review article micrornas in hepatocellular...

Review ArticleMicroRNAs in Hepatocellular CarcinomaCarcinogenesis Progression and Therapeutic Target

Chao-Hung Hung Yi-Chun Chiu Chien-Hung Chen and Tsung-Hui Hu

Division of Hepatogastroenterology Department of Internal Medicine Chang Gung Memorial Hospital-KaohsiungMedical Center Chang Gung University College of Medicine 123 Ta Pei Road Niao Sung Kaohsiung 833 Taiwan

Correspondence should be addressed to Chao-Hung Hung chh4366yahoocomtw

Received 7 December 2013 Revised 16 February 2014 Accepted 12 March 2014 Published 2 April 2014

Academic Editor Wei Mike Liu

Copyright copy 2014 Chao-Hung Hung et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Hepatocellular carcinoma (HCC) is the third leading cause of death from cancer with dismal outcomes and an increasing incidenceworldwide Hepatocarcinogenesis is a multistep process that progresses from chronic hepatitis through cirrhosis andor dysplasticnodule toHCCHowever the detailedmolecular pathogenesis remains unclearMicroRNAs (miRNAs) small noncodingRNAs thatregulate the translation ofmany genes have emerged as key factors involved in several biological processes including developmentdifferentiation and cell proliferation Recent studies have uncovered the contribution of miRNAs to the cancer pathogenesis asthey can behave as oncogenes or tumor suppressor genes In addition other studies have demonstrated their potential values inthe clinical management of HCC patients as some miRNAs may be used as prognostic or diagnostic markers In this review wesummarize current knowledge about the roles of miRNAs in carcinogenesis and progression of HCCWe also discuss the potentialapplication of miRNAs as diagnostic biomarkers and their potential roles in the intervention of HCC

1 Introduction

Hepatocellular carcinoma (HCC) is the sixth most commonmalignancy and the third-leading cause of cancer-relateddeath in theworld [1]The incidence rates ofHCCare increas-ing in many parts of the world including the United Statesand central Europe The overall 5-year survival rate is 5ndash9from the time of clinical diagnosis of HCC and the dismalprognosis is largely caused by late detection of the tumors[2 3] Although the 5-year survival is better for patients whoundergo curative resection if the tumor is detected earlythese patients still have a high rate of recurrence [4 5]Etiologically hepatocarcinogenesis is closely associated withchronic hepatitis B virus (HBV) and hepatitis C virus (HCV)infections [6ndash8] More than 90 of HCC cases develop inchronically inflamed liver as a result of viral hepatitis andalcohol abuse and in increasing incidence in patients withnonalcoholic fatty liver disease [9] However the underlyingmolecular pathogenesis is not completely understood

HCC is pathologically and clinically heterogeneous Theprognosis depends on the aggressiveness of the HCC and

residual liver function [10] The progression of HCC isthought to involve the deregulation of genes that are criticalto cellular processes such as cell cycle control cell growthapoptosis and cell migration and spreading In the pastdecades studies have focused on investigating the genesand proteins underlying the development of HCC [11 12]Recently an increasing number of reports have described anew class of small regulatory RNAmolecules termedmicroR-NAs (miRNAs) that are implicated in HCC development andprogression

miRNAs are a class of small noncoding RNAs thatnegatively regulate gene expression by interacting with the31015840 untranslated region (UTR) of protein-coding mRNABy recruiting the RNA-induced silencing factor complexmiRNAs binding generally leads to translational suppressionandor degradation of the target transcript [13ndash16] MiRNAshave emerged as key factors involved in several biologicalprocesses including development differentiation cell prolif-eration and tumorigenesis [17] The involvement of miRNAsin cancer pathogenesis has been well established as they canbehave as oncogenes or tumor suppressor genes depending

Hindawi Publishing CorporationBioMed Research InternationalVolume 2014 Article ID 486407 11 pageshttpdxdoiorg1011552014486407

2 BioMed Research International

on the cellular function of their targets [18] Dysregulationof miRNAs in cancer has been repeatedly described forexample in prostate bladder and kidney cancer [19] breastcancer [20] and colon cancer [21]

This review will elaborate on the aberrant expressionof miRNAs in HCC and the pathological implications andmolecular functions of some well-characterized oncogenicand tumor suppressive miRNAs Furthermore we will dis-cuss the clinical prospect of miRNAs as diagnostic andprognostic biomarkers of HCC and their potential roles incancer treatment

2 miRNAs Generation and Function

21 miRNAs Biogenesis The generation of mature miRNAsis a multistep process that starts with the initial transcriptionof their genes by RNA polymerase II This results in longcapped and polyadenylated primary miRNAs of approxi-mately 1ndash4 kb [22] These transcripts are then cleaved by themicroprocessor complex which consists of the nuclease Dro-sha and the double-stranded RNA-binding protein DiGeorgesyndrome critical region gene 8 (DGCR8) into a precursormiRNA of 60ndash100 nucleotides The pre-miRNA is subse-quently transported from the nucleus to the cytoplasm byexportin 5 and further cleaved by the RNase enzyme Dicerinto double-stranded miRNAs [23] These two strands areseparated by helicases and the mature strand is incorporatedinto the RNA-induced silencing complex (RISC) The briefsummary of miRNA biogenesis is shown in Figure 1

Typically mature miRNAs regulate gene expressionthrough sequence-specific binding to the 31015840 UTR of a targetmRNA but recent evidence indicates that miRNAs can alsobind to other regions of a target mRNA [24 25]ThemiRNA-mRNA interaction usually causes translational repressionandor mRNA cleavage and thus reduces the final proteinoutput However this traditional understanding of miRNAsas negative regulators of gene expression has recently beenchallenged by the discovery of new and unexpected mech-anisms of action of miRNAs This includes evidence thatmiRNAs can also increase the translation of a target mRNAby recruiting protein complexes to the Adenylate-uridylate-(AU-) rich elements of the mRNA [26] or they can indirectlyincrease the target protein output by derepressing mRNAtranslation by interactingwith proteins that block the transla-tion of the target gene [27] Also there is evidence indicatingthat miRNAs can switch the regulation from repression toactivation of target gene translation in conditions of cell cyclearrest [26]

In addition to functioning within cells miRNAs areabundant in the bloodstream and can act at neighboring cellsand at more distant sites within the body in a hormone-like fashion suggesting that they can mediate both short-and long-range cell-cell communication [28 29] MiRNAstogether with RNA-binding proteins can be packaged andtransported extracellularly by exosomes or microvesicles [3031] Likewise miRNAs in the bloodstream can be taken upby the recipient cells via endocytosis and further bound tointracellular proteins such as toll-like receptors (TLR) [28]

Nucleus

Transcription

Processing

Exporting

Dicing

Incorporationinto RISC

miRNA gene

Pri-miRNA

Pre-miRNA

Pre-miRNA

miRNA duplex

Mature miRNA

RNA Pol II

Drosha-DGCR8

Exportin 5

Dicer

RISC

Cytoplasm

Figure 1 Brief summary in miRNA biogenesis (1) initial tran-scription by RNA polymerase (Pol II) into primary miRNA (pri-miRNA) (2) processing byDrosha-DGCR8 into a precursormiRNA(pre-miRNA) (3) export of the pre-miRNA via Exportin-5 from thenucleus to the cytoplasm (4) cleaved by theRNase enzymeDicer intodouble-stranded miRNAs (5) incorporation into the RNA-inducedsilencing complex (RISC)

22 miRNAs Regulation and Interaction Although miRNAstypically repress target gene expression recent work hasrevealed that regulation in the miRNA pathway is a two-way street Not only can base pairing between a miRNAand its target result in repressed target expression but theseinteractions can also have an impact on the levels of themiRNA [32] However the reciprocal effect of targets onmiRNAs remains entirely unclear In some cases targetinteractions offer a protective influence on miRNA stabilitywhereas in others the outcome is miRNA degradation [3334]

In addition to the binding between miRNA and 31015840UTR of its target mRNA recent studies have identified adirect interaction between two individual miRNAs throughsequence match [35 36] Chen et al provided functionalevidence of miRNA-miRNA interaction between miR-107and let-7 Using a mutation system they further identifiedthe essential role of an internal loop within the miR-107let-7 duplex which provided important clues for furtherinvestigation on the underlying mechanism [35] This newlydiscovered regulation sheds light on our current knowledgein the posttranscriptional control of miRNA Consideringthe interaction and the multifaceted roles of miRNA theregulation network of miRNA becomes more complex thanwe originally thought

3 miRNAs in Hepatocarcinogenesis

miRNAs fine-tune all physiological and many pathologicalprocesses that are fundamental to normal liver functionsand liver disease [37] Recently advanced progress has been

BioMed Research International 3

made in identifying miRNAs as important regulators of geneexpression and their association with or control of variousliver diseases such as viral hepatitis fibrosis and HCC [38ndash40]There is nowmounting experimental evidence indicatingthat miRNAs may act as oncogenes or tumor suppressorsby directly or indirectly controlling the expression of keyproteins involved in cancer-associated pathways [18]

31 Downregulation of Tumor-Suppressing miRNAs in HCCDownregulation of subsets of miRNAs is a common findingin HCC suggesting that some of these miRNAs may actas putative tumor suppressor genes Restoration of tumorsuppressive miRNAs leads to cell cycle block increasedapoptosis and reduced tumor angiogenesis andmetastasis byinhibiting migration and invasion Of these miRNAs miR-122 and miR-199 appear to be particularly important in HCC[61 62 81]

The liver-specific miR-122 is the most abundant miRNAin the liver and it plays an important role in regulatinghepatocyte development and differentiation [82 83] MiR-122 is downregulated in HCC tumor tissues and cancer celllines and overexpression of miR-122 has been found toinduce apoptosis and suppress proliferation in HepG2 andHep3B cells [41] The role of miR-122 in liver cancer hasbeen demonstrated directly by the generation of miR-122knockout mice [84 85] These mice were characterized byhepatic inflammation fibrosis and development of sponta-neous tumors similar to HCC demonstrating the tumor-suppressor function of this miRNA and its important rolein liver metabolism and differentiation of hepatocytes [8485] Previous studies have found that cyclin G1 is a directtarget of miR-122 [49] and that miR-122cyclin G1 interactionmodulates p53 activity and affects doxorubicin sensitivity inhuman HCC cells [86] In a mouse model the absence ofcyclin G1 is associated with less susceptibility to developingliver tumors [87]

All three members of the miR-199 family that is miR-199a-1 miR-199a-2 and miR-199b have emerged as beingfrequently downregulated in HCC [63 88] Phenotypicallyenforced expression of miR-199a in HCC cells leads tocell cycle arrest at G1 phase reduced invasive capabilityand enhanced susceptibility to hypoxia [63 88] In HCCpatients downregulation of miR-199a was associated with ahigher recurrence rate and shorter time to recurrence aftersurgery These effects could be explained by modulation oftarget genes such as MET mammalian target of rapamycin(mTOR) and hypoxia-inducible factors (HIF)-1120572 [63 8889] Another important target of miR-199 in HCC is CD44which is a transmembrane glycoprotein involved in cell-cellinteraction cell adhesion and migration [90]

The majority of downregulated tumor-suppressing miR-NAs in HCC and their involvements with cellular processesare listed in Table 1

32 Upregulation of Oncogenic miRNAs in HCC OncogenicmiRNAs that are upregulated in HCC potentially targetmany tumor suppressive genes Experimental suppressionof oncogenic miRNAs helps restoring expression of tumor

suppressive genes that initiates apoptosis and inhibits cellproliferation angiogenesis and metastasis in HCC Func-tional analysis of these oncogenic miRNAs and their targetedgenes in liver cancer will help in understanding the role ofmiRNAs in hepatocarcinogenesis as molecular biomarkersand possible targets for development of oncogenic miRNAs-targeted therapy of HCC Among the miRNAs that areupregulated in HCC there is evidence in support of thetumor-promoting activity of miR-221mir-222 and miR-21[91ndash94]

MiR-221 and miR-222 are two highly homologous miR-NAs and upregulated in several types of human tumorswhich act as oncogenes or tumor suppressors depending ontumor system [95] HCC cells overexpressing miR-221 showincreased growth proliferation migration and invasioncapability [96 97] There is a strong relationship betweenthe high expression of miR-222 and tumor progression andpatient survival Overexpression of miR-222 confers cellmigratory advantages in HCC through enhancing ProteinKinase B (AKT) signaling [78]

MiR-21 is the most commonly overexpressed miRNAin cancer and a proven oncogene [94] There are manymechanisms associated with elevated miR-21 levels Theencoding genetic locus 17q23 is amplified in many solidtumors [98 99] In addition miR-21 expression is stim-ulated by a variety of cancer-associated pathways such ashypoxia inflammation activator protein (AP)-1 and steroidhormones [100ndash102] MiR-21 is upregulated in HCC cellsand tissues which are associated with the capacity of cancercell migration and invasion in HCC where the miR-21expression is inversely correlated with the protein expressionof its targeted gene programmed cell death 4 (PDCD4) andsignaling molecules of its downstream pathway [103] MiR-21 can also regulate HCC cellular proliferation and tumorgrowth by inducing epithelial to mesenchymal transition(EMT) through AKTERK pathways [104]

More upregulated oncogenic miRNAs in HCC and theirinvolvements with cellular processes are listed in Table 2

33 Deregulated miRNAs in Cell Cycle and Apoptosis SeveralmiRNAs have been reported to be implicated in cell cycleregulationOf themmiR-26a andmiR-195 whichwere foundto be significantly downregulated in HCC might block theG(1)S transition by repressing retinoblastoma- (Rb-)E2Fsignaling through targeting multiple molecules includingcyclin D1 cyclin-dependent kinase (CDK)6 and E2F3 [4344] MiR-34a as a downstream target of tumor suppressorp53 can function as a link between p53 signaling and the cellcycle regulation by targeting cyclin D1 CDK4 and CDK2 inHCC [47]MiR-221 andmiR-222 have been reported to targetCDKN1Bp27Kip1 and CDKN1Cp57Kip2 while miR-223participates in regulating the G2M transition mediated bystathmin-1 [73] In addition miR-193b and miR-520b caninduce cell cycle arrest and inhibit the invasion andmigrationof HCC cells by the suppressing the ability of HCC cells toform colonies [105 106]

There are a number of deregulated miRNAs involvedin the regulation of apoptosis Besides cell cycle regulation


Table 1 Downregulated tumor-suppressing miRNAs in HCC

miRNA Target genes Characteristics ReferencesMiR-1 c-Met ET-1 Metastasis proliferation [41]MiR-7 PIK3CD mTOR p70S6K Tumorigenesis metastasis [42]MiR-26a CDK6 cyclin D1 Cell cycle [43 44]MiR-29 Bcl-2 Bcl-w Ras Apoptosis [45 46]MiR-34a cyclin D1 CDK4 and CDK2 c-Met Cell cycle proliferation apoptosis metastasis [47 48]MiR-122 cyclin G1 Bcl-w TACE Apoptosis angiogenesis metastasis [49ndash51]MiR-124 ROCK2 EZH2 Metastasis [52]MiR-125b Bcl-2 Bcl-w Apoptosis [53]MiR-126 VEGF VCAM-1 Angiogenesis metastasis [54ndash56]MiR-141 EMT Metastasis [57 58]MiR-146a TRAF6 IRAK1 Metastasis [59]MiR-195 CDK6 cyclin D1 Cell cycle apoptosis [43 44]MiR-198 c-Met Metastasis [60]MiR-199a mTOR PAK4 Cell growth apoptosis [61ndash63]MiR-200 EMT Metastasis [57 58]MiR-449 c-Met Metastasis [64]ET1 endothelin-1

Table 2 Upregulated oncogenic miRNAs in HCC

miRNA Target genes Characteristics ReferencesMiR-15a Bcl-2 cyclin D1 AKT3 Proliferation apoptosis [65]MiR-16-1 Bcl-2 cyclin D1 AKT3 Proliferation apoptosis [65]MiR-17 c-Myc E2F Angiogenesis [66 67]MiR-18 c-Myc E2F Angiogenesis [66 67]MiR-19 c-Myc E2F Angiogenesis [66 67]MiR-20a c-Myc E2F Angiogenesis [66 67]MiR-21 PTEN metastasis [68]MiR-25 Bim Apoptosis [69]MiR-92-1 c-Myc E2F Angiogenesis [66 67]MiR-93 Bim Apoptosis [69]MiR-106b Bim Apoptosis [69]MiR-148a PTEN Metastasis [70]MiR-155 RhoA TLR Metastasis [56 71]MiR-216a PTEN Metastasis [72]MiR-221 Bmf CDKN1Bp27Kip1 CDKN1Cp57Kip2 PTEN Apoptosis proliferation angiogenesis [73ndash77]MiR-222 AKT PTEN Metastasis angiogenesis [51 74 78]MiR-224 Bcl-2 Bcl-w Apoptosis [79]MiR-519d PTEN Metastasis [80]

miR-221 and miR-222 enhance the resistance to TNF-relatedapoptosis-inducing ligand- (TRAIL-) induced apoptosisby negatively regulating phosphatase and tensin homolog(PTEN) and metalloproteinase inhibitor 3 (TIMP3) [74]MiR-221 can also downregulate twomembers of proapoptoticB-cell lymphoma- (Bcl-) 2 family Bcl-2-modifying factor(Bmf) and p53 upregulated modulator of apoptosis (PUMA)[75 76] The expression of three members of miR106b-25 cluster (miR-25 miR-93 and miR-106b) is inverselycorrelated with Bim expression [69] On the contrary miR-125b [53] miR-224 [79] miR-29 [45] and miR-122 [107] cantarget the antiapoptotic members Bcl-2 inducing myeloid

leukemia cell differentiation protein (Mcl-1) and Bcl-2-likeprotein 2 (Bcl-w)

Many miRNAs have been shown to regulate the expres-sion of proteins in tyrosine kinase receptors (RTKs) whichinitiates a signaling cascade that eventually leads to cell pro-liferation and survival MiR-216a [79] miR-21 [68] miR-148a[70] miR-221222 [76] and miR-519d [80] can downregulatePTEN in HCC leading to the activation of phosphatidyli-nositide 3-kinases (PI3K)AKTmTOR pathway In additionmiR-7 regulates PI3KAKT pathway by targeting to PIK3CDmTOR and p70S6K [42] Restoring attenuated levels of miR-199a-3p inHCC cells led toG1-phase cell cycle arrest reduced


invasive capability enhanced susceptibility to hypoxia andincreased sensitivity to doxorubicin-induced apoptosis [63]c-Met can also be suppressed by other miRNAs includingmiR-1 [41] miR-198 [60] miR-449 [64] and miR-34a [48]

4 miRNAs in HCC Progression

41 miRNAs Function in Angiogenesis Angiogenesis andmetastasis play important roles in the progression and recur-rence of HCC MiRNAs are highly expressed in endothelialcells and recent data suggest that they regulate aspectsof vascular development and angiogenesis [108] SeveralmiRNAs have been identified that exert proangiogenic orantiangiogenic effects [54 108ndash110] MiR-221 and miR-222are known to modulate the angiogenic properties of humanumbilical vein endothelial cells [77 111]Throughdirectly reg-ulating downstream targets such as c-kit p27Kip1 p57Kip2and cyclin G1 miR-221 and miR-222 impact migration andproliferation of endothelial cells [111] In addition the miR-15a-16-1 cluster can promote apoptosis as well as inhibit cellproliferation and vascular endothelial growth factor (VEGF)expression by targeting Bcl-2 cyclin D1 wingless typeMousemammary tumor virus (MMTV) integration site fam-ily member 3A (WNT3A) AKT serinethreonine-protein-kinase (AKT3) ribosomalprotein-S6Mitogen-activated pro-tein (MAP)-kinases and NF-kappaB activator MAP3-KIP3[65] MiR-122 can inhibit angiogenesis and intrahepaticmetastasis by suppressing the expression of tumor necrosisfactor-120572-converting enzyme (TACE) [50] Thus loss of miR-122 expression in patients with liver cancer is correlated withthe presence of metastasis and a shorter time to recurrence[51]

While some miRNAs can inhibit angiogenesis othermiRNAs can stimulate new vessel formation MiR-126 anendothelial-specific miRNA can modulate VEGF levels andendothelial cell proliferation whereas knockout of miR-126leads to loss of vascular integrity and neoangiogenesis [5455] MiR-296 can modulate the expression of VEGF receptor2 and platelet-derived growth factor (PDGF) receptor 120573by directly targeting the hepatocyte growth factor-regulatedtyrosine kinase substrate (HGS) whichmediates degradationof the growth factor receptors [112] The miR-17-92 clusterwhich contains miR-17 miR-18 miR-19a miR-19b-1 20a andmiR-92-1 is the first oncogenic miRNAs identified in human[113] Although the major known function of the miR-17-92cluster is related to transcriptional factors c-Myc E2F andtheir autoregulatory loop [66 67] this cluster also enhancestumor angiogenesis by targeting thrombospondin-1 (TSP1)connective tissue growth factor (CTGF) and a number ofproangiogenic targets [109]

42 miRNAs Modulate Metastasis Several miRNAs are alsoinvolved in the metastasis through the regulation of EMTFive members of the miR-200 family (miR-200a miR-200b miR-200c miR-141 and miR-429) and miR-205 areable to increase E-cadherin expression decrease vimentinexpression inhibit EMT and prevent migration and invasionof cancer cells [57 58] MiR-155 expression is increased

in cancer cells and plays a positive role in transforminggrowth factor (TGF) 120573-induced EMT and cell migration andinvasion by targeting Ras homolog gene family member A(RhoA) [71] By downregulating Rho-associated coiled-coilcontaining protein kinase 2 (ROCK2) and histone-lysine N-methyltransferase (EZH2) miR-124 represses cytoskeletonreorganization and EMT ultimately inhibiting the invasiveandor metastatic potential of HCC [52] MiR-29a canpromote EMT and cancer metastasis in cooperation withoncogenic Ras signaling by repressing the expression oftristetraprolin (TTP) a protein involved in the degradation ofmessenger RNAs with AU-rich 31015840-untranslated regions [46]

It is possible that miRNAs that regulate cell proliferationand apoptosis have critical roles in cancer cell survival andarrest in the circulation duringmetastasis process [114] MiR-126 expression is often downregulated in cancers and is ableto decrease leukocyte and possibly cancer cell adherence toendothelial cells by targeting vascular cell adhesion molecule(VCAM)-1 on endothelial cells [56] In addition manymiRNAs have been discovered to play important roles inmodulation of T and B lymphocytes activation innate andadaptive immune responses [115] MiR-155 is required in con-ventional and regulatory T lymphocyte differentiation andactivation B lymphocyte development and TLR response[115] Cancer suppressing miR-146a can regulate TLR andcytokine signaling through a negative feedback regulation ofTNF receptor-associated factor 6 (TRAF6) and IL-1 receptor-associated kinase 1 (IRAK1) genes [59] MiR-150 miR-17sim92clusters andmiR-181 are important regulators of the immunesystem and therefore could participate in cell survival andarrest in circulation [115 116]

The interacting network of the key miRNAs and theirtarget genes in HCC initiation and progression is shown inFigure 2

5 miRNAs as Therapeutic Targets for HCC

51 miRNAs as Diagnostic Markers for HCC Sensitive andspecific cancer biomarkers are essential for early detectionand diagnosis of HCC as well as for developing preven-tive screening However current methods are insufficientfor detecting HCC at early stages Advances in magneticresonance imaging and computed tomography have greatlyimproved imaging of focal hypervascular masses consistentwith HCC but these procedures are costly and not readilyavailable in developing countries Laboratory data includingserum alfa-fetoprotein (AFP) and des-gamma carboxypro-thrombin (DCP) levels have been used as HCC biomarkersfor a long time However the accuracy of AFP is modest(sensitivity 39ndash65 specificity 76ndash94) One-third of casesof early-stage HCC (tumors lt 3 cm) are missed using AFPanalysis [117] and serum AFP levels are also elevated inpatients with benign liver diseases such as hepatitis andcirrhosis [118 119]

Many miRNAs are dysregulated in HCC thus it is to beexpected that circulating miRNA levels are also affected byHCCprogressionThehigh stability ofmiRNAs in circulationmakes them perfect biomarkers especially for detection of


PromotingInhibiting

miR-15a miR-16-1miR-221

miR-17

miR-18

miR-19

miR-20a

p27 p57

ET-1 CyclinD1 CDK6 CyclinG1 mTOR c-myc E2F

miR-1miR-92-1

miR-26a

miR-34amiR-195

miR-122

miR-7 miR-199

(a) Proliferation

miR-15amiR-16-1

miR-221

miR-25miR-93 miR-106

miR-224

Bim

miR-29miR-125

miR-122

Bmf Bcl-2 Bcl-w

PromotingInhibiting

(b) Apoptosis

PromotingInhibiting


miR-216

miR-221

miR-222

miR-519

miR-1

miR-34a

miR-198

miR-449

miR-141

miR-29amiR-126

miR-200

c-Met EMT VEGF

RhoA PTEN

(c) Metastasis

Figure 2 The interacting network of the key aberrant miRNAs and their target genes in HCC initiation and progression Downregulatedtumor suppressing miRNAs in HCC are indicated in black ellipse and upregulated oncogenic miRNAs are indicated in white ellipse Targetgenes having a positive effect on the cell process are indicated in white circle while genes having a negative effect are indicated in black circle

early stage presymptomatic diseases [120] It is interestingthat circulating miR-21 [121 122] miR-222 [122] and miR-223 [123] were found to be upregulated in the serumplasmaof HCC patients associated with HBV or HCV CirculatingmiR-21 level was significantly higher in HCC patients thanin those with chronic hepatitis and healthy controls Receiveroperating characteristic (ROC) analysis of miR-21 yielded anarea under the curve (AUC) of 0773 when differentiatingHCC from chronic hepatitis and an AUC of 0953 whendifferentiating HCC from healthy control Both sets of valueswere superior to AFP as biomarker in HCC [123] At thesame time serum levels ofmiR-1 miR-25 miR-92a miR-206miR-375 and let-7f were also significantly elevated in HCCpatients [124]

Serum miR-15b and miR-130b levels were also foundto be upregulated in HCC [125] MiR-130b had the largestarea under the curve (0913) with a sensitivity of 877and a specificity of 814 for detecting HCC and miR-15b had the highest sensitivity for detecting HCC of the

miRNAs examined (983) although its specificity was verylow (153) The high sensitivity of circulating miR-15b andmiR-130b as biomarkers for HCC holds promise for patientswith early-stage HCC who may have low AFP levels despitethe presence of disease Similarly serum miR-16 was foundto be a more sensitive biomarker for HCC than serum AFPand DCP levels [126]The combination of miR-16 AFP AFP-L3 andDCP yielded the optimal combination of sensitivity(924) and specificity (785) for HCC overall and whenanalysis was restricted to patients with tumors size smallerthan 3 cm [127] In addition a recent meta-analysis in whicheight studies were included showed the diagnostic value ofmiRNAs for HCC as follows pooled sensitivity 087 (072ndash098) pooled specificity 090 (076ndash100) pooled positivelikelihood ratio 87 (352ndash9745) pooled negative likelihoodratio 013 (002ndash031) and pooled diagnostic odds ratio 8669(1906ndash264600) [128]

Although the sensitivity and stability of miRNAs asbiomarkers are suitable for a clinical setting appropriate


controls need to be used in a research setting becauseHCC is often accompanied by viral hepatitis cirrhosis orother underlying liver conditions [37] When assessing thespecificity of a miRNA for detecting HCC it is critical toensure that patients and controls are matched not only by ageand sex but also by the etiology and severity of the underlyingliver disease

52 miRNAs in HCC Therapy There is now accumulatedevidence indicating that strategies based on modulation ofmiRNA activity could be a novel approach to cancer therapyPrevious studies have demonstrated that inhibition of miR-122 by administration of anti-miRNA oligonucleotides innonhuman primates is a promising approach for reducingmiRNA activity in the adult liver without toxicity [129]Theseproofs of principle established the basis for the various studiesthat have been performed in cancer models in vivo Anotherstudy has demonstrated that restoration of tumor suppressivemiR-122 makes HCC cells more sensitive to sorafenib treat-ment via downregulation of multidrug resistance genes [130]Conversely suppression of oncogenic miR-221 by antago-miRs resulted in prolonged survival and significant reductionin the number and size of tumors in comparison withuntreated animals [131] Similarly HCC cells transfected withanti-miR-21were significantly sensitive to chemotherapywithcombined interferon-120572 and 5-FU [132]

Recently the first miRNA-targeted drug a moleculeknown as miravirsen SPC3649 has been used in variousphase I studies and is currently in a phase II trial for thetreatment of chronic hepatitis C [133] This trial stemmedfrom the discovery of involvement of miR-122 in HCV RNAaccumulation showing that treatment of chronically infectednonhuman primates with an locked nucleic acid (LNA)-modified anti-miR-122 oligonucleotidewaswell tolerated andled to long-lasting suppression of HCV viremia [134 135]

6 Conclusion

In this review we summarize the role of miRNAs in car-cinogenesis and progression of HCC as well as the diagnosticand therapeutic potential in some miRNAs Collectively theinvestigative studies performed till now have resulted in abetter understanding of cancer-relatedmiRNA functions andtheir roles as tumor suppressors and oncogenes Given theimplication of a large number of miRNAs in the controlof key tumor suppressors and oncogenes the deregulationof specific miRNAs has been shown to greatly influenceHCC development invasiveness prognosis and treatmentresponse From a diagnostic point of view high stabilityof miRNAs in circulation makes them perfect biomarkersHowever lack of studies on preneoplastic and early neoplasticlesions does not allow to discriminate whichmiRNAs are realdrivers of the carcinogenic process In addition the discoveryof aberrantmiRNAs and their corresponding targets has con-tributed to the development ofmiRNA-based therapeutics forHCC Although technological advances indicate that the useof miRNAs or antagomir as therapeutics is feasible and safe

more studies are still needed to move this field forward intothe clinical setting

Conflict of Interests

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

Acknowledgment

This study was supported in part by contract GrantsCLRPG8B0052 and CMRPG 8C0971 from Chang GungMemorial Hospital Taiwan

References

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[2] M Schwartz S Roayaie andM Konstadoulakis ldquoStrategies forthe management of hepatocellular carcinomardquo Nature ClinicalPractice Oncology vol 4 no 7 pp 424ndash432 2007

[3] R T-P Poon and S-T Fan ldquoHepatectomy for hepatocellularcarcinoma patient selection and postoperative outcomerdquo LiverTransplantation vol 10 supplement 1 no 2 pp S39ndashS45 2004

[4] M-F Yuen C-C Cheng I J Lauder S-K Lam C G-COoi and C-L Lai ldquoEarly detection of hepatocellular carcinomaincreases the chance of treatment Hong Kong experiencerdquoHepatology vol 31 no 2 pp 330ndash335 2000

[5] S Fukuda T Itamoto H Nakahara et al ldquoClinicopathologicfeatures and prognostic factors of resected solitary small-sizedhepatocellular carcinomardquoHepato-Gastroenterology vol 52 no64 pp 1163ndash1167 2005

[6] M-W Yu and C-J Chen ldquoHepatitis B and C viruses in thedevelopment of hepatocellular carcinomardquo Critical Reviews inOncologyHematology vol 17 no 2 pp 71ndash91 1994

[7] W-L ChuangW-Y Chang S-N Lu et al ldquoThe role of hepatitisB and C viruses in hepatocellular carcinoma in a hepatitis Bendemic area a case-control studyrdquo Cancer vol 69 no 8 pp2052ndash2054 1992

[8] C-H Hung C-H Chen C-M Lee et al ldquoRole of viral geno-types and hepatitis B viral mutants in the risk of hepatocellularcarcinoma associated with hepatitis B and C dual infectionrdquoIntervirology vol 56 no 5 pp 316ndash324 2013

[9] T M Welzel B I Graubard S Zeuzem H B El-Serag J ADavila and K A Mcglynn ldquoMetabolic syndrome increases therisk of primary liver cancer in the United States a study in theSEER-medicare databaserdquo Hepatology vol 54 no 2 pp 463ndash471 2011

[10] J Bruix and M Sherman ldquoManagement of hepatocellularcarcinoma an updaterdquoHepatology vol 53 no 3 pp 1020ndash10222011

[11] R N Aravalli C J Steer and E N K Cressman ldquoMolecularmechanisms of hepatocellular carcinomardquo Hepatology vol 48no 6 pp 2047ndash2063 2008

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[13] H Guo N T Ingolia J S Weissman and D P BartelldquoMammalian microRNAs predominantly act to decrease targetmRNA levelsrdquo Nature vol 466 no 7308 pp 835ndash840 2010


[14] V Ambros ldquoThe functions of animal microRNAsrdquo Nature vol431 no 7006 pp 350ndash355 2004

[15] R Grassmann and K-T Jeang ldquoThe roles of microRNAs inmammalian virus infectionrdquo Biochimica et Biophysica ActamdashGeneRegulatoryMechanisms vol 1779 no 11 pp 706ndash711 2008

[16] E Gottwein and B R Cullen ldquoViral and cellular microRNAsas determinants of viral pathogenesis and immunityrdquo Cell Hostand Microbe vol 3 no 6 pp 375ndash387 2008

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[18] A Lujambio and S W Lowe ldquoThe microcosmos of cancerrdquoNature vol 482 no 321 pp 347ndash355 2012

[19] J W F Catto A Alcaraz A S Bjartell et al ldquoMicroRNAin prostate bladder and kidney cancer a systematic reviewrdquoEuropean Urology vol 59 no 5 pp 671ndash681 2011

[20] C Corcoran A M Friel M J Duffy J Crown and LOrsquoDriscoll ldquoIntracellular and extracellularmicroRNAs in breastcancerrdquo Clinical Chemistry vol 57 no 1 pp 18ndash32 2011

[21] B Song and J Ju ldquoImpact of miRNAs in gastrointestinalcancer diagnosis and prognosisrdquo Expert Reviews in MolecularMedicine vol 12 article e33 2010

[22] H K Saini S Griffiths-Jones and A J Enright ldquoGenomicanalysis of human microRNA transcriptsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 45 pp 17719ndash17724 2007

[23] S M Hammond E Bernstein D Beach and G J HannonldquoAn RNA-directed nuclease mediates post-transcriptional genesilencing in Drosophila cellsrdquo Nature vol 404 no 6775 pp293ndash296 2000

[24] Y Tay J Zhang A M Thomson B Lim and I RigoutsosldquoMicroRNAs toNanogOct4 and Sox2 coding regionsmodulateembryonic stem cell differentiationrdquo Nature vol 455 no 7216pp 1124ndash1128 2008

[25] J R Lytle T A Yario and J A Steitz ldquoTarget mRNAs arerepressed as efficiently by microRNA-binding sites in the 51015840UTR as in the 31015840 UTRrdquo Proceedings of the National Academyof Sciences of the United States of America vol 104 no 23 pp9667ndash9672 2007

[26] S Vasudevan Y Tong and J A Steitz ldquoSwitching from repres-sion to activation microRNAs can up-regulate translationrdquoScience vol 318 no 5858 pp 1931ndash1934 2007

[27] A M Eiring J G Harb P Neviani et al ldquomiR-328 functionsas an RNA decoy to modulate hnRNP E2 regulation of mRNAtranslation in leukemic blastsrdquo Cell vol 140 no 5 pp 652ndash6652010

[28] 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

[29] P S Mitchell R K Parkin E M Kroh et al ldquoCirculatingmicroRNAs as stable blood-based markers for cancer detec-tionrdquo Proceedings of the National Academy of Sciences of theUnited States of America vol 105 no 30 pp 10513ndash10518 2008

[30] 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

[31] 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 423ndash433 2011

[32] A E Pasquinelli ldquoMicroRNAs and their targets recognitionregulation and an emerging reciprocal relationshiprdquo NatureReviews Genetics vol 13 no 4 pp 271ndash282 2012

[33] S Chatterjee M Fasler I Bussing and H Groszlighans ldquoTarget-mediated protection of endogenous microRNAs in C elegansrdquoDevelopmental Cell vol 20 no 3 pp 388ndash396 2011

[34] S L Ameres M D Horwich J-H Hung et al ldquoTarget RNA-directed trimming and tailing of small silencing RNAsrdquo Sciencevol 328 no 5985 pp 1534ndash1539 2010

[35] P-S Chen J-L Su S-T Cha et al ldquomiR-107 promotes tumorprogression by targeting the let-7 microRNA in mice andhumansrdquoThe Journal of Clinical Investigation vol 121 no 9 pp3442ndash3455 2011

[36] R Tang L Li D Zhu D Hou T Cao H Gu et al ldquoMousemiRNA-709 directly regulates miRNA-15a16-1 biogenesis atthe posttranscriptional level in the nucleus evidence for amicroRNA hierarchy systemrdquo Cell Research vol 22 no 3 pp504ndash515 2012

[37] X W Wang N H Heegaard and H Orum ldquoMicroRNAs inliver diseaserdquo Gastroenterology vol 142 no 7 pp 1431ndash14432012

[38] T Ogawa M Enomoto H Fujii et al ldquoMicroRNA-221222upregulation indicates the activation of stellate cells and theprogression of liver fibrosisrdquo Gut vol 61 no 11 pp 1600ndash16092012

[39] R T Marquez S Bandyopadhyay E B Wendlandt et alldquoCorrelation between microRNA expression levels and clinicalparameters associated with chronic hepatitis C viral infection inhumansrdquo Laboratory Investigation vol 90 no 12 pp 1727ndash17362010

[40] V Bihrer M Friedrich-Rust B Kronenberger et al ldquoSerummiR-122 as a biomarker of necroinflammation in patients withchronic hepatitis C virus infectionrdquo The American Journal ofGastroenterology vol 106 no 9 pp 1663ndash1669 2011

[41] J Datta H Kutay M W Nasser et al ldquoMethylation mediatedsilencing of microRNA-1 gene and its role in hepatocellularcarcinogenesisrdquoCancer Research vol 68 no 13 pp 5049ndash50582008

[42] Y Fang J-L Xue Q Shen J Chen and L Tian ldquoMicroRNA-7inhibits tumor growth andmetastasis by targeting the phospho-inositide 3-kinaseAkt pathway in hepatocellular carcinomardquoHepatology vol 55 no 6 pp 1852ndash1862 2012

[43] T Xu Y Zhu Y Xiong Y-Y Ge J-P Yun and S-M ZhuangldquoMicroRNA-195 suppresses tumorigenicity and regulates G1Stransition of human hepatocellular carcinoma cellsrdquo Hepatol-ogy vol 50 no 1 pp 113ndash121 2009

[44] J Kota R R Chivukula K A OrsquoDonnell et al ldquoTherapeuticmicroRNA delivery suppresses tumorigenesis in a murine livercancer modelrdquo Cell vol 137 no 6 pp 1005ndash1017 2009

[45] Y Xiong J-H Fang J-P Yun et al ldquoEffects of microRNA-29on apoptosis tumorigenicity and prognosis of hepatocellularcarcinomardquo Hepatology vol 51 no 3 pp 836ndash845 2010

[46] C A Gebeshuber K Zatloukal and J Martinez ldquomiR-29asuppresses tristetraprolin which is a regulator of epithelialpolarity and metastasisrdquo EMBO Reports vol 10 no 4 pp 400ndash405 2009

[47] J Cheng L Zhou Q-F Xie et al ldquoThe impact of miR-34aon protein output in hepatocellular carcinoma HepG2 cellsrdquoProteomics vol 10 no 8 pp 1557ndash1572 2010

[48] N Li H Fu Y Tie et al ldquomiR-34a inhibits migration andinvasion by down-regulation of c-Met expression in human


hepatocellular carcinoma cellsrdquo Cancer Letters vol 275 no 1pp 44ndash53 2009

[49] L Gramantieri M Ferracin F Fornari et al ldquoCyclin G1 is atarget of miR-122a a microRNA frequently down-regulated inhuman hepatocellular carcinomardquo Cancer Research vol 67 no13 pp 6092ndash6099 2007

[50] W-C Tsai P W-C Hsu T-C Lai et al ldquoMicroRNA-122a tumor suppressor microRNA that regulates intrahepaticmetastasis of hepatocellular carcinomardquoHepatology vol 49 no5 pp 1571ndash1582 2009

[51] C Coulouarn V M Factor J B Andersen M E Durkin andS S Thorgeirsson ldquoLoss of miR-122 expression in liver cancercorrelateswith suppression of the hepatic phenotype and gain ofmetastatic propertiesrdquoOncogene vol 28 no 40 pp 3526ndash35362009

[52] F Zheng Y-J Liao M-Y Cai et al ldquoThe putative tumoursuppressormicroRNA-124modulates hepatocellular carcinomacell aggressiveness by repressing ROCK2 and EZH2rdquo Gut vol61 no 2 pp 278ndash289 2012

[53] A Zhao Q Zeng X Xie et al ldquoMicroRNA-125b induces cancercell apoptosis through suppression of Bcl-2 expressionrdquo Journalof Genetics and Genomics vol 39 no 1 pp 29ndash35 2012

[54] S Wang A B Aurora B A Johnson et al ldquoThe endothelial-specific microRNA miR-126 governs vascular integrity andangiogenesisrdquo Developmental Cell vol 15 no 2 pp 261ndash2712008

[55] J E Fish M M Santoro S U Morton et al ldquomiR-126 regulatesangiogenic signaling and vascular integrityrdquo DevelopmentalCell vol 15 no 2 pp 272ndash284 2008

[56] T A Harris M Yamakuchi M Ferlito J T Mendell and CJ Lowenstein ldquoMicroRNA-126 regulates endothelial expressionof vascular cell adhesionmolecule 1rdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 105 no5 pp 1516ndash1521 2008

[57] G JHurteau J A Carlson SD Spivack andG J Brock ldquoOver-expression of the microRNA hsa-miR-200c leads to reducedexpression of transcription factor 8 and increased expressionof E-cadherinrdquo Cancer Research vol 67 no 17 pp 7972ndash79762007

[58] P A Gregory A G Bert E L Paterson et al ldquoThe miR-200 family and miR-205 regulate epithelial to mesenchymaltransition by targeting ZEB1 and SIP1rdquo Nature Cell Biology vol10 no 5 pp 593ndash601 2008

[59] KD TaganovM P Boldin K-J Chang andD Baltimore ldquoNF-120581B-dependent induction of microRNA miR-146 an inhibitortargeted to signaling proteins of innate immune responsesrdquoProceedings of the National Academy of Sciences of the UnitedStates of America vol 103 no 33 pp 12481ndash12486 2006

[60] S Tan R Li K Ding P E Lobie and T Zhu ldquoMiR-198 inhibitsmigration and invasion of hepatocellular carcinoma cells bytargeting the HGFc-MET pathwayrdquoThe FEBS Letters vol 585no 14 pp 2229ndash2234 2011

[61] Y Murakami T Yasuda K Saigo et al ldquoComprehensiveanalysis of microRNA expression patterns in hepatocellularcarcinoma and non-tumorous tissuesrdquoOncogene vol 25 no 17pp 2537ndash2545 2006

[62] J Jiang Y Gusev I Aderca et al ldquoAssociation of microRNAexpression in hepatocellular carcinomas with hepatitis infec-tion cirrhosis and patient survivalrdquo Clinical Cancer Researchvol 14 no 2 pp 419ndash427 2008

[63] F Fornari M Milazzo P Chieco et al ldquoMiR-199a-3p regulatesmTOR and c-Met to influence the doxorubicin sensitivity of

human hepatocarcinoma cellsrdquo Cancer Research vol 70 no 12pp 5184ndash5193 2010

[64] R Buurman E Gurlevik V Schaffer et al ldquoHistone deacety-lases activate hepatocyte growth factor signaling by repressingmicroRNA-449 in hepatocellular carcinoma cellsrdquo Gastroen-terology vol 143 no 3 pp 811ndash820 2012

[65] D Bonci V Coppola M Musumeci et al ldquoThe miR-15a-miR-16-1 cluster controls prostate cancer by targeting multipleoncogenic activitiesrdquo Nature Medicine vol 14 no 11 pp 1271ndash1277 2008

[66] Y Sylvestre V de Guire E Querido et al ldquoAn E2FmiR-20a autoregulatory feedback looprdquo The Journal of BiologicalChemistry vol 282 no 4 pp 2135ndash2143 2007

[67] B D Aguda Y Kim M G Piper-Hunter A Friedman andC B Marsh ldquoMicroRNA regulation of a cancer networkconsequences of the feedback loops involving miR-17-92 E2FandMycrdquo Proceedings of the National Academy of Sciences of theUnited States of America vol 105 no 50 pp 19678ndash19683 2008

[68] F Meng R Henson H Wehbe-Janek K Ghoshal S TJacob and T Patel ldquoMicroRNA-21 regulates expression of thePTEN tumor suppressor gene in human hepatocellular cancerrdquoGastroenterology vol 133 no 2 pp 647ndash658 2007

[69] Y Li W Tan T W L Neo et al ldquoRole of the miR-106b-25microRNAcluster in hepatocellular carcinomardquoCancer Sciencevol 100 no 7 pp 1234ndash1242 2009

[70] K Yuan Z Lian B Sun M M Clayton I O L Ng andM A Feitelson ldquoRole of miR-148a in hepatitis B associatedhepatocellular carcinomardquo PLoS ONE vol 7 no 4 Article IDe35331 2012

[71] W Kong H Yang L He et al ldquoMicroRNA-155 is regu-lated by the transforming growth factor 120573Smad pathway andcontributes to epithelial cell plasticity by targeting RhoArdquoMolecular and Cellular Biology vol 28 no 22 pp 6773ndash67842008

[72] K Wu J Ding C Chen et al ldquoHepatic transforming growthfactor beta gives rise to tumor-initiating cells and promotes livercancer developmentrdquo Hepatology vol 56 no 6 pp 2255ndash22672012

[73] Q W-L Wong R W-M Lung P T-Y Law et al ldquoMicroRNA-223 is commonly repressed in hepatocellular carcinoma andpotentiates expression of Stathmin1rdquo Gastroenterology vol 135no 1 pp 257ndash269 2008

[74] M Garofalo G di Leva G Romano et al ldquomiR-221amp222regulate TRAIL resistance and enhance tumorigenicity throughPTEN and TIMP3 downregulationrdquo Cancer Cell vol 16 no 6pp 498ndash509 2009

[75] A J Schetter S Y Leung J J Sohn et al ldquoMicroRNAexpressionprofiles associated with prognosis and therapeutic outcomein colon adenocarcinomardquo Journal of the American MedicalAssociation vol 299 no 4 pp 425ndash436 2008

[76] L Gramantieri F Fornari M Ferracin et al ldquoMicroRNA-221targets Bmf in hepatocellular carcinoma and correlates withtumormultifocalityrdquoClinical Cancer Research vol 15 no 16 pp5073ndash5081 2009

[77] Y Suarez C Fernandez-Hernando J S Pober andW C SessaldquoDicer dependent microRNAs regulate gene expression andfunctions in human endothelial cellsrdquo Circulation Research vol100 no 8 pp 1164ndash1173 2007

[78] Q W-L Wong A K-K Ching A W-H Chan et al ldquomiR-222 overexpression confers cellmigratory advantages in hepato-cellular carcinoma through enhancing AKT signalingrdquo ClinicalCancer Research vol 16 no 3 pp 867ndash875 2010


[79] Y Zhang S Takahashi A Tasaka T Yoshima H Ochi and KChayama ldquoInvolvement of microRNA-224 in cell proliferationmigration invasion and anti-apoptosis in hepatocellular carci-nomardquo Journal of Gastroenterology and Hepatology vol 28 no3 pp 565ndash575 2013

[80] F Fornari M Milazzo P Chieco et al ldquoIn hepatocellular carci-nomamiR-519d is up-regulated by p53 and DNA hypomethyla-tion and targets CDKN1Ap21 PTEN AKT3 and TIMP2rdquo TheJournal of Pathology vol 227 no 3 pp 275ndash285 2012

[81] J Hou L Lin W Zhou et al ldquoIdentification of miRNomes inhuman liver and hepatocellular carcinoma reveals miR-199ab-3p as therapeutic target for hepatocellular carcinomardquo CancerCell vol 19 no 2 pp 232ndash243 2011

[82] K Morita A Taketomi K Shirabe et al ldquoClinical significanceand potential of hepatic microRNA-122 expression in hepatitisCrdquo Liver International vol 31 no 4 pp 474ndash484 2011

[83] J Chang E Nicolas D Marks et al ldquomiR-122 a mammalianliver-specificmicroRNA is processed from hcrmRNA andmaydownregulate the high affinity cationic amino acid transporterCAT-1rdquo RNA Biology vol 1 no 2 pp 106ndash113 2004

[84] S H Hsu B Wang J Kota et al ldquoEssential metabolic anti-inflammatory and anti-tumorigenic functions of miR-122 inliverrdquo The Journal of Clinical Investigation vol 122 no 8 pp2871ndash2883 2012

[85] W C Tsai S D Hsu C S Hsu et al ldquoMicroRNA-122 plays acritical role in liver homeostasis and hepatocarcinogenesisrdquoTheJournal of Clinical Investigation vol 122 no 8 pp 2884ndash28972012

[86] F Fornari L Gramantieri C Giovannini et al ldquoMiR-122cyclinG1 interaction modulates p53 activity and affects doxorubicinsensitivity of human hepatocarcinoma cellsrdquo Cancer Researchvol 69 no 14 pp 5761ndash5767 2009

[87] M R Jensen VM Factor A Fantozzi KHelin C-GHuh andS S Thorgeirsson ldquoReduced hepatic tumor incidence in cyclinG1-deficient micerdquoHepatology vol 37 no 4 pp 862ndash870 2003

[88] X Q Jia H Q Cheng X Qian et al ldquoLentivirus-mediatedoverexpression of microRNA-199a inhibits cell proliferationof human hepatocellular carcinomardquo Cell Biochemistry andBiophysics vol 62 no 1 pp 237ndash244 2012

[89] S Kim U J Lee M N Kim et al ldquoMicroRNA miR-199alowast regulates the MET proto-oncogene and the downstreamextracellular signal-regulated kinase 2 (ERK2)rdquo The Journal ofBiological Chemistry vol 283 no 26 pp 18158ndash18166 2008

[90] J C Henry J-K Park J Jiang et al ldquoMiR-199a-3p targetsCD44 and reduces proliferation of CD44 positive hepatocellu-lar carcinoma cell linesrdquo Biochemical and Biophysical ResearchCommunications vol 403 no 1 pp 120ndash125 2010

[91] F Fornari L Gramantieri M Ferracin et al ldquoMiR-221 controlsCDKN1Cp57 and CDKN1Bp27 expression in human hepato-cellular carcinomardquo Oncogene vol 27 no 43 pp 5651ndash56612008

[92] R Medina S K Zaidi C-G Liu et al ldquoMicroRNAs 221 and222 bypass quiescence and compromise cell survivalrdquo CancerResearch vol 68 no 8 pp 2773ndash2780 2008

[93] J A Chan A M Krichevsky and K S Kosik ldquoMicroRNA-21is an antiapoptotic factor in human glioblastoma cellsrdquo CancerResearch vol 65 no 14 pp 6029ndash6033 2005

[94] M-L Si S Zhu H Wu Z Lu F Wu and Y-Y Mo ldquomiR-21-mediated tumor growthrdquo Oncogene vol 26 no 19 pp 2799ndash2803 2007

[95] M Garofalo C Quintavalle G Romano C M Croce and GCondorelli ldquoMiR221222 in cancer their role in tumor progres-sion and response to therapyrdquo Current Molecular Medicine vol12 no 1 pp 27ndash33 2012

[96] 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

[97] Q Yuan K Loya B Rani et al ldquoMicroRNA-221 overexpressionaccelerates hepatocyte proliferation during liver regenerationrdquoHepatology vol 57 no 1 pp 299ndash310 2013

[98] G-J Wu C Sinclair S Hinson J N Ingle P C Roche and F JCouch ldquoStructural analysis of the 17q22-23 amplicon identifiesseveral independent targets of amplification in breast cancer celllines and tumorsrdquoCancer Research vol 61 no 13 pp 4951ndash49552001

[99] K Kasahara T Taguchi I Yamasaki M Kamada K Yuri andT Shuin ldquoDetection of genetic alterations in advanced prostatecancer by comparative genomic hybridizationrdquoCancer Geneticsand Cytogenetics vol 137 no 1 pp 59ndash63 2002

[100] S Fujita T Ito T Mizutani et al ldquomiR-21 gene expression trig-gered by AP-1 is sustained through a double-negative feedbackmechanismrdquo Journal of Molecular Biology vol 378 no 3 pp492ndash504 2008

[101] J Ribas and S E Lupold ldquoThe transcriptional regulationof miR-21 its multiple transcripts and their implication inprostate cancerrdquo Cell Cycle vol 9 no 5 pp 923ndash929 2010

[102] P Bhat-Nakshatri G Wang N R Collins et al ldquoEstradiol-regulated microRNAs control estradiol response in breast can-cer cellsrdquo Nucleic Acids Research vol 37 no 14 pp 4850ndash48612009

[103] L Zhou Z X Yang W J Song et al ldquoMicroRNA-21 regulatesthe migration and invasion of a stem-like population in hepa-tocellular carcinomardquo International Journal of Oncology vol 43no 2 pp 661ndash669 2013

[104] L Bao Y Yan C Xu et al ldquoMicroRNA-21 suppresses PTENand hSulf-1 expression and promotes hepatocellular carcinomaprogression through AKTERK pathwaysrdquo Cancer Letters vol337 no 2 pp 226ndash236 2013

[105] C Xu S Liu H Fu et al ldquoMicroRNA-193b regulates pro-liferation migration and invasion in human hepatocellularcarcinoma cellsrdquo European Journal of Cancer vol 46 no 15 pp2828ndash2836 2010

[106] W Zhang G Kong J Zhang T Wang L Ye and X ZhangldquoMicroRNA-520b inhibits growth of hepatoma cells by target-ing MEKK2 and cyclin D1rdquo PLoS ONE vol 7 no 2 Article IDe31450 2012

[107] C J-F Lin H-Y Gong H-C Tseng W-L Wang and J-L Wu ldquomiR-122 targets an anti-apoptotic gene Bcl-w inhuman hepatocellular carcinoma cell linesrdquo Biochemical andBiophysical Research Communications vol 375 no 3 pp 315ndash320 2008

[108] Y Suarez and W C Sessa ldquoMicroRNAs as novel regulators ofangiogenesisrdquoCirculation Research vol 104 no 4 pp 442ndash4542009

[109] A Bonauer G Carmona M Iwasaki et al ldquoMicroRNA-92acontrols angiogenesis and functional recovery of ischemictissues in micerdquo Science vol 324 no 5935 pp 1710ndash1713 2009

[110] Y Chen and D H Gorski ldquoRegulation of angiogenesis througha microRNA (miR-130a) that down-regulates antiangiogenichomeobox genes GAX and HOXA5rdquo Blood vol 111 no 3 pp1217ndash1226 2008


[111] L Poliseno A Tuccoli L Mariani et al ldquoMicroRNAsmodulatethe angiogenic properties of HUVECsrdquo Blood vol 108 no 9pp 3068ndash3071 2006

[112] T Wurdinger B A Tannous O Saydam et al ldquomiR-296regulates growth factor receptor overexpression in angiogenicendothelial cellsrdquo Cancer Cell vol 14 no 5 pp 382ndash393 2008

[113] Y Hayashita H Osada Y Tatematsu et al ldquoA polycistronicmicroRNA cluster miR-17-92 is overexpressed in human lungcancers and enhances cell proliferationrdquo Cancer Research vol65 no 21 pp 9628ndash9632 2005

[114] R Schickel B Boyerinas S-M Park andM E Peter ldquoMicroR-NAs key players in the immune system differentiation tumori-genesis and cell deathrdquoOncogene vol 27 no 45 pp 5959ndash59742008

[115] J Dooley M A Linterman and A Liston ldquoMicroRNA regu-lation of T-cell developmentrdquo Immunological Reviews vol 253no 1 pp 53ndash64 2013

[116] K-J Rhee S Wu X Wu et al ldquoInduction of persistent colitisby a human commensal enterotoxigenic Bacteroides fragilis inwild-type C57BL6micerdquo Infection and Immunity vol 77 no 4pp 1708ndash1718 2009

[117] J Collier and M Sherman ldquoScreening for hepatocellular carci-nomardquo Hepatology vol 27 no 1 pp 273ndash278 1998

[118] H Oka A Tamori T Kuroki K Kobayashi and S YamamotoldquoProspective study of 120572-fetoprotein in cirrhotic patients mon-itored for development of hepatocellular carcinomardquo Hepatol-ogy vol 19 no 1 pp 61ndash66 1994

[119] MAAbdalla andYHaj-Ahmad ldquoPromising candidate urinarymicroRNA biomarkers for the early detection of hepatocellularcarcinoma amonghigh-risk hepatitis C virus Egyptian patientsrdquoJournal of Cancer vol 3 pp 19ndash31 2012

[120] A Petrelli A Perra D Cora et al ldquoMicroRNAgene profilingunveils early molecular changes and nuclear factor erythroidrelated factor 2 (NRF2) activation in a rat model recapitulatinghuman hepatocellular carcinoma (HCC)rdquo Hepatology vol 59no 1 pp 228ndash241 2014

[121] J Xu C Wu X Che et al ldquoCirculating microRNAs miR-21 miR-122 and miR-223 in patients with hepatocellularcarcinoma or chronic hepatitisrdquo Molecular Carcinogenesis vol50 no 2 pp 136ndash142 2011

[122] J Li Y Wang W Yu J Chen and J Luo ldquoExpression ofserum miR-221 in human hepatocellular carcinoma and itsprognostic significancerdquo Biochemical and Biophysical ResearchCommunications vol 406 no 1 pp 70ndash73 2011

[123] Y Tomimaru H Eguchi H Nagano et al ldquoCirculatingmicroRNA-21 as a novel biomarker for hepatocellular carci-nomardquo Journal of Hepatology vol 56 no 1 pp 167ndash175 2012

[124] L-M Li Z-B Hu Z-X Zhou X Chen F-Y Liu and J-FZhang ldquoSerum microRNA profiles serve as novel biomarkersfor HBV infection and diagnosis of HBV-positive hepatocarci-nomardquo Cancer Research vol 70 no 23 pp 9798ndash9807 2010

[125] A M Liu T-J Yao W Wang et al ldquoCirculating miR-15band miR-130b in serum as potential markers for detectinghepatocellular carcinoma a retrospective cohort studyrdquo BMJOpen vol 2 no 2 article e000825 2012

[126] W Hou and H L Bonkovsky ldquoNon-coding RNAs in hep-atitis C-induced hepatocellular carcinoma dysregulation andimplications for early detection diagnosis and therapyrdquo WorldJournal of Gastroenterology vol 19 no 44 pp 7836ndash7845 2013

[127] K Z Qu K Zhang H Li N H Afdhal andM Albitar ldquoCircu-latingMicroRNAs as biomarkers for hepatocellular carcinomardquo

Journal of Clinical Gastroenterology vol 45 no 4 pp 355ndash3602011

[128] Q Y Hu H Jiang J Su and Y Q Jia ldquoMicroRNAs asbiomarkers for hepatocellular carcinoma a diagnostic meta-analysisrdquo Clinical Laboratory vol 59 no 9-10 pp 1113ndash11202013

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

[130] S Bai M W Nasser B Wang et al ldquoMicroRNA-122 inhibitstumorigenic properties of hepatocellular carcinoma cells andsensitizes these cells to sorafenibrdquo The Journal of BiologicalChemistry vol 284 no 46 pp 32015ndash32027 2009

[131] E Callegari B K Elamin F Giannone et al ldquoLiver tumori-genicity promoted by microRNA-221 in a mouse transgenicmodelrdquo Hepatology vol 56 no 3 pp 1025ndash1033 2012

[132] Y Tomimaru H Eguchi H Nagano et al ldquoMicroRNA-21induces resistance to the anti-tumour effect of interferon-1205725-fluorouracil in hepatocellular carcinoma cellsrdquo British Journalof Cancer vol 103 no 10 pp 1617ndash1626 2010

[133] M Lindowand SKauppinen ldquoDiscovering the firstmicroRNA-targeted drugrdquo The Journal of Cell Biology vol 199 no 3 pp407ndash412 2012

[134] R E Lanford E S Hildebrandt-Eriksen A Petri et al ldquoTher-apeutic silencing of microRNA-122 in primates with chronichepatitis C virus infectionrdquo Science vol 327 no 5962 pp 198ndash201 2010

[135] E S Hildebrandt-Eriksen V Aarup R Persson H F HansenM E Munk and H Orum ldquoA locked nucleic acid oligonu-cleotide targeting microRNA 122 is well-tolerated in cynomol-gus monkeysrdquo Nucleic AcidTherapeutics vol 22 no 3 pp 152ndash161 2012

Submit your manuscripts athttpwwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


MEDIATORSINFLAMMATION

of


Behavioural Neurology

EndocrinologyInternational Journal of



Disease Markers


BioMed Research International

OncologyJournal of



Oxidative Medicine and Cellular Longevity


PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

ObesityJournal of



Computational and Mathematical Methods in Medicine

OphthalmologyJournal of


Diabetes ResearchJournal of



Research and TreatmentAIDS


Gastroenterology Research and Practice


Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom


on the cellular function of their targets [18] Dysregulationof miRNAs in cancer has been repeatedly described forexample in prostate bladder and kidney cancer [19] breastcancer [20] and colon cancer [21]

This review will elaborate on the aberrant expressionof miRNAs in HCC and the pathological implications andmolecular functions of some well-characterized oncogenicand tumor suppressive miRNAs Furthermore we will dis-cuss the clinical prospect of miRNAs as diagnostic andprognostic biomarkers of HCC and their potential roles incancer treatment

2 miRNAs Generation and Function

21 miRNAs Biogenesis The generation of mature miRNAsis a multistep process that starts with the initial transcriptionof their genes by RNA polymerase II This results in longcapped and polyadenylated primary miRNAs of approxi-mately 1ndash4 kb [22] These transcripts are then cleaved by themicroprocessor complex which consists of the nuclease Dro-sha and the double-stranded RNA-binding protein DiGeorgesyndrome critical region gene 8 (DGCR8) into a precursormiRNA of 60ndash100 nucleotides The pre-miRNA is subse-quently transported from the nucleus to the cytoplasm byexportin 5 and further cleaved by the RNase enzyme Dicerinto double-stranded miRNAs [23] These two strands areseparated by helicases and the mature strand is incorporatedinto the RNA-induced silencing complex (RISC) The briefsummary of miRNA biogenesis is shown in Figure 1

Typically mature miRNAs regulate gene expressionthrough sequence-specific binding to the 31015840 UTR of a targetmRNA but recent evidence indicates that miRNAs can alsobind to other regions of a target mRNA [24 25]ThemiRNA-mRNA interaction usually causes translational repressionandor mRNA cleavage and thus reduces the final proteinoutput However this traditional understanding of miRNAsas negative regulators of gene expression has recently beenchallenged by the discovery of new and unexpected mech-anisms of action of miRNAs This includes evidence thatmiRNAs can also increase the translation of a target mRNAby recruiting protein complexes to the Adenylate-uridylate-(AU-) rich elements of the mRNA [26] or they can indirectlyincrease the target protein output by derepressing mRNAtranslation by interactingwith proteins that block the transla-tion of the target gene [27] Also there is evidence indicatingthat miRNAs can switch the regulation from repression toactivation of target gene translation in conditions of cell cyclearrest [26]

In addition to functioning within cells miRNAs areabundant in the bloodstream and can act at neighboring cellsand at more distant sites within the body in a hormone-like fashion suggesting that they can mediate both short-and long-range cell-cell communication [28 29] MiRNAstogether with RNA-binding proteins can be packaged andtransported extracellularly by exosomes or microvesicles [3031] Likewise miRNAs in the bloodstream can be taken upby the recipient cells via endocytosis and further bound tointracellular proteins such as toll-like receptors (TLR) [28]

Nucleus

Transcription

Processing

Exporting

Dicing

Incorporationinto RISC

miRNA gene

Pri-miRNA

Pre-miRNA

Pre-miRNA

miRNA duplex

Mature miRNA

RNA Pol II

Drosha-DGCR8

Exportin 5

Dicer

RISC

Cytoplasm

Figure 1 Brief summary in miRNA biogenesis (1) initial tran-scription by RNA polymerase (Pol II) into primary miRNA (pri-miRNA) (2) processing byDrosha-DGCR8 into a precursormiRNA(pre-miRNA) (3) export of the pre-miRNA via Exportin-5 from thenucleus to the cytoplasm (4) cleaved by theRNase enzymeDicer intodouble-stranded miRNAs (5) incorporation into the RNA-inducedsilencing complex (RISC)

22 miRNAs Regulation and Interaction Although miRNAstypically repress target gene expression recent work hasrevealed that regulation in the miRNA pathway is a two-way street Not only can base pairing between a miRNAand its target result in repressed target expression but theseinteractions can also have an impact on the levels of themiRNA [32] However the reciprocal effect of targets onmiRNAs remains entirely unclear In some cases targetinteractions offer a protective influence on miRNA stabilitywhereas in others the outcome is miRNA degradation [3334]

In addition to the binding between miRNA and 31015840UTR of its target mRNA recent studies have identified adirect interaction between two individual miRNAs throughsequence match [35 36] Chen et al provided functionalevidence of miRNA-miRNA interaction between miR-107and let-7 Using a mutation system they further identifiedthe essential role of an internal loop within the miR-107let-7 duplex which provided important clues for furtherinvestigation on the underlying mechanism [35] This newlydiscovered regulation sheds light on our current knowledgein the posttranscriptional control of miRNA Consideringthe interaction and the multifaceted roles of miRNA theregulation network of miRNA becomes more complex thanwe originally thought

3 miRNAs in Hepatocarcinogenesis

miRNAs fine-tune all physiological and many pathologicalprocesses that are fundamental to normal liver functionsand liver disease [37] Recently advanced progress has been



































PromotingInhibiting


miR-17

miR-18

miR-19

miR-20a

p27 p57


miR-1miR-92-1

miR-26a

miR-34amiR-195

miR-122

miR-7 miR-199

(a) Proliferation

miR-15amiR-16-1

miR-221


miR-224

Bim

miR-29miR-125

miR-122

Bmf Bcl-2 Bcl-w

PromotingInhibiting

(b) Apoptosis

PromotingInhibiting


miR-216

miR-221

miR-222

miR-519

miR-1

miR-34a

miR-198

miR-449

miR-141

miR-29amiR-126

miR-200

c-Met EMT VEGF

RhoA PTEN

(c) Metastasis










6 Conclusion





Acknowledgment


References




















































































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of


















































PromotingInhibiting


miR-17

miR-18

miR-19

miR-20a

p27 p57


miR-1miR-92-1

miR-26a

miR-34amiR-195

miR-122

miR-7 miR-199

(a) Proliferation

miR-15amiR-16-1

miR-221


miR-224

Bim

miR-29miR-125

miR-122

Bmf Bcl-2 Bcl-w

PromotingInhibiting

(b) Apoptosis

PromotingInhibiting


miR-216

miR-221

miR-222

miR-519

miR-1

miR-34a

miR-198

miR-449

miR-141

miR-29amiR-126

miR-200

c-Met EMT VEGF

RhoA PTEN

(c) Metastasis










6 Conclusion





Acknowledgment


References




















































































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of




















6 Conclusion





Acknowledgment


References




















































































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of






















































































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
















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