Review

Role of MicroRNAs in Prostate Cancer Pathogenesis You-Lin Wang,1 Shuai Wu,1 Bo Jiang,1 Fu-Fen Yin,2 Shuai-Shuai Zheng,1 Si-Chuan Hou1 Abstract Prostate cancer (PCa) remains the most commonly diagnosed malignant tumor in men, and is the second highest cause of cancer mortality after lung tumors in the United States. Accumulating research indicates that microRNAs (miRNAs) are increasingly being implicated in PCa. miRNAs are conserved small noncoding RNAs that control gene expression posttranscriptionally. Recent profiling research suggests that miRNAs are aberrantly expressed in PCa, and these have been implicated in the regulation of apoptosis, cell cycle, epithelial to mesenchymal transition, PCa stem cells, and androgen receptor pathway. All of these might provide the basis for new approaches for PCa. Here, we review current findings regarding miRNA research in PCa to provide a strong basis for future study aimed at promising contributions of miRNA in PCa. Clinical Genitourinary Cancer, Vol. -, No. -, --- ª 2015 Elsevier Inc. All rights reserved. Keywords: Androgen, Apoptosis, Cancer stem cells, Epithelial to mesenchymal transition, Metastasis

Introduction MicroRNAs (miRNAs or miRs) are a large class of endogenous tiny regulatory RNAs that extensively regulate gene expression. miRs function posttranscriptionally through imperfect base pairing with specific sequences in the 30 untranslated regions (UTRs) of target mRNAs leading to transcript degradation or translational inhibition.1 Studies have shown that miRs play key roles in cellular processes of differentiation, proliferation, apoptosis, and metabolic homeostasis. Depending on whether they specifically target oncogenes or tumor suppressor genes, miRNAs can function as either tumor suppressors or oncogenes. Prostate cancer (PCa) remains the most commonly diagnosed malignant tumor in men, and the second highest cause of cancer mortality after lung tumor in the United States.2 This is mainly because of the lack of definite diagnosis, curative therapies, and inherent complex heterogeneity of the tumors, thus making it difficult to determine which patient would respond to anticancer therapies. It is essential to better understand 1 Department of Urology, Qingdao Municipal Hospital, School of Medicine, Qingdao University, Qingdao, China 2 Department of Obstetrics and Gynecology, Affiliate Hospital of Qingdao University, Qingdao, China

the underlying molecular mechanisms and to develop more effective treatments. In this review we focus on novel findings in understanding the roles of miRs in the pathobiology of PCa, including miRs associated with the cell cycle, apoptosis, epithelial to mesenchymal transition (EMT) and mesenchymal to epithelial transition (MET) states, invasion and metastasis, PCa stem cell (PCSC), and androgen receptor (AR) pathway. We focus on literature published over the past 2 years (for earlier studies, see the reviews by Catto et al3 and Fang et al4).

Methods and Materials A comprehensive online search of peer-reviewed literature in PubMed (US National Library of Medicine, National Institute of Health; http://www.ncbi.nlm.nih.gov/pubmed/) was performed. References for this review were identified using the following terms: microRNA, prostate cancer, cell cycle, apoptosis, metastasis, EMT, cancer stem cells, androgen. All of the retrieved articles were reviewed and additional references were identified in the reference sections of the primary articles.

Submitted: Nov 26, 2014; Revised: Jan 9, 2015; Accepted: Jan 16, 2015

Biogenesis of miRs/Mechanisms of miRs Dysregulation

Addresses for correspondence to : Dr Si-Chuan Hou, PhD, MD or Shuai Wu, PhD, MD, Department of Urology, Qingdao Municipal Hospital, School of Medicine, Qingdao University, No. 5 Donghai Middle Road, Qingdao, Shandong Province 266071, China E-mail contact: [email protected], [email protected]

Most mammalian miRNA genes are first transcribed into long primary miRNAs (pri-miRNAs), which are 50 capped and 30 polyadenylated in the nucleus by RNA polymerase II or III.5 In the nucleus, pri-miRNA is processed by the DroshaeDiGeorge

1558-7673/$ - see frontmatter ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clgc.2015.01.003

Clinical Genitourinary Cancer Month 2015

-1

Role of MicroRNAs in Prostate Cancer Pathogenesis syndrome critical region gene 8 enzyme complex to generate a 60- to 90-nucleotide stem loop precursor miRNA (pre-miRNA).6 The pre-miRNA is transported to the cytoplasm via exportin 5, where it is cleaved by the type III RNase Dicer to generate mature (functional) 19- to 23-nucleotide double-stranded RNAs.7 One strand of the miRNA duplex can be incorporated into the RNA-induced silencing complex (RISC), and the complementary strand (miRNA*) degraded based on base-pairing stability at the duplex termini.8 MiRNA* has been originally considered to have no function and to be degraded; however, recent evidence suggests that it can be used as a functional strand and might play significant biological roles.9 RISC is composed of argonaute and associated proteins and controls gene expression via imperfect complementarity to the 30 UTR of target mRNAs leading to translational repression of protein expression or even degradation of the mRNA.10 MicroRNA expression can be modulated by transcription factors or abnormal maturation pathways. Many oncogenes or tumor suppressors can function as transcription factors. Several miRNA transcription factor connections have been discovered in PCa such as P53, E2F, and transforming growth factor-b (TGFb).11,12-14 miR-96 is an oncomir that is increased in PCa, and it is positively controlled by TGFb.14 TGFb regulates the expression of miR-96 through Sma- and Mad- related protein (Smad)-dependent transcription; and miR-96 targets serine/threonine-protein kinase 1 substrate 1 (AKT1S1) mRNA to promote bone metastasis.14 Fusion between the AR-regulated transmembrane protease, serine 2 (TMPRSS2) gene and erythroblast transformation-specific-related gene (ERG) are found in approximately 50% of PCa patients and are associated with poor prognosis.15 Recently, Kim et al identified that TMPRSS2:ERG directly represses transcription of miR-200c.16 The deregulated miRNA expression in cancer is also due to epigenetic changes, such as altered DNA methylation and histone modifications. Methylation of the CpG island of tumor suppressors results in their silencing and contributes to malignant transformation. Several reports have indeed shown that aberrant methylation can result in aberrant miRNA expression in PCa. DNA methylation is involved in silencing of genes that encode miR-205, miR-31, miR-145, miR-124, miR-200c/141, miR-23, and the miR-34 family.11,17-22 Furthermore, miR-152 downregulates DNA (cytosine-5)-methyltransferase 1 (DNMT1) in LNCaP, PC-3, and MDA-PCa-2b cells.23 DNMT1 small interfering RNA caused an increase of miR-152 expression, suggesting a reciprocal relationship between DNMT1 and miR-152. Increased DNMT1 and depletion of miR-152 are assumed to arise during the progression to advanced PCa.23

Role of miRs in Tumorigenesis and Progression Cell Cycle Deregulation

2

-

Deregulation of the cell cycle underlies the aberrant cell proliferation that characterizes cancer and loss of cell cycle checkpoint control promotes genetic instability. Abnormalities of the cell cycle are frequently observed in PCa, including reduced cyclindependent kinase (CDK) inhibitor p21 (Waf1/Cip1), p27 (Kip1) abundance, and increased abundance of cyclin D. miRNAs interact with E2F, cyclins, CDKs, and CDK inhibitors, providing the

Clinical Genitourinary Cancer Month 2015

potential to regulate cellular division and cell cycle progression.13,24,25 For example, miR-153 suppresses phosphatase and tensin homologue (PTEN) expression to activate AKT kinase and downregulate the transcriptional activity of Forkhead box protein O1 (FOXO1), leading to upregulation of cyclin D1 and downregulation of the CDK inhibitor p21.26 Although FOXO1 has been reported as a target of miR-96, Fendler et al did not observe an opposing effect or a rescue by miR-96 on cell cycle. One reason might be that the suppression of FOXO1 by miR-96 is not sufficient to induce cell cycle arrest.27 A recent report revealed that miR-888 reduced retinoblastoma-like 1 (RBL1), which belongs to the retinoblastoma family and functions to block first gap phase to synthetic phase cell cycle progression by binding and inhibiting the E2F transcription factors.28

Apoptosis Resistance Several miRs regulate the extrinsic cell death pathway. miR-24 directly targets Fas-associated factor 1, a Fas-binding proapoptotic protein, by binding to the amino acid coding sequence region of its mRNA in PCa.29 miR-133b involved in the regulation of cell death via death receptor-mediated apoptosis in HeLa and PC-3 cells.30 Forced expression of miR-133b sensitizes these cells to undergo tumor necrosis factor (TNF)ea-induced cell death and exacerbated proapoptotic responses to TNF-related apoptosis-inducing ligand or an activating antibody to Fas/CD95. Moreover, antiapoptotic protein Fas apoptosis inhibitory molecule was directly targeted by miR-133b.30 Some aberrantly expressed miRNAs contribute to the pathogenesis of human cancer by targeting B-cell lymphoma 2 (Bcl-2) family members. Members of the Bcl-2 family regulate apoptosis, and they are either proapoptotic (Bax, Bak, Bok, Bim, Bid, Bad, Bmf, Bik, BNIP3L, Noxa, Puma, and Hark) or antiapoptotic (Bcl2, Bcl-xL, Bcl-w, Mcl-1, and Al/Bfl-1).31 Bcl-2 family members could be targeted by some aberrantly expressed miRs, and thus regulate the apoptosis of cancer cells (Figure 1). Bcl-2 acts by directly interacting with Bcl-2-associated X protein (Bax) and Bcl-2 homologous antagonist killer (Bak) to prevent their oligomerization, thereby inhibiting mitochondrial apoptosis. Bcl-2 mRNA is directly targeted and inhibited by miR-34a,32 miR-34c,32 and miR-15a24 in PCa, which reduces proliferation, increases apoptosis, and sensitivity of multidrug-resistant PCa cells to chemotherapeutic agents.24,32 Bcl-xl, an antiapoptotic member of the Bcl-2 protein family, is expressed in a variety of cancer types, including PCa. miR-574-3p reduce Bcl-xl in PCa cells, and the expression of miR-574-3p could be upregulated by genistein.33 MiRNAs also possess a significant role in regulating chemotherapeutic agent-induced apoptosis in PCa cells. For instance, miR-205 and miR-31 are identified to target Bcl-w and E2F6, respectively, in PCa.34 Downregulation of both miRs result in resistance to apoptosis in highly malignant WPE1-NB26 cells. miR-205 also targets the antiapoptotic Bcl-2 gene.35 The reconstitution of PCa cells with miR-205 subsequently displayed a considerable increase in apoptosis on treatment with cisplatin and doxorubicin. In addition, miRNAs influence apoptosis through their regulation of tumor suppressors and oncogenes. miR-21 directly targets PTEN whose downregulation will release its inhibition on protein kinase B, resulting in significantly reduced apoptosis in PCa

You-Lin Wang et al Figure 1 A Diagram Showing miRNAs and Their Targets That Play a Role in the Regulation of Apoptosis

Abbreviations: DISC ¼ death inducing signaling complex; DR4/5 ¼ death receptor 4/5; FADD ¼ Fas-associating protein with a novel death domain; FAF1 ¼ FAS-associated factor 1; FasL ¼ Fas ligand; TRAIL ¼ TNF-related apoptosis-inducing ligand.

cells.36,37 Some other miRs have been recently found to function as tumor suppressors during the progression of PCa. miR-4723 is a novel miRNA that is downregulated in PCa.38 Arora and colleagues found that miR-4723 targets Abelson murine leukemia viral oncogene homolog 1 (Abl1) and Abl2 kinases, forced expression of miR-4723 induces apoptosis, and second gap phase to mitotic phase arrest in PCa cell lines.38

Epithelial to Mesenchymal Transition and MET States Epithelial to mesenchymal transition is a vital process for morphogenesis during embryonic development, but more recently it has also been implicated in the conversion of early stage tumors into invasive malignancies, the maintenance of stem cell properties, and therapy resistance (Figure 2).39,40 In PCa, cancer cells can undergo EMT to escape the primary tumor, invade surrounding tissues, and eventually colonize remote sites via blood or lymphatic routes to generate metastases. Metastatic cells can then revert through MET to reacquire epithelial characteristics similar to cells in the primary tumor.41,42 Integral to posttranscriptional regulation, miRNAs emerge as potent regulators of EMT and MET events through their ability to target the expression of key proteins that regulate these processes.43,44

Several miRNAs directly target EMT transcription factors in PCa (Figure 2). For example, miRs from the clustered miR-200 family members (miR-200a, miR-200b, miR-200c, miR-141, and miR-429) and miR-205 are downregulated in cancer cells during EMT. Loss of miR-200 family members and miR-205 in PCa can be mainly ascribed to the repressor activity of the E-cadherin repressors Zinc finger E-box-binding homeobox 1 (ZEB1) and ZEB2.45 Interestingly, the ZEB protein family also inhibits the expression of predominantly miR-200 family members indicating a mutual feedback mechanism that greatly promotes tumor development and tumorigenesis.46 The same double-negative feedback loop also exist between the miR-1/miR-200 family and Snail2,47 miR-145, and ZEB2 in PCa.48 MicroRNAs also affect the integrity of the epithelial architecture during EMT progression. miR-424 and miR-200 are commonly unregulated in an orthotopic mouse model of PCa metastasis. Overexpression of miR-424 plays a role in tumor cell plasticity and is sufficient to induce a MET in metastatic colonization of secondary sites.49 miR-143 and miR-145 are deregulated in PCa.50 Overexpression of these 2 miRs restore the expression of E-cadherin and simultaneously represses fibronectin expression in PC-3 cells,

Clinical Genitourinary Cancer Month 2015

-3

Role of MicroRNAs in Prostate Cancer Pathogenesis Figure 2 MicroRNAs Regulate Migration, Invasion, and Outgrowth at a Second Site by Regulating Epithelial to Mesenchymal Transition (EMT) and mesenchymal to epithelial transition States and Prostate Cancer (PCa) Stem Cells (PCSCs). (A) EMT Could Endow PCa Cells With Invasive and Metastatic Properties, Subsequently Cancer Cells Penetrate into Surrounding Tissues and Move at Distant Sites. EMT Phenotype Cells That Display Stem Cell Features Require the Capability of SelfRenewal, Which Is Important in the Growth of Micrometastases into Macroscopic Metastases. During This Process, MicroRNAs (miRs) Such as miR-320 and miR-409 Have Been Proposed to Regulate EMT and PCSCs. Numerous MicroRNAs (miRNAs) That Play a Pivotal Role in the Process of EMT and the Formation of Cancer Stem Cells Are Displayed in (B) and (C). (B) miRNAs Regulate Transcription Factors That Repress Epithelial Markers (E-Cadherin, a-Catenin and g-Catenin) and Activate Mesenchymal Markers (N-Cadherin, Vimentin, Fibronectin). (C) Examples of miRNAs Modulate the Pathway in the Formation of Stem Cells and Regulate Stem Cell- Makers

4

-

thus exerting a less invasive morphologic phenotype.51 Further studies have shown that miR-145 targets human enhancer of fiamentin 1 (HEF1), a positive regulator of EMT.52 HEF1 levels show a negative correlation with miR-145 in PCa and were higher in those with bone metastases, higher prostate-specific antigen levels, or higher Gleason grades.52 MicroRNAs in the delta-like 1 homologue-deiodinase, iodothyronine 3 (DLK1-DIO3) cluster are critical for embryonic development and EMT. miR-154*, miR-379, and miR-409 (located in the DLK1-DIO3 cluster) in circulating exosomes are upregulated in lung adenocarcinomas,53 breast cancer, and PCa.54,55 Lately, it is proposed that miR-154* and miR-379 levels are increased in PCa samples and miR-379 expression correlates with PCa patient progression-free survival. Inhibition of miR-154* resulted in decreased bone metastatic tumor growth and increased survival. miR-154* and miR-379 can promote EMT in PCa cells

Clinical Genitourinary Cancer Month 2015

in vitro. miR-154* mediates its effects by targeting stromal antigen 2 (STAG2) and functions as a tumor suppressor.56,57 Other miR154* target genes might be involved such as SMAD7, which inhibits the TGFb pathways involved in EMT.58 However, the sense strand of miR-154* is undetectable or decreased in PCa models and in PCa patients.59-61 With regard to miR-409, the same group has observed that miR-409-3p and -5p levels are increased in cancerassociated stroma fibroblasts in PCa tissue samples from patients with higher Gleason scores.62 In vitro studies have shown that miR-409-5p/-3p directly binds to the 30 UTR of Ras suppressor protein 1 and STAG2. Downregulation of miR-409 promotes tumor growth, EMT, and stemness of adjacent tumor epithelia in vivo.62 Moreover, this ectopic expression of miR-409 was released from extracellular vesicles and subject to uptake by surrounding epithelial cancer cells.62 These findings have particular translational importance, therefore miRs in the DLK1-DIO3

You-Lin Wang et al cluster can be attractive biomarkers and possible therapeutic targets for the treatment of PCa.

Invasion and Metastasis Metastatic development from a primary tumor to a metastatic lesion occurs through a multistep process—extracellular matrix remodeling, blood vessel recruitment, tumor cell entry and exit from circulation, and survival at a distant organ (Figure 2).63 Each step in this process represents a physiological barrier that must be overcome by the tumor cell for successful metastasis. Malignant cells overcome these barriers through the accumulation of genetic and epigenetic changes, including the deregulation of miRNA expression patterns. The involvement of miRs in the development of metastases was initially discovered by Ma and coworkers, who found that upregulation of miR-10b initiates breast cancer invasion and metastasis.64 Soon afterward, several miRs and their targets that express abnormally in PCa have been discovered to lead to the corresponding response in the invasion and metastasis of PCa. One well characterized example of a metastasis-regulatory miRNA is the miR-34 family. miR-34c is downregulated in PCa and inhibits malignant growth by repressing genes involved in some processes such as proliferation, antiapoptosis, stemness, and migration.65 Recent studies show that miR-34c regulates oncogene hepatocyte growth factor receptor (abbreviated MET#),66 a member of the receptor tyrosine kinase family which is known to promote motility and invasive capability of tumor cells.67 miR-34c and MET# might form a complex positive feedback loop by MET* / PI3K/AKT / mammalian target of rapamycin / p53 / miR-34 pathway.66,68,69 Another miRNA from the miR-34 family, miR-34a, is a well documented tumor suppressor that is decreased in PCa.70,71 miR-34a is shown to repress the expression of transcription factor 7 (TCF7). TCF7 is a Wnt signaling-related gene that is highly expressed in PCa tissues, and it has been implicated as a critical factor in bone metastasis.72 miR-34a also regulates baculoviral inhibitor of apoptosis repeatcontaining 5 (BIRC5/survivin) expression by targeting its 30 UTR, thus playing a crucial role in regulation of apoptosis in PCa.72 Additionally, the repression of TCF7 and BIRC5 by miR34 was detected in a Ras-activated PCa model.72 Upregulation of the miRs-221/222 has been reported in several types of tumors including PCa.25,73-75 As recently shown, miR-221 regulates cell growth, invasiveness, and apoptosis in PCa through coordinated repression of 2 genes—suppressor of cytokine signaling 3 (SOCS3) and interferon regulatory factor 2 (IRF2), 2 oncogenes that negatively regulate the Janus kinase/signal transducer and activator of transcription signaling pathway.76 Furthermore, miR221 downregulation might reduce the interferon-g responsiveness in primary PCa by upregulation of SOCS3 and IRF2, which can be used as a target for future therapies of high-risk PCa. Distinct lines of evidence reveal that miR-26a inhibits tumorigenesis and metastatic progression of human-tumor xenograft.77 miR-26a overexpression is accompanied by global upregulation of miRNAs, especially let-7.77 Based on this notion, Fu et al observed that miR-26a directly targets lin-28 homolog B and zinc finger CCHC domain containing 11 (ZCCHC11),77 which are critical repressors of the maturation of miRs, particularly let-7.78,79 In addition, ZCCHC11 was defined as an oncogene promoting tumor

growth and metastasis.77 Therefore, miR-26a in PCa inhibits tumorigenesis and metastasis through targeting oncogenes and enhancing miRNA biogenesis. MiR-940 is highly expressed in immortalized normal cells (PWR-1E and HPV-18C-1) compared with cancer cells (LNCaP, DU-145 and PC-3).80 It is also highly expressed in the normal tissues compared with its low to negligible expression in the tumors.80 Restoring the expression of miR-940 in PC-3 cells was able to inhibit migration, invasion, anchorage-independent growth, and EMT as a consequence of downregulation of its major target migration and invasion enhancer 1, a molecule involved in PCa migration and invasion.80 In addition, cells in the tumor microenvironment also display important regulatory roles during tumor progression. With respect to cancer-associated mesenchymal stem cells (MSCs), let-7 directly interacts with the 30 UTR of interleukin (IL)-6,81 downregulation of let-7 upregulates IL-6 expression. IL-6 has been reported to induce an invasive phenotype in nontumorigenic prostate epithelial cells through EMT.82 Upregulated IL-6 subsequently enhances adipogenesis and metastasis ability of cancer-associated MSCs.81

Prostate Cancer Stem Cells Emerging evidence has implicated that most solid tumors including PCa might arise from cancer stem cells (CSCs).83 The CSCs within the tumors might be involved in its proliferation, selfrenewal, survival, and differentiation,84 thus playing a critical role in the progression and recurrence of PCa to castration-resistant PCa and its subsequent metastasis. Several candidate populations of prostate stem/progenitor cells have been reported, including those expressing CD44, a2b1, or CD133.85,86 A variety of studies have shown the ectopic miRNA expression in CSC compared with normal tissues or non-CSC tumor tissues. This has extended to studies of PCSC. MicroRNA expression in PCa stem/progenitor cells was first profiled by Liu and colleagues.71 They identified miR-34a, let-7b, miR-141, and miR-106 to be commonly underexpressed in PCSCs, and miR-452 and miR-301 to be highly expressed.71,87 Recently, they found that miR-128 suppresses prostate CSC properties such as clonal, clonogenic, and tumorigenic activities by targeting the stem cell regulatory factors B cell-specific Moloney murine leukemia virus integration site 1, NANOG, and transforming growth factor b receptor (TGFBR) 1.88 Those factors vary inversely with miR-128 expression in PCa stem/progenitor cell populations. Moreover, B cell-specific Moloney murine leukemia virus integration site 1 acts as a direct and functionally relevant target of miR-128 in PCa cells.88 MiR-708 is downregulated in CD44þ subgroups of PCa cells, and restoration of its levels leads to decreased tumorigenicity.89 Further functional study revealed that miR-708 directly targets CD44 and the serine/threonine kinase AKT2. MiRNAs also regulate stem cell-like properties by regulating the Wnt pathway in PCa. Hsieh and coworkers found that the downregulation of miR-320 in PCa and decreased expression of miR-320 significantly increases the cancer stem cell-like properties such as tumorsphere formation, chemoresistance, and tumorigenic abilities.90 The global gene expression profiling of miR-320-overexpressing PCa cells

Clinical Genitourinary Cancer Month 2015

-5

Role of MicroRNAs in Prostate Cancer Pathogenesis Table 1 Roles of miRNAs in PCa miRNA Let-7a Let-7c miR-17-5p miR-34c miR-34a miR-31 miR-152 miR-200 Family miR-145 miR-23b miR-205 miR-1 miR-708 miR-320 miR-124 miR-135a MIR-26a miR-154 miR-135 miR-675 miR-185 miR-342 miR-494-3p miR-4723 miR-224 miR-940 miR-105 miR-130b miR-146 miR-218 miR-133b

miR-582-5p miR-154* (dlk1-dio3 cluster) miR-379 (dlk1-dio3 cluster) miR-409 (dlk1-dio3 cluster) miR-17 miR-3607 miR-888 miR-221

6

-

Controlled Biological Processes AR107 AR cell cycle, PCSC87,108 Cell cycle, AR104 invasion9 107

Targets

Property

Expression

Reason for Dysfunction

c-Myc107 EZH2108 p300/CBP104 TIMP3, P21, PTEN9 MET#66 TCF7, BIRC572 c-Myc70 AR, Notch-1 signaling109 AR,17 E2F6110 DNMT123

Tumor suppressor Tumor suppressor Tumor suppressor

Down Down Down

Transcriptional repression107 Transcriptional repression107 e

Tumor suppressor Tumor suppressor

Down Down

Tumor suppressor Tumor suppressor

Down Down

e Aberrant CpG methylation of miR-34a promoter109 Inhibited by EZH2110 DNMT123

Tumor suppressor

Down

Tumor suppressor Tumor suppressor

Down Down

TMPRSS2:ERG16 KLF5,111 AR137 ZEB248 e

Tumor suppressor

Down

Inhibited by EZH2110

Tumor Tumor Tumor Tumor Tumor Tumor Tumor

suppressor suppressor suppressor suppressor suppressor suppressor suppressor

Down Down Down Down Down Down Down

e e EZH2, CtBP1114 AR signaling100 e e

Tumor Tumor Tumor Tumor Tumor Tumor

suppressor suppressor suppressor suppressor suppressor suppressor

Down Down Down Down Down Down

AR signaling100 e e e e e

Tumor suppressor

Down

e

Tumor suppressor Tumor suppressor Tumor suppressor Tumor suppressor Tumor suppressor Tumor suppressor in PC-3 cells Oncomir in LNCaP cells Oncomir Oncomir

Down Down Down Down Down Up in LNCaP cells Down in PC-3 cells

e e e e e e

Up Up

e e

Cell cycle, PCSC87 Apoptosis and invasion,70,72 PCSC87 Cell cycle, apoptosis, AR17 Cell proliferation, migration, and invasion23 EMT,16,47,137 cell cycle, SNAI2/Slug47 invasion, and migration137 EMT48 ZEB248 Cell cycle, apoptosis, invasion, Src, Akt20 and migration, EMT20 Invasion112 MAPK and AR signaling,112 EZH2110 47 EMT SNAI2/Slug47 89 CD4489 PCSC 90 b-catenin90 EMT, PCSC 114 P4HA1114 Cell proliferation, invasion 100 Migration and invasion ROCK1, ROCK2100 77 Metastasis Lin28B, Zcchc1177 51 59 HMGA251, CCND259 EMT, Cell cycle, Invasion, and metastasis60 Invasion100 ROCK1, ROCK2100 128 Invasion TGFB1128 130 SREBP1, SREBP2130 Apoptosis and invasion 130 SREBP1, SREBP2130 Apoptosis and invasion 131 CXCR4131 Invasion Abl1, Abl238 Cell cycle, apoptosis, invasion38 Apoptosis and invasion132 TRIB1132 113 Invasion and migration TPD52113 80 EMT and invasion MIEN180 133 CDK6133 Invasion and migration 134 MMP2134 Invasion and migration RAC1135 Invasion and migration135 LASP1120 Invasion and migration120 FAIM30 Apoptosis30 Cell proliferation, RB1CC1117 cell cycle, apoptosis117 EFNB178 Cell proliferation78 118 STAG2, SMAD7118 EMT, metastasis EMT, metastasis118

FOXF2118

Oncomir

Up

e

EMT, PCSC62

RSU1, STAG2, NPRL2, RBL262 TIMP3, P21, PTEN9 LYN, SRC119

Oncomir

Up

e

Oncomir Oncomir

Up Up

e e

RBL1, SMAD428

Oncomir

Up

e

SOCS3, IRF276

Oncomir

Up

e

Cell cycle, invasion9 Cell cycle, apoptosis, and invasion119 Cell proliferation, cell cycle, migration28 Apoptosis, invasion76

Clinical Genitourinary Cancer Month 2015

You-Lin Wang et al Table 1 Continued miRNA

Controlled Biological Processes

miR-106b

Cell cycle, apoptosis121

miR-153 miR-32 miR-27a miR-141 miR-21

Cell proliferation, cell cycle26 Apoptosis, AR126 Cell cycle98 AR127 95 AR, invasion,129 EMT123

miR-20a miR-223-3p miR-296-3p miR-182 miR-96 miR-377

Invasion and migration136 Cell cycle, apoptosis, invasion138 Metastasis115 Cell cycle, apoptosis, invasion116 Metastasis14 EMT60

Targets

Property

Expression

Reason for Dysfunction

Caspase-7121 ZBTB4, Sp1, Sp3, Sp4122 PTEN, FOXO126 BTG2, PIK3IP1126 Prohibitin98 Shp127 p57Kip2,129 BTG2,123 RECK124

Oncomir

Up

e

Oncomir Oncomir Oncomir Oncomir Oncomir

Up Up Up Up Up

ABL2136 SEPT6138

Oncomir Oncomir

Up Up

e AR126 AR98 e AR signaling95 EF24 (a curcumin analogue)125 e e

ICAM-1115 NDRG1116

Oncomir Oncomir

Up Up

e e

AKT1S114 FZD460

Oncomir Oncomir

Up Up

TGFb14 e

Abbreviations: AR ¼ androgen receptor; EMT ¼ epithelial to mesenchymal transition; PCSC ¼ prostate cancer stem cell.

showed that miR-320 mainly regulates the Wnt/b-catenin pathway downstream target genes and subsequent decrease in CSC markers (CD44, Oct-4 and CD133).90 It has been indicated that fibronectin type III domain containing 3B (FNDC3B), which regulates cell motility, was identified as a target of miR-143.91 Subsequent work demonstrated upregulated miR-143 expression in PCSCs promoted PCa cell migration and invasion in vitro and promoted metastasis in vivo, by repressing FNDC3B expression.92 The ability of these miRNAs to target PCSCs suggests that they might have significant therapeutic potential.

Androgen Signal Pathway Androgen receptor is a ligand-dependent transcription factor and member of the hormone nuclear receptor superfamily. Many AR-regulated genes are closely related to prostate development and maintenance.93 AR-inducible miRs are regulated by androgens via an androgen response element (ARE) that is harbored in promoter regions. ARs act as a direct transcriptional regulator to miR-21 through the androgen-induced AR binding to the defined miR-21 promoter, miPPR-21.94 Forced expression of miR-21 further enhances androgen-dependent PCa growth in vivo and mediates castration resistance. Interestingly, upregulated miR-21 further significantly increased AR expression, forming a positive feedback loop in driving expression of the other.95 This signaling axis could further downregulate TGFBR2 expression and attenuate TGFb signaling in PCa.95 Early work by several independent groups demonstrated that miRs such as miR-19a, miR-148, and miR-27a are androgeninducible miRs that are regulated by androgens via an ARE.96-98 Genome-wide screening of androgen target genes have identified miR-125b-2 and miR-135a as androgen-inducible miRs.99,100 miR-125b contributes to the pathogenesis of PCa and acts as an oncogene.101 Overexpression of miR-125b stimulated the hormone-independent growth and downregulated the

expression of Bak1.101 However, a recent study conducted by Sun et al contrary to this,102 they indicated that the miR-99a/let7c/ 125b-2 cluster is transcriptionally repressed by androgenactivated AR. Similarly, AR transcriptionally activated the miR-135a2 gene by binding to an ARE in the promoter region.100 Roles of miR-135a in PCa cell invasion and migration were partly mediated by AR signaling.100 Moreover, some findings indicated that the negative correlation between AR and DNMT activity is one of the mechanisms that influence the methylation status of miRNA promoters, which in turn regulates their expression. AR levels are negatively correlated with the methylation-mediated transcriptional repression of miR-375 in human PCa cells.103 In AR-negative PCa cells, the low level of miR-375 partly caused by the hypermethylation of its promoter is related to high DNA methyltransferases activity, and in AR positive PCa, the opposite was observed.103 In contrast, miRs also modulate the androgen pathway. For instance, miR-17-5p targets p300/CBP-associated factor (PCAF), a coactivator of AR.104 Downregulated miR-17-5p negatively regulates the PCAF protein level, thereby regulating AR transcriptional activity and cell growth in cultured PCa cells. Recently, Yu et al demonstrated that phenethyl isothiocyanate restrains AR-regulated transcriptional activity and cell growth of PCa cells through miRe17-mediated suppression of PCAF.105 Other miRs such as miR-205 have been reported to directly target AR and are associated with adverse outcome of PCa patients.22,106

Conclusion MicroRNAs are important regulators of gene expression and have a wide variety of functions that enable them to interact with multiple pathways that modulate PCa progression. These miRs have been shown to act as oncomirs, often upregulated in PCa and facilitating tumor growth and progression, or acting as tumor

Clinical Genitourinary Cancer Month 2015

-7

Role of MicroRNAs in Prostate Cancer Pathogenesis suppressors, showing downregulation in PCa and inhibiting tumorigenesis (Table 1). Although miRs might have many useful clinical applications for patients with PCa, many additional studies are warranted to clarify their function and regulation during tumorigenesis and tumor progression.

Acknowledgments This work was supported by grants from the National Natural Science Foundation of China (No 81301968).

Disclosure The authors have stated that they have no conflicts of interest.

References 1. Baek D, Villén J, Shin C, Camargo FD, Gygi SP, Bartel DP. The impact of microRNAs on protein output. Nature 2008; 455:64-71. 2. Siegel R, Ma J, Zou Z, Jemal A. Cancer statistics, 2014. CA Cancer J Clin 2014; 64:9-29. 3. Catto JW, Alcaraz A, Bjartell AS, et al. MicroRNA in prostate, bladder, and kidney cancer: a systematic review. Eur Urol 2011; 59:671-81. 4. Fang YX, Gao WQ. Roles of microRNAs during prostatic tumorigenesis and tumor progression. Oncogene 2014; 33:135-47. 5. Cai X, Hagedorn CH, Cullen BR. Human microRNAs are processed from capped, polyadenylated transcripts that can also function as mRNAs. RNA 2004; 10:1957-66. 6. Gregory RI, Yan KP, Amuthan G, et al. The microprocessor complex mediates the genesis of microRNAs. Nature 2004; 432:235-40. 7. Hutvágner G, McLachlan J, Pasquinelli AE, Bálint É, Tuschl T, Zamore PD. A cellular function for the RNA-interference enzyme Dicer in the maturation of the let-7 small temporal RNA. Science 2001; 293:834-8. 8. Schwarz DS, Hutvágner G, Du T, Xu Z, Aronin N, Zamore PD. Asymmetry in the assembly of the RNAi enzyme complex. Cell 2003; 115:199-208. 9. Yang X, Du WW, Li H, et al. Both mature miR-17-5p and passenger strand miR-17-3p target TIMP3 and induce prostate tumor growth and invasion. Nucleic Acids Res 2013; 41:9688-704. 10. Peters L, Meister G. Argonaute proteins: mediators of RNA silencing. Mol Cell 2007; 26:611-23. 11. Suh SO, Chen Y, Zaman MS, et al. MicroRNA-145 is regulated by DNA methylation and p53 gene mutation in prostate cancer. Carcinogenesis 2011; 32:772-8. 12. Chang CJ, Chao CH, Xia W, et al. p53 regulates epithelial-mesenchymal transition and stem cell properties through modulating miRNAs. Nat Cell Biol 2011; 13:317-23. 13. Sylvestre Y, De Guire V, Querido E, et al. An E2F/miR-20a autoregulatory feedback loop. J Biol Chem 2007; 282:2135-43. 14. Siu MK, Tsai Y, Chang Y, et al. Transforming growth factor-beta promotes prostate bone metastasis through induction of microRNA-96 and activation of the mTOR pathway. Oncogene, Published online December 22, 2014; doi: 10. 1038/onc.2014.414. 15. Becker-Santos DD, Guo Y, Ghaffari M, et al. Integrin-linked kinase as a target for ERG-mediated invasive properties in prostate cancer models. Carcinogenesis 2012; 33:2558-67. 16. Kim J, Wu L, Zhao J, Jin H, Yu J. TMPRSS2eERG gene fusions induce prostate tumorigenesis by modulating microRNA miR-200c. Oncogene 2014; 33:5183-92. 17. Lin PC, Chiu YL, Banerjee S, et al. Epigenetic repression of miR-31 disrupts androgen receptor homeostasis and contributes to prostate cancer progression. Cancer Res 2013; 73:1232-44. 18. Lodygin D, Tarasov V, Epanchintsev A, et al. Inactivation of miR-34a by aberrant CpG methylation in multiple types of cancer. Cell Cycle 2008; 7:2591-600. 19. Vrba L, Jensen TJ, Garbe JC, et al. Role for DNA methylation in the regulation of miR-200c and miR-141 expression in normal and cancer cells. PLoS One 2010; 5:e8697. 20. Majid S, Dar AA, Saini S, et al. miR-23b represses proto-oncogene Src kinase and functions as methylation-silenced tumor suppressor with diagnostic and prognostic significance in prostate cancer. Cancer Res 2012; 72:6435-46. 21. Hulf T, Sibbritt T, Wiklund ED, et al. Epigenetic-induced repression of microRNA-205 is associated with MED1 activation and a poorer prognosis in localized prostate cancer. Oncogene 2013; 32:2891-9. 22. Shi X, Xue L, Ma A, et al. Tumor suppressive miR-124 targets androgen receptor and inhibits proliferation of prostate cancer cells. Oncogene 2013; 32:4130-8. 23. Theodore SC, Davis M, Zhao F, et al. MicroRNA profiling of novel African American and Caucasian prostate cancer cell lines reveals a reciprocal regulatory relationship of miR-152 and DNA methyltranferase 1. Oncotarget 2014; 5:3512-25.

8

-

Clinical Genitourinary Cancer Month 2015

24. Bonci D, Coppola V, Musumeci M, et al. The miR-15aemiR-16-1 cluster controls prostate cancer by targeting multiple oncogenic activities. Nat Med 2008; 14:1271-7. 25. Galardi S, Mercatelli N, Giorda E, et al. miR-221 and miR-222 expression affects the proliferation potential of human prostate carcinoma cell lines by targeting p27 Kip1. J Biol Chem 2007; 282:23716-24. 26. Wu Z, He B, He J, Mao X. Upregulation of miR-153 promotes cell proliferation via downregulation of the PTEN tumor suppressor gene in human prostate cancer. Prostate 2013; 73:596-604. 27. Fendler A, Jung M, Stephan C, Erbersdobler A, Jung K, Yousef GM. The antiapoptotic function of miR-96 in prostate cancer by inhibition of FOXO1. PLoS One 2013; 8:e80807. 28. Lewis H, Lance R, Troyer D, et al. miR-888 is an expressed prostatic secretionsderived microRNA that promotes prostate cell growth and migration. Cell Cycle 2014; 13:227-39. 29. Qin W, Shi Y, Zhao B, et al. miR-24 regulates apoptosis by targeting the open reading frame (ORF) region of FAF1 in cancer cells. PLoS One 2010; 5:e9429. 30. Patron JP, Fendler A, Bild M, et al. MiR-133b targets antiapoptotic genes and enhances death receptor-induced apoptosis. PLoS One 2012; 7:e35345. 31. Brumatti G, Salmanidis M, Ekert PG. Crossing paths: interactions between the cell death machinery and growth factor survival signals. Cell Mol Life Sci 2010; 67:1619-30. 32. Kojima K, Fujita Y, Nozawa Y, Deguchi T, Ito M. MiR-34a attenuates paclitaxel resistance of hormone-refractory prostate cancer PC3 cells through direct and indirect mechanisms. Prostate 2010; 70:1501-12. 33. Chiyomaru T, Yamamura S, Fukuhara S, et al. Genistein up-regulates tumor suppressor microRNA-574-3p in prostate cancer. PLoS One 2013; 8:e58929. 34. Bhatnagar N, Li X, Padi S, Zhang Q, Tang M, Guo B. Downregulation of miR-205 and miR-31 confers resistance to chemotherapy-induced apoptosis in prostate cancer cells. Cell Death Dis 2010; 1:e105. 35. Verdoodt B, Neid M, Vogt M, et al. MicroRNA-205, a novel regulator of the anti-apoptotic protein Bcl2, is downregulated in prostate cancer. Int J Oncol 2013; 43:307-14. 36. Yang CH, Yue J, Fan M, Pfeffer LM. IFN induces miR-21 through a signal transducer and activator of transcription 3edependent pathway as a suppressive negative feedback on IFN-induced apoptosis. Cancer Res 2010; 70: 8108-16. 37. Folini M, Gandellini P, Longoni N, et al. miR-21: an oncomir on strike in prostate cancer. Mol Cancer 2010; 9:12. 38. Arora S, Saini S, Fukuhara S, et al. MicroRNA-4723 inhibits prostate cancer growth through inactivation of the Abelson family of nonreceptor protein tyrosine kinases. PLoS One 2013; 8:e78023. 39. Thiery JP. Epithelial-mesenchymal transitions in tumour progression. Nat Rev Cancer 2002; 2:442-54. 40. Thiery JP, Acloque H, Huang RY, Nieto MA. Epithelialemesenchymal transitions in development and disease. Cell 2009; 139:871-90. 41. Thiery JP, Sleeman JP. Complex networks orchestrate epithelialemesenchymal transitions. Nat Rev Mol Cell Biol 2006; 7:131-42. 42. Yilmaz M, Christofori G. Mechanisms of motility in metastasizing cells. Mol Cancer Res 2010; 8:629-42. 43. Zhang J, Ma L. MicroRNA control of epithelialemesenchymal transition and metastasis. Cancer Metastasis Rev 2012; 31:653-62. 44. Xia H, Hui K. MicroRNAs involved in regulating epithelialemesenchymal transition and cancer stem cells as molecular targets for cancer therapeutics. Cancer Gene Ther 2012; 19:723-30. 45. Vandewalle C, Comijn J, De Craene B, et al. SIP1/ZEB2 induces EMT by repressing genes of different epithelial cellecell junctions. Nucleic Acids Res 2005; 33:6566-78. 46. Hill L, Browne G, Tulchinsky E. ZEB/miR-200 feedback loop: at the crossroads of signal transduction in cancer. Int J Cancer 2013; 132:745-54. 47. Liu Y, Yin J, Abou-Kheir W, et al. MiR-1 and miR-200 inhibit EMT via Slug-dependent and tumorigenesis via Slug-independent mechanisms. Oncogene 2012; 32:296-306. 48. Ren D, Wang M, Guo W, et al. Double-negative feedback loop between ZEB2 and miR-145 regulates epithelial-mesenchymal transition and stem cell properties in prostate cancer cells. Cell Tissue Res 2014; 358:763-78. 49. Banyard J, Chung I, Wilson AM, et al. Regulation of epithelial plasticity by miR-424 and miR-200 in a new prostate cancer metastasis model. Sci Rep 2013; 3:3151. 50. Schaefer A, Jung M, Mollenkopf HJ, et al. Diagnostic and prognostic implications of microRNA profiling in prostate carcinoma. Int J Cancer 2010; 126:1166-76. 51. Peng X, Guo W, Liu T, et al. Identification of miRs-143 and-145 that is associated with bone metastasis of prostate cancer and involved in the regulation of EMT. PLoS One 2011; 6:e20341. 52. Guo W, Ren D, Chen X, et al. HEF1 promotes epithelial mesenchymal transition and bone invasion in prostate cancer under the regulation of microRNA-145. J Cell Biochem 2013; 114:1606-15. 53. Cazzoli R, Buttitta F, Di Nicola M, et al. microRNAs derived from circulating exosomes as noninvasive biomarkers for screening and diagnosing lung cancer. J Thorac Oncol 2013; 8:1156-62. 54. Li S, Meng H, Zhou F, et al. MicroRNA-132 is frequently down-regulated in ductal carcinoma in situ (DCIS) of breast and acts as a tumor suppressor by inhibiting cell proliferation. Pathol Res Pract 2013; 209:179-83.

You-Lin Wang et al 55. Nguyen HC, Xie W, Yang M, et al. Expression differences of circulating microRNAs in metastatic castration resistant prostate cancer and low-risk, localized prostate cancer. Prostate 2013; 73:346-54. 56. Solomon DA, Kim T, Diaz-Martinez LA, et al. Mutational inactivation of STAG2 causes aneuploidy in human cancer. Science 2011; 333:1039-43. 57. Kim MS, Kim SS, Je EM, Yoo NJ, Lee SH. Mutational and expressional analyses of STAG2 gene in solid cancers. Neoplasma 2012; 59:524-9. 58. Lenferink AE, Cantin C, Nantel A, et al. Transcriptome profiling of a TGF-beta-induced epithelial-to-mesenchymal transition reveals extracellular clusterin as a target for therapeutic antibodies. Oncogene 2010; 29:831-44. 59. Zhu C, Shao P, Bao M, et al. miR-154 inhibits prostate cancer cell proliferation by targeting CCND2. Urol Oncol 2014; 32:31.e9-31.e16. 60. Formosa A, Markert EK, Lena AM, et al. MicroRNAs, miR-154, miR-299-5p, miR-376a, miR-376c, miR-377, miR-381, miR-487b, miR-485-3p, miR-495 and miR-654-3p, mapped to the 14q32.31 locus, regulate proliferation, apoptosis, migration and invasion in metastatic prostate cancer cells. Oncogene 2014; 33:5173-82. 61. Zhu C, Li J, Cheng G, et al. miR-154 inhibits EMT by targeting HMGA2 in prostate cancer cells. Mol Cell Biochem 2013; 379:69-75. 62. Josson S, Gururajan M, Sung SY, et al. Stromal fibroblast-derived miR-409 promotes epithelial-to-mesenchymal transition and prostate tumorigenesis. Oncogene, Published online July 28, 2014; doi: 10.1038/onc.2014.212. 63. Nguyen DX, Bos PD, Massagué J. Metastasis: from dissemination to organspecific colonization. Nat Rev Cancer 2009; 9:274-84. 64. Ma L, Teruya-Feldstein J, Weinberg RA. Tumour invasion and metastasis initiated by microRNA-10b in breast cancer. Nature 2007; 449:682-8. 65. Hagman Z, Larne O, Edsjo A, et al. miR-34c is downregulated in prostate cancer and exerts tumor suppressive functions. Int J Cancer 2010; 127:2768-76. 66. Hagman Z, Haflidadottir B, Ansari M, et al. The tumour suppressor miR-34c targets MET in prostate cancer cells. Br J Cancer 2013; 109:1271-8. 67. Trusolino L, Bertotti A, Comoglio PM. MET signalling: principles and functions in development, organ regeneration and cancer. Nat Rev Mol Cell Biol 2010; 11: 834-48. 68. Moumen A, Patane S, Porras A, Dono R, Maina F. Met acts on Mdm2 via mTOR to signal cell survival during development. Development 2007; 134:1443-51. 69. He L, He X, Lim LP, et al. A microRNA component of the p53 tumour suppressor network. Nature 2007; 447:1130-4. 70. Yamamura S, Saini S, Majid S, et al. MicroRNA-34a modulates c-Myc transcriptional complexes to suppress malignancy in human prostate cancer cells. PLoS One 2012; 7:e29722. 71. Liu C, Kelnar K, Liu B, et al. The microRNA miR-34a inhibits prostate cancer stem cells and metastasis by directly repressing CD44. Nat Med 2011; 17:211-5. 72. Chen WY, Liu SY, Chang YS, et al. MicroRNA-34a regulates WNT/TCF7 signaling and inhibits bone metastasis in Ras-activated prostate cancer. Oncotarget 2014; 6:441-57. 73. Sun T, Wang Q, Balk S, Brown M, Lee GS, Kantoff P. The role of microRNA-221 and microRNA-222 in androgen-independent prostate cancer cell lines. Cancer Res 2009; 69:3356-63. 74. Galardi S, Mercatelli N, Farace MG, Ciafrè SA. NF-kB and c-Jun induce the expression of the oncogenic miR-221 and miR-222 in prostate carcinoma and glioblastoma cells. Nucleic Acids Res 2011; 39:3892-902. 75. Chen Y, Zaman MS, Deng G, et al. MicroRNAs 221/222 and genisteinmediated regulation of ARHI tumor suppressor gene in prostate cancer. Cancer Prev Res (Phila) 2011; 4:76-86. 76. Kneitz B, Krebs M, Kalogirou C, et al. Survival in patients with high-risk prostate cancer is predicted by miR-221, which regulates proliferation, apoptosis, and invasion of prostate cancer cells by inhibiting IRF2 and SOCS3. Cancer Res 2014; 74:2591-603. 77. Fu X, Meng Z, Liang W, et al. miR-26a enhances miRNA biogenesis by targeting Lin28B and Zcchc11 to suppress tumor growth and metastasis. Oncogene 2014; 33:4296-306. 78. Viswanathan SR, Daley GQ. Lin28: a microRNA regulator with a macro role. Cell 2010; 140:445-9. 79. Thornton JE, Gregory RI. How does Lin28 let-7 control development and disease? Trends Cell Biol 2012; 22:474-82. 80. Rajendiran S, Parwani AV, Hare RJ, Dasgupta S, Roby RK, Vishwanatha JK. MicroRNA-940 suppresses prostate cancer migration and invasion by regulating MIEN1. Mol Cancer 2014; 13:250. 81. Sung SY, Liao CH, Wu HP, et al. Loss of Let-7 microRNA upregulates IL-6 in bone marrow-derived mesenchymal stem cells triggering a reactive stromal response to prostate cancer. PLoS One 2013; 8:e71637. 82. Rojas A, Liu G, Coleman I, et al. IL-6 promotes prostate tumorigenesis and progression through autocrine cross-activation of IGF-IR. Oncogene 2011; 30: 2345-55. 83. Visvader JE, Lindeman GJ. Cancer stem cells in solid tumours: accumulating evidence and unresolved questions. Nat Rev Cancer 2008; 8:755-68. 84. Clarke MF, Fuller M. Stem cells and cancer: two faces of eve. Cell 2006; 124:1111-5. 85. Collins AT, Habib FK, Maitland NJ, Neal DE. Identification and isolation of human prostate epithelial stem cells based on a2b1-integrin expression. J Cell Sci 2001; 114:3865-72. 86. Richardson GD, Robson CN, Lang SH, Neal DE, Maitland NJ, Collins AT. CD133, a novel marker for human prostatic epithelial stem cells. J Cell Sci 2004; 117:3539-45.

87. Liu C, Kelnar K, Vlassov AV, Brown D, Wang J, Tang DG. Distinct microRNA expression profiles in prostate cancer stem/progenitor cells and tumor-suppressive functions of let-7. Cancer Res 2012; 72:3393-404. 88. Jin M, Zhang T, Liu C, et al. miRNA-128 suppresses prostate cancer by inhibiting BMI-1 to inhibit tumor-initiating cells. Cancer Res 2014; 74:4183-95. 89. Saini S, Majid S, Shahryari V, et al. miRNA-708 control of CD44þ prostate cancer-initiating cells. Cancer Res 2012; 72:3618-30. 90. Hsieh IS, Chang KC, Tsai YT, et al. MicroRNA-320 suppresses the stem cell-like characteristics of prostate cancer cells by downregulating the Wnt/beta-catenin signaling pathway. Carcinogenesis 2013; 34:530-8. 91. Zhang X, Liu S, Hu T, Liu S, He Y, Sun S. Up-regulated microRNA-143 transcribed by nuclear factor kappa B enhances hepatocarcinoma metastasis by repressing fibronectin expression. Hepatology 2009; 50:490-9. 92. Fan X, Chen X, Deng W, Zhong G, Cai Q, Lin T. Up-regulated microRNA-143 in cancer stem cells differentiation promotes prostate cancer cells metastasis by modulating FNDC3B expression. BMC Cancer 2013; 13:61. 93. Balk SP. Androgen receptor as a target in androgen-independent prostate cancer. Urology 2002; 60:132-8. 94. Ribas J, Ni X, Haffner M, et al. miR-21: an androgen receptor-regulated microRNA that promotes hormone-dependent and hormone-independent prostate cancer growth. Cancer Res 2009; 69:7165-9. 95. Mishra S, Deng J, Gowda P, et al. Androgen receptor and microRNA-21 axis downregulates transforming growth factor beta receptor II (TGFBR2) expression in prostate cancer. Oncogene 2014; 33:4097-106. 96. Mo W, Zhang J, Li X, et al. Identification of novel AR-targeted microRNAs mediating androgen signalling through critical pathways to regulate cell viability in prostate cancer. PLoS One 2013; 8:e56592. 97. Murata T, Takayama K, Katayama S, et al. miR-148a is an androgen-responsive microRNA that promotes LNCaP prostate cell growth by repressing its target CAND1 expression. Prostate Cancer Prostatic Dis 2010; 13:356-61. 98. Fletcher CE, Dart DA, Sita-Lumsden A, Cheng H, Rennie PS, Bevan CL. Androgen-regulated processing of the oncomir MiR-27a, which targets Prohibitin in prostate cancer. Hum Mol Genet 2012; 21:3112-27. 99. Takayama K, Tsutsumi S, Katayama S, et al. Integration of cap analysis of gene expression and chromatin immunoprecipitation analysis on array reveals genomewide androgen receptor signaling in prostate cancer cells. Oncogene 2010; 30:619-30. 100. Kroiss A, Vincent S, Decaussin-Petrucci M, et al. Androgen-regulated microRNA-135a decreases prostate cancer cell migration and invasion through downregulating ROCK1 and ROCK2. Oncogene, Published online July 28, 2014; doi: 10.1038/onc.2014.222. 101. Shi XB, Xue L, Yang J, et al. An androgen-regulated miRNA suppresses Bak1 expression and induces androgen-independent growth of prostate cancer cells. Proc Natl Acad Sci U S A 2007; 104:19983-8. 102. Sun D, Layer R, Mueller A, et al. Regulation of several androgen-induced genes through the repression of the miR-99a/let-7c/miR-125b-2 miRNA cluster in prostate cancer cells. Oncogene 2014; 33:1448-57. 103. Chu M, Chang Y, Li P, Guo Y, Zhang K, Gao W. Androgen receptor is negatively correlated with the methylation-mediated transcriptional repression of miR-375 in human prostate cancer cells. Oncol Rep 2014; 31:34-40. 104. Gong AY, Eischeid AN, Xiao J, et al. miR-17-5p targets the p300/CBP-associated factor and modulates androgen receptor transcriptional activity in cultured prostate cancer cells. BMC Cancer 2012; 12:492. 105. Yu C, Gong AY, Chen D, Solelo Leon D, Young CY, Chen XM. Phenethyl isothiocyanate inhibits androgen receptor-regulated transcriptional activity in prostate cancer cells through suppressing PCAF. Mol Nutr Food Res 2013; 57:1825-33. 106. Hagman Z, Haflidadóttir B, Ceder J, et al. miR-205 negatively regulates the androgen receptor and is associated with adverse outcome of prostate cancer patients. Br J Cancer 2013; 108:1668-76. 107. Nadiminty N, Tummala R, Lou W, et al. MicroRNA let-7c suppresses androgen receptor expression and activity via regulation of Myc expression in prostate cancer cells. J Biol Chem 2012; 287:1527-37. 108. Kong D, Heath E, Chen W, et al. Loss of let-7 up-regulates EZH2 in prostate cancer consistent with the acquisition of cancer stem cell signatures that are attenuated by BR-DIM. PLoS One 2012; 7:e33729. 109. Kashat M, Azzouz L, Sarkar SH, Kong D, Li Y, Sarkar FH. Inactivation of AR and Notch-1 signaling by miR-34a attenuates prostate cancer aggressiveness. Am J Transl Res 2012; 4:432-42. 110. Zhang Q, Padi S, Tindall D, Guo B. Polycomb protein EZH2 suppresses apoptosis by silencing the proapoptotic miR-31. Cell Death Dis 2014; 5:e1486. 111. Zhang B, Zhang Z, Xia S, et al. KLF5 activates microRNA 200 transcription to maintain epithelial characteristics and prevent induced epithelial-mesenchymal transition in epithelial cells. Mol Cell Biol 2013; 33:4919-35. 112. Boll K, Reiche K, Kasack K, et al. MiR-130a, miR-203 and miR-205 jointly repress key oncogenic pathways and are downregulated in prostate carcinoma. Oncogene 2012; 32:277-85. 113. Goto Y, Nishikawa R, Kojima S, et al. Tumour-suppressive microRNA-224 inhibits cancer cell migration and invasion via targeting oncogenic TPD52 in prostate cancer. FEBS Lett 2014; 588:1973-82. 114. Chakravarthi BV, Pathi SS, Goswami MT, et al. The miR-124-prolyl hydroxylase P4HA1-MMP1 axis plays a critical role in prostate cancer progression. Oncotarget 2014; 5:6654-69. 115. Liu X, Chen Q, Yan J, et al. MiRNA-296-3p-ICAM-1 axis promotes metastasis of prostate cancer by possible enhancing survival of natural killer cell-resistant circulating tumour cells. Cell Death Dis 2013; 4:e928.

Clinical Genitourinary Cancer Month 2015

-9

Role of MicroRNAs in Prostate Cancer Pathogenesis 116. Liu R, Li J, Teng Z, Zhang Z, Xu Y. Overexpressed microRNA-182 promotes proliferation and invasion in prostate cancer PC-3 cells by downregulating N-myc downstream regulated gene 1 (NDRG1). PLoS One 2013; 8:e68982. 117. Li X, Wan X, Chen H, et al. Identification of miR-133b and RB1CC1 as independent predictors for biochemical recurrence and potential therapeutic targets for prostate cancer. Clin Cancer Res 2014; 20:2312-25. 118. Gururajan M, Josson S, Chu CY, et al. miR-154* and miR-379 in the DLK1-DIO3 microRNA mega-cluster regulate epithelial to mesenchymal transition and bone metastasis of prostate cancer. Clin Cancer Res 2014; 20: 6559-69. 119. Saini S, Majid S, Shahryari V, et al. Regulation of SRC kinases by microRNA-3607 located in a frequently deleted locus in prostate cancer. Mol Cancer Ther 2014; 13:1952-63. 120. Nishikawa R, Goto Y, Sakamoto S, et al. Tumor-suppressive microRNA-218 inhibits cancer cell migration and invasion via targeting of LASP1 in prostate cancer. Cancer Sci 2014; 105:802-11. 121. Hudson R, Yi M, Esposito D, et al. MicroRNA-106b-25 cluster expression is associated with early disease recurrence and targets caspase-7 and focal adhesion in human prostate cancer. Oncogene 2013; 32:4139-47. 122. Kim K, Chadalapaka G, Pathi SS, et al. Induction of the transcriptional repressor ZBTB4 in prostate cancer cells by drug-induced targeting of microRNA-17-92/ 106b-25 clusters. Mol Cancer Ther 2012; 11:1852-62. 123. Coppola V, Musumeci M, Patrizii M, et al. BTG2 loss and miR-21 upregulation contribute to prostate cell transformation by inducing luminal markers expression and epithelialemesenchymal transition. Oncogene 2013; 32:1843-53. 124. Reis ST, Pontes-Junior J, Antunes AA, et al. miR-21 may act as an oncomir by targeting RECK, a matrix metalloproteinase regulator, in prostate cancer. BMC Urol 2012; 12:14. 125. Yang CH, Yue J, Sims M, Pfeffer LM. The curcumin analog EF24 targets NF-kB and miRNA-21, and has potent anticancer activity in vitro and in vivo. PLoS One 2013; 8:e71130.

10

-

Clinical Genitourinary Cancer Month 2015

126. Jalava S, Urbanucci A, Latonen L, et al. Androgen-regulated miR-32 targets BTG2 and is overexpressed in castration-resistant prostate cancer. Oncogene 2012; 31:4460-71. 127. Xiao J, Gong AY, Eischeid AN, et al. miR-141 modulates androgen receptor transcriptional activity in human prostate cancer cells through targeting the small heterodimer partner protein. Prostate 2012; 72:1514-22. 128. Zhu M, Chen Q, Liu X, et al. lncRNA H19/miR-675 axis represses prostate cancer metastasis by targeting TGFBI. FEBS J 2014; 281:3766-75. 129. Mishra S, Lin CL, Huang TH, Bouamar H, Sun LZ. MicroRNA-21 inhibits p57Kip2 expression in prostate cancer. Mol Cancer 2014; 13:212. 130. Li X, Chen YT, Josson S, et al. MicroRNA-185 and 342 inhibit tumorigenicity and induce apoptosis through blockade of the SREBP metabolic pathway in prostate cancer cells. PLoS One 2013; 8:e70987. 131. Shen PF, Chen XQ, Liao YC, et al. MicroRNA-494-3p targets CXCR4 to suppress the proliferation, invasion, and migration of prostate cancer. Prostate 2014; 74:756-67. 132. Lin ZY, Huang YQ, Zhang YQ, et al. MicroRNA-224 inhibits progression of human prostate cancer by downregulating TRIB1. Int J Cancer 2014; 135:541-50. 133. Honeywell DR, Cabrita MA, Zhao H, Dimitroulakos J, Addison CL. miR-105 inhibits prostate tumour growth by suppressing CDK6 levels. PLoS One 2013; 8: e70515. 134. Chen Q, Zhao X, Zhang H, et al. MiR-130b suppresses prostate cancer metastasis through down-regulation of MMP2. Mol Carcinog, Published online August 23, 2014; doi: 10.1002/mc.22204. 135. Sun Q, Zhao X, Liu X, et al. miR-146a functions as a tumor suppressor in prostate cancer by targeting Rac1. Prostate 2014; 74:1613-21. 136. Qiang XF, Zhang ZW, Liu Q, et al. miR-20a promotes prostate cancer invasion and migration through targeting ABL2. J Cell Biochem 2014; 115:1269-76. 137. Williams LV, Veliceasa D, Vinokour E, Volpert OV. miR-200b inhibits prostate cancer EMT, growth and metastasis. PLoS One 2013; 8:e83991. 138. Wei Y, Yang J, Yi L, et al. MiR-223-3p targeting SEPT6 promotes the biological behavior of prostate cancer. Sci Rep 2014; 4:7546.