression ofDicer andDrosha inmatchednormal tissuestumours and lymph node metastases in triple negative breastcancerrdquo BMC Cancer vol 14 article 253 2014

[84] G Di Leva and C M Croce ldquoMiRNA profiling of cancerrdquoCurrent Opinion in Genetics and Development vol 23 no 1 pp3ndash11 2013

[85] A J Lowery N Miller A Devaney et al ldquoMicroRNA sig-natures predict oestrogen receptor progesterone receptor and

HER2neu receptor status in breast cancerrdquo Breast CancerResearch vol 11 no 3 article R27 2009

[86] P J Mishra D Banerjee and J R Bertino ldquoMiRSNPs or MiR-polymorphisms new players inmicroRNAmediated regulationof the cell introducing microRNA pharmacogenomicsrdquo CellCycle vol 7 no 7 pp 853ndash858 2008

[87] D Landi F Gemignani R Barale and S Landi ldquoA catalog ofpolymorphisms falling in microRNA-binding regions of cancergenesrdquo DNA and Cell Biology vol 27 no 1 pp 35ndash43 2008

[88] R Duan C Pak and P Jin ldquoSingle nucleotide polymorphismassociated with mature miR-125a alters the processing of pri-miRNArdquoHumanMolecular Genetics vol 16 no 9 pp 1124ndash11312007

[89] Z Hu J Chen T Tian et al ldquoGenetic variants of miRNAsequences and non-small cell lung cancer survivalrdquo Journal ofClinical Investigation vol 118 no 7 pp 2600ndash2608 2008

[90] ZHu J Liang ZWang et al ldquoCommon genetic variants in pre-microRNAswere associated with increased risk of breast cancerin Chinese womenrdquoHuman Mutation vol 30 no 1 pp 79ndash842009

[91] B P Lewis C B Burge and D P Bartel ldquoConserved seedpairing often flanked by adenosines indicates that thousandsof human genes are microRNA targetsrdquo Cell vol 120 no 1 pp15ndash20 2005

[92] A E Bruno L Li J L Kalabus Y Pan A Yu and ZHu ldquomiRdSNP A database of disease-associated SNPs andmicroRNA target sites on 3rsquoUTRs of human genesrdquo BMCGenomics vol 13 no 1 article 44 2012

[93] A Bhattacharya J D Ziebarth and Y Cui ldquoSomamiR adatabase for somatic mutations impacting microRNA functionin cancerrdquo Nucleic Acids Research vol 41 no D1 pp D977ndashD982 2012

[94] M P Hamilton K Rajapakshe S M Hartig et al ldquoIden-tification of a pan-cancer oncogenic microRNA superfamilyanchored by a central core seedmotifrdquoNature Communicationsvol 4 article 2730 2013

[95] R Sabarinathan A Wenzel P Novotny et al ldquoTranscriptome-wide analysis of UTRs in non-small cell lung cancer revealscancer-related genes with SNV-induced changes on RNA sec-ondary structure and miRNA target sitesrdquo PLoS ONE vol 9Article ID e82699 2014

[96] C Chen D A Ridzon A J Broomer et al ldquoReal-timequantification of microRNAs by stem-loop RT-PCRrdquo NucleicAcids Research vol 33 no 20 article e179 2005

[97] M R Friedlander E Lizano A J Houben et al ldquoEvidence forthe biogenesis of more than 1000 novel human microRNAsrdquoGenome Biology vol 15 article R57 2014

[98] A Kozomara and S Griffiths-Jones ldquoMiRBase integratingmicroRNA annotation and deep-sequencing datardquo NucleicAcids Research vol 39 no 1 pp D152ndashD157 2011

[99] W Zhou M Y Fong Y Min G Somlo and L Liu ldquoCancer-secreted miR-105 destroys vascular endothelial barriers topromote metastasisrdquo Cancer Cell vol 25 pp 501ndash515 2014

[100] R M Drayton E Dudziec S Peter S Bertz and A Hart-mann ldquoReduced expression of miRNA-27a modulates cisplatinresistance in bladder cancer by targeting the cystineglutamateexchanger SLC7A11rdquoClinical Cancer Research vol 20 pp 1990ndash2000 2014

[101] H Wu Z Xiao H Zhang K Wang W Liu and Q Hao ldquoMiR-489 modulates cisplatin resistance in human ovarian cancercells by targeting Akt3rdquoAnticancer Drugs vol 25 no 7 pp 799ndash809 2014


[102] M Yang X Shan X Zhou T Qiu and W Zhu ldquomiR-1271regulates cisplatin resistance of human gastric cancer cell linesby targeting IGF1R IRS1 mTOR and BCL2rdquo Anti-CancerAgents in Medicinal Chemistry vol 14 no 6 pp 884ndash891 2014

[103] M Fabbri A Paone F Calore et al ldquoMicroRNAs bind to Toll-like receptors to induce prometastatic inflammatory responserdquoProceedings of the National Academy of Sciences of the UnitedStates of America vol 109 no 31 pp E2110ndashE2116 2012

[104] J R Chevillet I Lee H A Briggs Y He and K Wang ldquoIssuesand prospects of microRNA-based biomarkers in blood andother body fluidsrdquoMolecules vol 19 pp 6080ndash6105 2014

[105] J D Arroyo J R Chevillet E M Kroh et al ldquoArgonaute2complexes carry a population of circulating microRNAs inde-pendent of vesicles in human plasmardquo Proceedings of theNational Academy of Sciences of the United States of Americavol 108 no 12 pp 5003ndash5008 2011

[106] H Valadi K Ekstrom A Bossios M Sjostrand J J Leeand J O Lotvall ldquoExosome-mediated transfer of mRNAs andmicroRNAs is a novel mechanism of genetic exchange betweencellsrdquo Nature Cell Biology vol 9 no 6 pp 654ndash659 2007

[107] K C Vickers B T Palmisano B M Shoucri R D Shamburekand A T Remaley ldquoMicroRNAs are transported in plasma anddelivered to recipient cells by high-density lipoproteinsrdquoNatureCell Biology vol 13 no 4 pp 423ndash435 2011

[108] A Ruepp A Kowarsch and F Theis ldquoPhenomiR microRNAsin human diseases and biological processesrdquoMethodsMolecularBiology vol 822 pp 249ndash260 2011

[109] C P Goswami and H Nakshatri ldquoPROGmiR a tool foridentifying prognostic miRNA biomarkers in multiple cancersusing publicly available datardquo Journal of Clinical Bioinformaticsvol 2 no 1 article 23 2013

[110] A Lagana S Forte A Giudice et almiRo AmiRNAKnowledgeBase Database Oxford UK 2009

[111] F Russo S Di Bella G Nigita et al ldquomiRandola extracellularcirculating microRNAs databaserdquo PLoS ONE vol 7 no 10Article ID e47786 2012

[112] J Jarry D Schadendorf C Greenwood A Spatz and L C vanKempen ldquoThe validity of circulating microRNAs in oncologyfive years of challenges and contradictionsrdquo Molecular Oncol-ogy vol 8 no 4 pp 819ndash829 2014

[113] R S Leidner L Li and C L Thompson ldquoDampening enthusi-asm for circulatingmicroRNA in breast cancerrdquo PLoS ONE vol8 no 3 Article ID e57841 2013

[114] N Becker and C M Lockwood ldquoPre-analytical variables inmiRNA analysisrdquo Clinical Biochemistry vol 46 no 10-11 pp861ndash868 2013

[115] K W Witwer ldquoData submission and quality in microarray-based MicroRNA profilingrdquo Clinical Chemistry vol 59 no 2pp 392ndash400 2013

[116] C C Pritchard H H Cheng and M Tewari ldquoMicroRNA pro-filing approaches and considerationsrdquoNature Reviews Geneticsvol 13 no 5 pp 358ndash369 2012

[117] K Wang Y Yuan J Cho S McClarty D Baxter and D JGalas ldquoComparing the MicroRNA spectrum between serumand plasmardquo PLoS ONE vol 7 no 7 Article ID e41561 2012

[118] H H Cheng H S Yi Y Kim et al ldquoPlasma processing condi-tions substantially influence circulating microRNA biomarkerlevelsrdquo PLoS ONE vol 8 no 6 Article ID e64795 2013

[119] T Blondal S J Nielsen A Baker et al ldquoAssessing sample andmiRNA profile quality in serum and plasma or other biofluidsrdquoMethods vol 59 no 1 pp S1ndashS6 2013

[120] M B Kirschner S C Kao J J Edelman et al ldquoHaemolysisduring sample preparation altersmicroRNA content of plasmardquoPLoS ONE vol 6 no 9 Article ID e24145 2011

[121] C C Pritchard E Kroh B Wood et al ldquoBlood cell origin ofcirculating microRNAs a cautionary note for cancer biomarkerstudiesrdquo Cancer Prevention Research vol 5 no 3 pp 492ndash4972012

[122] M B Kirschner J J Edelman S C Kao et al ldquoThe impactof hemolysis on cell-free microRNA biomarkersrdquo Frontiers inGenetics vol 4 article 94 2013

[123] G Tzimagiorgis E Z Michailidou A Kritis A K Markopou-los and S Kouidou ldquoRecovering circulating extracellular orcell-free RNA from bodily fluidsrdquo Cancer Epidemiology vol 35no 6 pp 580ndash589 2011

[124] E M Kroh R K Parkin P S Mitchell and M TewarildquoAnalysis of circulating microRNA biomarkers in plasma andserum using quantitative reverse transcription-PCR (qRT-PCR)rdquoMethods vol 50 no 4 pp 298ndash301 2010

[125] Y Kim J Yeo B Kim M Ha and V N Kim ldquoShort structuredRNAswith lowGC content are selectively lost during extractionfrom a small number of cellsrdquoMolecular Cell vol 46 no 6 pp893ndash895 2012

[126] M Monleau S Bonnel T Gostan et al ldquoComparison ofdifferent extraction techniques to profile microRNAs fromhuman sera and peripheral blood mononuclear cellsrdquo BMCGenomics vol 15 article 395 2014

[127] G S Mack ldquoMicroRNA gets down to businessrdquoNature Biotech-nology vol 25 no 6 pp 631ndash638 2007

[128] G Manceau S Imbeaud R Thiebaut F Liebaert and KFontaine ldquoHsa-miR-31-3p expression is linked to progression-free survival in patients with KRAS wild-type metastatic col-orectal cancer treated with anti-EGFR therapyrdquo Clinical CancerResearch 2014

[129] A G Seto ldquoThe road toward microRNA therapeuticsrdquo TheInternational Journal of Biochemistry amp Cell Biology vol 42 no8 pp 1298ndash1305 2010

[130] R Garzon G Marcucci and C M Croce ldquoTargeting microR-NAs in cancer rationale strategies and challengesrdquo NatureReviews Drug Discovery vol 9 no 10 pp 775ndash789 2010

[131] J A Broderick and P D Zamore ldquoMicroRNA therapeuticsrdquoGene Therapy vol 18 no 12 pp 1104ndash1110 2011

[132] DNalls SN TangMRodova R K Srivastava and S ShankarldquoTargeting epigenetic regulation of mir-34a for treatment ofpancreatic cancer by inhibition of pancreatic cancer stem cellsrdquoPLoS ONE vol 6 no 8 Article ID e24099 2011

[133] Y Saito and P A Jones ldquoEpigenetic activation of tumorsuppressor microRNAs in human cancer cellsrdquo Cell Cycle vol5 no 19 pp 2220ndash2222 2006

[134] J-J Zhao J Lin H Yang et al ldquoMicroRNA-221222 negativelyregulates estrogen receptor 120572 and is associated with tamoxifenresistance in breast cancerrdquoThe Journal of Biological Chemistryvol 283 no 45 pp 31079ndash31086 2008

[135] C Rolfo D Fanale D S Hong et al ldquoImpact of microRNAs inresistance to chemotherapy and novel targeted agents in non-small cell lung cancerrdquo Current Pharmaceutical Biotechnology2014

[136] D R Cochrane N S Spoelstra E N Howe S K Nordeenand J K Richer ldquoMicroRNA-200c mitigates invasiveness andrestores sensitivity to microtubule-targeting chemotherapeuticagentsrdquo Molecular Cancer Therapeutics vol 8 no 5 pp 1055ndash1066 2009


[137] K A Lennox and M A Behlke ldquoChemical modification anddesign of anti-miRNA oligonucleotidesrdquo Gene Therapy vol 18no 12 pp 1111ndash1120 2011

[138] J Stenvang A N Silahtaroglu M Lindow J Elmen and SKauppinen ldquoThe utility of LNA in microRNA-based cancerdiagnostics and therapeuticsrdquo Seminars in Cancer Biology vol18 no 2 pp 89ndash102 2008

[139] SObadCO dos Santos A Petri et al ldquoSilencing ofmicroRNAfamilies by seed-targeting tiny LNAsrdquo Nature Genetics vol 43no 4 pp 371ndash378 2011

[140] J Krutzfeldt N Rajewsky R Braich et al ldquoSilencing ofmicroRNAs in vivo with ldquoantagomirsrdquordquo Nature vol 438 no7068 pp 685ndash689 2005

[141] J Elmen M Lindow S Schutz et al ldquoLNA-mediatedmicroRNA silencing in non-human primatesrdquo Nature vol 452no 7189 pp 896ndash899 2008

[142] M Lindow and S Kauppinen ldquoDiscovering the first microrna-targeted drugrdquo Journal of Cell Biology vol 199 no 3 pp 407ndash412 2012

[143] M S Ebert and P A Sharp ldquoMicroRNA sponges progress andpossibilitiesrdquo RNA vol 16 no 11 pp 2043ndash2050 2010

[144] M S Ebert J R Neilson and P A Sharp ldquoMicroRNA spongescompetitive inhibitors of small RNAs in mammalian cellsrdquoNature Methods vol 4 no 9 pp 721ndash726 2007

[145] J Kluiver J H Gibcus C Hettinga et al ldquoRapid generation ofmicroRNA sponges for microRNA inhibitionrdquo PLoS ONE vol7 no 1 Article ID e29275 2012

[146] Y Tay J Rinn and P P Pandolfi ldquoThe multilayered complexityof ceRNA crosstalk and competitionrdquoNature vol 505 pp 344ndash352 2014

[147] R Denzler V Agarwal J Stefano D P Bartel and M StoffelldquoAssessing the ceRNA hypothesis with quantitative measure-ments of miRNA and target abundancerdquoMolecular Cell vol 54no 5 pp 766ndash776 2014

[148] D Cazalla T Yario and J A Steitz ldquoDown-regulation of a hostMicroRNA by a Herpesvirus saimiri noncoding RNArdquo Sciencevol 328 no 5985 pp 1563ndash1566 2010

[149] D D Vo C Staedel L Zehnacker et al ldquoTargeting the produc-tion of oncogenic microRNAs with multimodal synthetic smallmoleculesrdquo ACS Chemical Biology vol 9 pp 711ndash721 2013

[150] J C Henry A C P Azevedo-Pouly and T D SchmittgenldquoMicroRNA replacement therapy for cancerrdquo PharmaceuticalResearch vol 28 no 12 pp 3030ndash3042 2011

[151] V J Craig A TzankovM Flori C A Schmid A G BaDer andAMuller ldquoSystemic microRNA-34a delivery induces apoptosisand abrogates growth of diffuse large B-cell lymphoma in vivordquoLeukemia vol 26 no 11 pp 2421ndash2424 2012

[152] M Agostini and R A Knight ldquomiR-34 from bench to bedsiderdquoOncotarget vol 5 pp 872ndash881 2014

[153] A G Bader ldquoMiR-34mdasha microRNA replacement therapy isheaded to the clinicrdquo Frontiers in Genetics vol 3 article 1202012

[154] Q L Hu Q Y Jiang X Jin et al ldquoCationic microRNA-delivering nanovectors with bifunctional peptides for efficienttreatment of PANC-1 xenograft modelrdquo Biomaterials vol 34no 9 pp 2265ndash2276 2013

[155] J D Palmer B P Soule B A Simone N G Zaorsky L Jin andN L Simone ldquoMicroRNA expression altered by diet can foodbe medicinalrdquo Ageing Research Reviews 2014

[156] L Garcıa-Segura M Perez-Andrade J Miranda-Rıos and CPiso ldquoThe emerging role of MicroRNAs in the regulation of

gene expression by nutrientsrdquo Journal of Nutrigenetics andNutrigenomics vol 6 no 1 pp 16ndash31 2013

[157] C C Dahm RH Keogh E A Spencer et al ldquoDietary fiber andcolorectal cancer risk a nested case-control study using fooddiariesrdquo Journal of the National Cancer Institute vol 102 no 9pp 614ndash626 2010

[158] S Hu T S Dong S R Dalal et al ldquoThe microbe-derived shortchain fatty acid butyrate targets miRNA-dependent p21 geneexpression in human colon Cancerrdquo PLoS ONE vol 6 no 1Article ID e16221 2011

[159] T R Cech and J A Steitz ldquoThe noncoding RNA revolution-trashing old rules to forge new onesrdquo Cell vol 157 pp 77ndash942014

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of


Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology


Molecular Biology International

GenomicsInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


BioinformaticsAdvances in

Marine BiologyJournal of



Signal TransductionJournal of


BioMed Research International

Evolutionary BiologyInternational Journal of



Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Genetics Research International


Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational



Enzyme Research



Microbiology


will save time and improve cost effectiveness not to mentionsignificantly improving patientsrsquo quality of life by limiting theadverse effects of inappropriate treatments [2 3]

One prerequisite for the development of personalizedmedicine is the identification of combinations of biomarkersto guide a physicianrsquos clinical decision It is in this context thatthe potential of microRNAs (miRNAs) a particular class ofsmall noncoding RNAs has rapidly become apparent [4ndash6]To date more than two thousand human miRNAs have beenidentified [7] These small RNAs orchestrate the expressionof the genome at the posttranscriptional level and adapt theprotein output to various intracellular or extracellular stimuliAs such they impact many if not all cellular processes andtheir deregulation is causative of many human malignanciesincluding cancers [8ndash11] A plethora of researchers havenow implicated miRNAs in the initiation and progression ofprimary tumors as well as in metastasis formation [12ndash14]More than 12600 publications related to miRNA and cancerare listed in the NCBI PubMed database and their numberexponentially grows Advantageously cancer cell types tendto have a highly specific cellular repertoire of miRNAs [15ndash18] The expression levels of miRNA can be monitored ina variety of human specimens including fresh or formalin-fixed paraffin embedded (FFPE) tissues [19 20] as well asin almost all human body fluids [21ndash25] Moreover recentstudies revealed that specific miRNA expression levels inbiological fluids are associated with chemotherapy responses[23 26 27] Hence in addition to their potential as targets ofnovel anticancer therapies several aspects of miRNA biologymake them excellent candidates as biomarkers to be used ininnovative and noninvasive tests aimed at identifying variouscancers (diagnosis) predicting their outcome (prognosis)and monitoring their treatments (theranosis) [21 25 28ndash31]Here we review the different aspects of miRNA biology thatestablish their potential in the emerging field of personalizedmedicine against cancers We also present several knownlimitations of their exploitation as well as future challengesand ongoing industrial developments

2 miRNA Biogenesis andMechanism of Action

miRNAs are noncoding RNAs typically sim18ndash22 nucleotideslong which are generated through a complex multistepprocess Several excellent reviews have already thoroughlydescribed this process (see [32ndash35]) We focus here on theevents required for the understanding of this review MiRNAgenes are first transcribed by RNA polymerase II into longcapped and polyadenylated primarymiRNAprecursors (pri-miRNAs) The pri-miRNAs are subsequently processed bythe nuclear RNase III enzymeDrosha into precursormiRNAs(pre-miRNAs) [36ndash38] The pre-miRNAs are exported fromthe nucleus to the cytoplasm where they are cleaved by thecytoplasmic RNase III enzyme Dicer into a double-strandedRNA duplex (miR-5pmiR-3p) Alternative pathways existthat bypass either the Drosha or the Dicer steps [39] butthese pathways invariably produce a miR-5pmiR-3p duplexThe two strands of the duplex are then incorporated into the

effector complex called the miRNP complex which containsseveral proteins including the key Argonaute proteins Onestrand of the miRNA duplex then redirects the miRNP ontoRNAs that harbor partial sequence complementarity Thestudy of the mechanisms responsible for the recognitionof RNAs by miRNAs is an intense field of research withrapidly evolving concepts (eg location of miRNA bindingsites [40 41]) Canonical models are based on imperfectbase-pairing between the mature miRNA and the targetedRNA The extent to which the 51015840 end of the mature miRNA(referred to as the ldquoseedrdquo) pairs with the targeted RNA isof particular importance for the efficacy of miRNA-targetinteractions [42] The miRNP complex eventually inducesmRNA degradation andor repression of translation [43 44]While the formerrsquos mechanism relies on deadenylation andfurther exonucleolytic cleavage of the mRNA the latterrsquosremains unclear and is debated as translation repressioncould occur at different steps inhibition of initiation inhi-bition of elongation cotranslational protein degradation orpremature termination of translation [43]

The expression of miRNAs is a tightly regulated processthat is extremely sensitive to intra- and extracellular stimuli(eg hormones vitamins pharmacological molecules orhypoxia) [13 45ndash49] As a consequence each cell type at aparticular time and a particular location harbors a particularmiRNA repertoire This important concept constitutes thebasis of the remarkable interest in miRNAs within the field ofoncology The potential importance of miRNAs to medicinewas first highlighted by the seminal findings of Chen et al[50] who demonstrated that some miRNAs are expressedin hematopoietic cells and showed that their expressionwas dynamically regulated during early hematopoiesis andlineage commitment Importantly they showed that miR-181 was preferentially expressed in the B-lymphoid cells andthat its ectopic expression in hematopoietic stemprogenitorcells led to an increased fraction of B-lineage cells Thus itwas illustrated that it is possible to distinguish different celltypes or different cellular conditions (ie treatment) basedon miRNA profiling Moreover miRNA expression levels insomatic cells of male and female patients can differ likelydue to exposure to specific hormones (eg testosteroneestrogen and androgen) an observation that can explaingender-related differences noted in disease outcome andpathogenesis [51 52] Similarly the expression of somemiRNAs can be linked to aging [53ndash55]The specificity of thecellular miRNA repertoire and its sensitivity to a large panelof intraextracellular stimuli and characteristics (includinggender and age) have stimulated interest not only in basicresearch focused on deciphering the contribution of miRNAsto cancer development but also in more applied researchaimed at evaluatingmiRNAsrsquo potential in cancer personalizedmedicine

3 miRNAs and Cancer

Extensive research has shown that miRNAs play essentialroles in cancer initiation progression and metastasis forma-tion [56ndash59] The miRNA expression levels in tumors canbe up- or downregulated compared to normal tissue and























7 Conclusion






Acknowledgments


References













































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology























7 Conclusion






Acknowledgments


References













































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology





Acknowledgments


References













































































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology














































































































































Volume 2014

Zoology






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology

Review Article The Potential of MicroRNAs in Personalized...

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Transcript of Review Article The Potential of MicroRNAs in Personalized...