- Open Access
Enhancer of zeste homolog 2 (EZH2) in pediatric soft tissue sarcomas: first implications
BMC Medicine volume 9, Article number: 63 (2011)
Soft tissue sarcomas of childhood are a group of heterogeneous tumors thought to be derived from mesenchymal stem cells. Surgical resection is effective only in about 50% of cases and resistance to conventional chemotherapy is often responsible for treatment failure. Therefore, investigations on novel therapeutic targets are of fundamental importance. Deregulation of epigenetic mechanisms underlying chromatin modifications during stem cell differentiation has been suggested to contribute to soft tissue sarcoma pathogenesis. One of the main elements in this scenario is enhancer of zeste homolog 2 (EZH2), a methyltransferase belonging to the Polycomb group proteins. EZH2 catalyzes histone H3 methylation on gene promoters, thus repressing genes that induce stem cell differentiation to maintain an embryonic stem cell signature. EZH2 deregulated expression/function in soft tissue sarcomas has been recently reported. In this review, an overview of the recently reported functions of EZH2 in soft tissue sarcomas is given and the hypothesis that its expression might be involved in soft tissue sarcomagenesis is discussed. Finally, the therapeutic potential of epigenetic therapies modulating EZH2-mediated gene repression is considered.
Soft tissue sarcomas: a clinical challenge
Soft tissue sarcomas (STSs) are a group of heterogeneous malignant neoplasms thought to arise from molecular lesions occurring during the differentiation of mesenchymal stem cells (MSCs) . STSs account for less than 1% of all adult tumors and for about 15% of all pediatric ones, with an estimated 10,520 new cases in the US in 2010 [2, 3]. A series of chromosomal translocations have been identified as hallmarks of most STSs, such as t(X;18)(p11.2;q11.2) in synovial sarcoma, t(11;22)(q24;q12) in Ewing's sarcoma, t(2;13)(q35;q14) and t(1;13)(p36;q14) in alveolar rhabdomyosarcoma (RMS). These chromosomal rearrangements result in oncogenic fusion proteins that play direct roles in altering gene expression pattern in STS, promoting tumor aggressiveness. Because of their infiltrating behavior, only 50% of STSs are suitable for radical surgical resection. Moreover, a fraction of STSs are resistant to chemotherapeutic agents, especially the metastatic forms . Doxorubicin, the drug used in standard single-agent chemotherapy protocols for the treatment of metastatic STS, results in only 20% to 25% response rates. Even the combination of doxorubicin with other agents, such as ifosfamide, has not dramatically improved the overall 5-year survival rate, which is no higher than 50% to 60% . Nevertheless, chemotherapy represents the only viable strategy for palliation of symptoms in patients with metastatic disease, improving their quality of life . New promising biological drugs, such as monoclonal antibodies to insulin-like growth factor receptor (IGFR), inhibitors of multityrosine kinases, and mammalian target of rapamycin (mTOR), have been introduced in STS clinical trials (Table 1) . However, disease stabilization is still not seen in many patients, especially those affected by peculiar histological variants or showing poor-risk factors; it is reasonable to hypothesize that a combination of cytotoxic chemotherapy with targeted agents may be more appropriate to improve outcome in STS patients. A novel class of therapeutic targets is represented by epigenetic regulators, such as DNA methyltransferases (DNMTs), histone acetylases (HATs), histone deacetylases (HDACs), and histone methyltransferases (HMTs). Physiologically, all these enzymes work in concert for regulating gene expression by modifying the state of chromatin without altering DNA gene sequences in order to obtain a proper tissue determination. Increasing evidence demonstrates that they play key roles in human tumorigenesis, often being deregulated in terms of expression and/or activity and leading to silencing of essential regulators of cell proliferation and differentiation. Indeed, from comparative analyses, it appears that cancer genomes show different patterns of epigenetic modifications as compared to normal cells. Using inhibitory agents of all of these enzymes, it is possible to obtain pharmacological reversion of the tumor-specific gene expression profile, as well as reactivation of abnormally silenced tumor-suppressor genes in cancer cells . Among these regulatory players, the histone methyltransferase enhancer of zeste homolog 2 (EZH2) is considered one of the most appealing epigenetic targets for therapy in human cancer .
The Polycomb group protein EZH2 in STS
EZH2 is one of the Polycomb group (PcG) proteins, which repress expression of developmentally regulated genes that induce tissue differentiation, such as homeotic genes. PcG proteins help maintaining the undifferentiated, multipotent phenotype of the embryonic stem cell compartment [7–11]. In vertebrates, PcG proteins form two different groups of multiprotein Polycomb repressor complexes (PRCs), PRC1 and PRC2/3. EZH2 is the catalytic unit of the PRC2/3 complex, the part involved in the initiation of gene repression. EZH2 methylates lysine 27 of histone H3, thus generating the H3K27-trimethylated epigenetic mark that is recognized by the PRC1 complex for further, long-term chromatin modifications (Figure 1a) . EZH2 is promptly downregulated during progenitor cell differentiation, becoming undetectable in adult specialized cells and tissues (Figure 1b) . Conversely, EZH2 is abnormally overexpressed in a wide range of tumors as compared with corresponding normal tissues, its level of expression being correlated with cancer aggressiveness [7, 13, 14]. Moreover, the abundance of EZH2 molecules induces the formation of more repressor complexes and, by altering the balance between different PcG components, may lead to the formation of tumor-specific PRC complexes that show differential substrate specificities . As a result, not only the general level of repression but also the specificity of repressed genes is changed. EZH2 has recently been found aberrantly expressed in aggressive and poorly differentiated breast and prostate carcinomas [13, 14], as well as in STS [16, 17]. EZH2 aberrant overexpression may be one of the molecular lesions occurring in differentiating mesenchymal stem cells (MSCs), which are thought to be the cells of origin of STS . It has been proposed that the presence of EZH2 in tumors with embryonal features and stem-cell phenotype, such as STS, may explain their undifferentiated and immature character. In view of these data, EZH2 appears to be an attractive target for investigation in STS.
EZH2 in RMS
RMSs are a heterogeneous group of STSs characterized by features of skeletal muscle tissue and thought to be caused by abnormalities occurring during the course of myogenesis [18, 19]. It prevalently affects pediatric patients and accounts for almost 50% of all STSs . Classically, RMSs are histologically subdivided in two subtypes: the alveolar and embryonal forms. More recently, it has been reported that a diagnosis of alveolar RMS can be made only in the presence of two specific molecular aberrations, namely t(2;13)(q35;q14) and/or t(1;13)(p36;q14) chromosomal translocations resulting in PAX3-FKHR and the rarer PAX7-FKHR oncogenic fusion proteins, respectively . These lesions have been found in about 20% of all RMSs and in about 70% of the RMSs with an alveolar histology [21, 22]. True alveolar RMSs are often metastatic at diagnosis, show unresponsiveness to conventional therapy and have poor prognosis, the long-term survival rate being < 25% [23, 24]. Fusion-negative RMSs include tumors with embryonal histology and the remaining part of RMSs with an alveolar histology . Evidence for aberrant overexpression of EZH2 in RMS samples has been reported by Wang and colleagues  and by our studies in RMS cell lines and primary samples . We have recently confirmed this finding in a large cohort of RMS specimens, documenting that overexpression of EZH2 is a hallmark of RMS, independently of the histological subtype . It remains to be determined whether the level of EZH2 expression correlates with the presence of fusion proteins typical of the alveolar subtype. These results are consistent with the observation that in a physiological context EZH2 inhibits muscle differentiation of normal myoblasts by silencing muscle-specific genes . Among these genes are those encoding for promyogenic microRNAs, such as miR-214 and miR-29. These belong to a class of small RNAs that inhibits the translation of selected mRNAs thus preventing their protein expression [25, 28]. Mir-26a is another microRNA acting to post-transcriptionally repress EZH2 in normal myoblasts undergoing differentiation (Figure 2a left panel) . During differentiation, miR-29 is induced and targets the PcG transcription factor yin yang 1 (YY1) mRNA promoting its degradation (Figure 2a left panel). In the absence of a myogenic stimulus and in RMS cells, EZH2 is recruited together with HDAC1 by YY1 to repress transcription of both myofibrillary genes [27, 30] and miR-29 (Figure 2a right panel) . Similarly, miR-214 is directly repressed by EZH2 in undifferentiated committed myoblasts and, in turn, it is able to bring about negative feedback on EZH2 during myogenesis by targeting its transcript . A role for miR-26a and miR-29 in RMS pathogenesis was confirmed by recent studies [16, 25]. We found that miR-26a is aberrantly downregulated in RMS cell lines and primary tumors as compared to non-tumor counterparts, and that miR-26a loss of expression is paralleled by an overexpression of EZH2 . Similarly, miR-29 levels are reduced in tumor samples as compared with control muscle tissues. This finding can be interpreted considering that overexpressed EZH2 and YY1 are capable to repress miR-29 transcription in RMS cells (Figure 2a) . In agreement with the above observations, it has been found that mi-R29 ectopic expression promotes RMS cell-cycle arrest, myogenic cell differentiation and tumor growth inhibition in a xenograft model . Reduction of miR-29 levels had been previously reported in a small cohort of alveolar RMS . Altogether, these findings provide evidence for a key role of EZH2-mediated epigenetic changes in RMS pathogenesis, which involve also mutual interactions with microRNAs.
EZH2 in synovial sarcoma
Synovial sarcoma is a malignant cancer that affects prevalently young patients and represents almost 10% of all STSs . It is characterized by the typical translocation t(X;18)(p11;q11) that generates the fusion between the synovial sarcoma translocation, chromosome 18 (SS18 or SYT) gene on chromosome 18 and either synovial sarcoma, X breakpoint 1, 2 or 4 (SSX1, SSX2 or SSX4) genes on the X chromosome . Previously reported data showed that chimerical proteins SYT-SSX might disrupt gene expression mechanisms by functionally interacting with PcG proteins in synovial cells . In particular, SYT-SSX2 fusion protein induces downstream target-gene deregulation through epigenetic mechanisms . Recently, EZH2 has been found to mediate the effects of SYT-SSX activity. Specifically, SYT-SSX2 represses the expression of the tumor suppressor gene early growth response 1 (EGR1), a regulator of cell cycle, engaging EZH2 on the EGR1 promoter in synovial sarcoma cells (Figure 2b). EGR1 repression has been found to be associated with H3K27 trimethylation, and EZH2 and the PRC1 component BMI1 have been shown to directly bind its promoter, thus supporting the existence of a novel epigenetic mechanism of oncogenesis in synovial sarcoma . This finding illustrates how a genetic lesion that generates an oncogenic trascriptional regulator might exploit EZH2 and other epigenetic regulators to sustain tumorigenesis.
EZH2 in Ewing's sarcoma
Ewing's sarcoma is an embryonal malignancy characterized by the t(11;22)(q24;q12) translocation which generates chimerical Ewing sarcoma (EWS)/ETS fusion transcription factors. One of the most common fusion protein found in patients affected by this tumor is EWS/Friend leukemia integration 1 transcription factor (FLI1) . EZH2 is expressed at high levels in Ewing's tumors . Studying the influence of EZH2 downregulation on gene expression, Richter and colleagues found that EZH2 is responsible for the undifferentiated phenotype of Ewing's sarcoma by maintaining a stemness gene expression signature, inhibiting differentiation . Strikingly, EWS/FLI1 has been found to induce the expression of EZH2 by direct binding to its promoter in both Ewing's sarcoma cell lines and human MSCs (Figure 2c) . EWS/FLI1-dependent activation of EZH2 seems to be specific, because the other components of the PRC2/3 complex are not affected . Notably, human MSCs seem to represent a permissive environment for the expression of EWS/FLI1, which induces features in these cells that recapitulate Ewing's sarcoma biology. This observation may implicate EZH2 as a coinitiator of Ewing's sarcoma . Data from these studies offer an example of how a translocation-derived fusion product takes advantage of EZH2 recruiting this methyltransferase to drive tumor progression at the expenses of differentiation.
Concluding remarks and future perspectives
Pediatric STSs, especially those metastatic at diagnosis, are highly aggressive tumors for which there is still an unmet medical need of more effective and less toxic therapeutic approaches. The role of the epigenetic regulator EZH2 in maintaining the embryonal cell phenotype of STS, its overexpression in these cancers and its functional interaction with many fusion proteins typical of STS, suggest that EZH2 may represent both a potential marker of undifferentiated precancerous cells and a reasonable candidate therapeutic target in STS. Increasing attention is focusing on epigenetic therapies that have provided promising results in clinical trials for some human tumors [40–42]. The clinical effectiveness of epigenetic therapies in human malignancies has been recently proved by the observation that, in a randomized phase III trial, the DNA hypomethylating agent azacytidine prolonged overall survival of myelodysplastic syndrome (MDS) patients compared to other standard therapies . The potential efficacy of epigenetic therapy in STS is supported by preclinical studies employing HDAC inhibitors [36, 44–46]. Many studies on cell culture and animal models indicate that diverse epigenetic processes synergize to control gene expression. Hence, different kinds of epigenetic drugs, such as DNA-demethylating agents and HDAC inhibitors, have been included in combination treatment protocols [40, 47]. It is noteworthy that, in Ewing's sarcoma cells, HDAC inhibitor treatment in vitro induces downregulation of EZH2 , as more recently confirmed in glioma , gallbladder carcinoma  and acute myeloid leukemia . Consistently, in preclinical models of different cancers, the antitumor effect of EZH2 inhibition, obtained through the methyltransferase inhibitor 3'-deazanoplanocin (DZNep), is enhanced by addition of HDAC inhibitors [51–53]. DZNep has been shown to act by causing depletion of PRC2 subunits with subsequent reactivation of PRC2-silenced genes [54, 55]. In addition, it has been shown that the repressive function of EZH2 on gene expression is strengthened by the role of DNMTs, with which EZH2 physically interacts regulating their activity . In this view, additional usage of DNMTs inhibitors in protocols targeting EZH2 might improve response in some tumor contexts. In turn, since HMTs are also active in non-proliferating cells, the inclusion of EZH2 inhibitors in combination regimens may overcome the ineffectiveness of DNMTs inhibitors in quiescent cells. On the other hand, it must be noted that, due to the complexity of molecular crosstalk involved in epigenetic control, the use of epigenetic drugs affecting a variety of molecular networks entails the risk of unforeseeable effects. For instance, despite their antiproliferative effects in vitro, treatments employing either HDACs or DNA methylation inhibitors have been recently reported to increase in vivo the invasive capabilities of RMS cells through upregulation of the prometastatic gene Ezrin . Major questions remain open on the in vivo mechanism(s) of action of epigenetic drugs. Indeed, the clinical response to azacytidine in terms of prolongation of survival in MDS patients does not appear to be directly correlated with methylation of specific tumor suppressor genes, though methylation status has been shown to correlate with poor survival . Even if future preclinical studies will better clarify the mechanisms of action of these drugs on gene expression, preclinical findings will need to be validated in humans .
Despite these unresolved questions, epigenetic therapy is a promising approach for targeted anticancer therapies in pediatric STS. Available evidence suggests that targeting the methyltransferase EZH2 may be potentially able to restore physiological patterns of gene expression in pediatric STS. In the future, modulation of EZH2 activity may provide a new line of intervention that could be combined with epigenetic drugs acting on other molecular targets and/or conventional cytotoxic agents to treat these aggressive pediatric tumors.
Siddiqi S, Mills J, Matushansky I: Epigenetic remodeling of chromatin architecture: exploring tumor differentiation therapies in mesenchymal stem cells and sarcomas. Curr Stem Cell Res Ther. 2010, 5: 63-73. 10.2174/157488810790442859.
Jemal A, Siegel R, Xu J, Ward E: Cancer statistics, 2010. CA Cancer J Clin. 2010, 60: 277-300. 10.3322/caac.20073.
Vincenzi B, Frezza AM, Santini D, Tonini G: New therapies in soft tissue sarcoma. Expert Opin Emerg Drugs. 2010, 15: 237-248. 10.1517/14728211003592108.
Ganjoo KN: New developments in targeted therapy for soft tissue sarcoma. Curr Oncol Rep. 2010, 12: 261-265. 10.1007/s11912-010-0107-2.
Krikelis D, Judson I: Role of chemotherapy in the management of soft tissue sarcomas. Expert Rev Anticancer Ther. 2010, 10: 249-260. 10.1586/era.09.176.
Yoo CB, Jones PA: Epigenetic therapy of cancer: past, present and future. Nat Rev Drug Discov. 2006, 5: 37-50. 10.1038/nrd1930.
Simon JA, Lange CA: Roles of the EZH2 histone methyltransferase in cancer epigenetics. Mutat Res. 2008, 647: 21-29.
Sparmann A, van Lohuizen M: Polycomb silencers control cell fate, development and cancer. Nat Rev Cancer. 2006, 6: 846-856. 10.1038/nrc1991.
Ringrose L, Paro R: Epigenetic regulation of cellular memory by the Polycomb and Trithorax group proteins. Annu Rev Genet. 2004, 38: 413-443. 10.1146/annurev.genet.38.072902.091907.
Rajasekhar VK, Begemann M: Concise review: roles of polycomb group proteins in development and disease: a stem cell perspective. Stem Cells. 2007, 25: 2498-2510. 10.1634/stemcells.2006-0608.
Schuettengruber B, Chourrout D, Vervoort M, Leblanc B, Cavalli G: Genome regulation by polycomb and trithorax proteins. Cell. 2007, 128: 735-745. 10.1016/j.cell.2007.02.009.
Laible G, Wolf A, Dorn R, Reuter G, Nislow C, Lebersorger A, Popkin D, Pillus L, Jenuwein T: Mammalian homologues of the Polycomb-group gene Enhancer of zeste mediate gene silencing in Drosophila heterochromatin and at S. cerevisiae telomeres. Embo J. 1997, 16: 3219-3232. 10.1093/emboj/16.11.3219.
Kleer CG, Cao Q, Varambally S, Shen R, Ota I, Tomlins SA, Ghosh D, Sewalt RG, Otte AP, Hayes DF, Sabel MS, Livant D, Weiss SJ, Rubin MA, Chinnaiyan AM: EZH2 is a marker of aggressive breast cancer and promotes neoplastic transformation of breast epithelial cells. Proc Natl Acad Sci USA. 2003, 100: 11606-11611. 10.1073/pnas.1933744100.
Varambally S, Dhanasekaran SM, Zhou M, Barrette TR, Kumar-Sinha C, Sanda MG, Ghosh D, Pienta KJ, Sewalt RG, Otte AP, Rubin MA, Chinnaiyan AM: The polycomb group protein EZH2 is involved in progression of prostate cancer. Nature. 2002, 419: 624-629. 10.1038/nature01075.
Kuzmichev A, Margueron R, Vaquero A, Preissner TS, Scher M, Kirmizis A, Ouyang X, Brockdorff N, Abate-Shen C, Farnham P, Reinberg D: Composition and histone substrates of polycomb repressive group complexes change during cellular differentiation. Proc Natl Acad Sci USA. 2005, 102: 1859-1864. 10.1073/pnas.0409875102.
Ciarapica R, Russo G, Verginelli F, Raimondi L, Donfrancesco A, Rota R, Giordano A: Deregulated expression of miR-26a and Ezh2 in rhabdomyosarcoma. Cell Cycle. 2009, 8: 172-175. 10.4161/cc.8.1.7292.
Richter GH, Plehm S, Fasan A, Rössler S, Unland R, Bennani-Baiti IM, Hotfilder M, Löwel D, von Luettichau I, Mossbrugger I, Quintanilla-Martinez L, Kovar H, Staege MS, Müller-Tidow C, Burdach S: EZH2 is a mediator of EWS/FLI1 driven tumor growth and metastasis blocking endothelial and neuro-ectodermal differentiation. Proc Natl Acad Sci USA. 2009, 106: 5324-5329. 10.1073/pnas.0810759106.
De Giovanni C, Landuzzi L, Nicoletti G, Lollini PL, Nanni P: Molecular and cellular biology of rhabdomyosarcoma. Future Oncol. 2009, 5: 1449-1475. 10.2217/fon.09.97.
Charytonowicz E, Cordon-Cardo C, Matushansky I, Ziman M: Alveolar rhabdomyosarcoma: is the cell of origin a mesenchymal stem cell?. Cancer Lett. 2009, 279: 126-136. 10.1016/j.canlet.2008.09.039.
Merlino G, Helman LJ: Rhabdomyosarcoma--working out the pathways. Oncogene. 1999, 18: 5340-5348. 10.1038/sj.onc.1203038.
Williamson D, Missiaglia E, de Reyniès A, Pierron G, Thuille B, Palenzuela G, Thway K, Orbach D, Laé M, Fréneaux P, Pritchard-Jones K, Oberlin O, Shipley J, Delattre O: Fusion gene-negative alveolar rhabdomyosarcoma is clinically and molecularly indistinguishable from embryonal rhabdomyosarcoma. J Clin Oncol. 2010, 28: 2151-2158. 10.1200/JCO.2009.26.3814.
Davicioni E, Anderson JR, Buckley JD, Meyer WH, Triche TJ: Gene expression profiling for survival prediction in pediatric rhabdomyosarcomas: a report from the children's oncology group. J Clin Oncol. 2010, 28: 1240-1246. 10.1200/JCO.2008.21.1268.
Davicioni E, Finckenstein FG, Shahbazian V, Buckley JD, Triche TJ, Anderson MJ: Identification of a PAX-FKHR gene expression signature that defines molecular classes and determines the prognosis of alveolar rhabdomyosarcomas. Cancer Res. 2006, 66: 6936-6946. 10.1158/0008-5472.CAN-05-4578.
Lae M, Ahn EH, Mercado GE, Chuai S, Edgar M, Pawel BR, Olshen A, Barr FG, Ladanyi M: Global gene expression profiling of PAX-FKHR fusion-positive alveolar and PAX-FKHR fusion-negative embryonal rhabdomyosarcomas. J Pathol. 2007, 212: 143-151. 10.1002/path.2170.
Wang H, Garzon R, Sun H, Ladner KJ, Singh R, Dahlman J, Cheng A, Hall BM, Qualman SJ, Chandler DS, Croce CM, Guttridge DC: NF-kappaB-YY1-miR-29 regulatory circuitry in skeletal myogenesis and rhabdomyosarcoma. Cancer Cell. 2008, 14: 369-381. 10.1016/j.ccr.2008.10.006.
Ciarapica R, Pezzullo M, Verginelli F, Boldrini R, Sio LD, Stifani S, Giordano A, Rota R: Abstract #3417: Ezh2 is up-regulated and correlates with Ki67 and CD31 expression in human pediatric rhabdomyosarcoma. AACR Meeting Abstracts. 2010, American Association for Cancer Reasearch, Philadelphia, PA
Caretti G, Di Padova M, Micales B, Lyons GE, Sartorelli V: The Polycomb Ezh2 methyltransferase regulates muscle gene expression and skeletal muscle differentiation. Genes Dev. 2004, 18: 2627-2638. 10.1101/gad.1241904.
Juan AH, Kumar RM, Marx JG, Young RA, Sartorelli V: Mir-214-dependent regulation of the polycomb protein Ezh2 in skeletal muscle and embryonic stem cells. Mol Cell. 2009, 36: 61-74. 10.1016/j.molcel.2009.08.008.
Wong CF, Tellam RL: MicroRNA-26a targets the histone methyltransferase Enhancer of Zeste homolog 2 during myogenesis. J Biol Chem. 2008, 283: 9836-9843. 10.1074/jbc.M709614200.
Wang H, Hertlein E, Bakkar N, Sun H, Acharyya S, Wang J, Carathers M, Davuluri R, Guttridge DC: NF-kappaB regulation of YY1 inhibits skeletal myogenesis through transcriptional silencing of myofibrillar genes. Mol Cell Biol. 2007, 27: 4374-4387. 10.1128/MCB.02020-06.
Subramanian S, Lui WO, Lee CH, Espinosa I, Nielsen TO, Heinrich MC, Corless CL, Fire AZ, van de Rijn M: MicroRNA expression signature of human sarcomas. Oncogene. 2008, 27: 2015-2026. 10.1038/sj.onc.1210836.
Okcu MF, Despa S, Choroszy M, Berrak SG, Cangir A, Jaffe N, Raney RB: Synovial sarcoma in children and adolescents: thirty three years of experience with multimodal therapy. Med Pediatr Oncol. 2001, 37: 90-96. 10.1002/mpo.1175.
Jain S, Xu R, Prieto VG, Lee P: Molecular classification of soft tissue sarcomas and its clinical applications. Int J Clin Exp Pathol. 2010, 3: 416-428.
Soulez M, Saurin AJ, Freemont PS, Knight JC: SSX and the synovial-sarcoma-specific chimaeric protein SYT-SSX co-localize with the human Polycomb group complex. Oncogene. 1999, 18: 2739-2746. 10.1038/sj.onc.1202613.
de Bruijn DR, Allander SV, van Dijk AH, Willemse MP, Thijssen J, van Groningen JJ, Meltzer PS, van Kessel AG: The synovial-sarcoma-associated SS18-SSX2 fusion protein induces epigenetic gene (de)regulation. Cancer Res. 2006, 66: 9474-9482. 10.1158/0008-5472.CAN-05-3726.
Lubieniecka JM, de Bruijn DR, Su L, van Dijk AH, Subramanian S, van de Rijn M, Poulin N, van Kessel AG, Nielsen TO: Histone deacetylase inhibitors reverse SS18-SSX-mediated polycomb silencing of the tumor suppressor early growth response 1 in synovial sarcoma. Cancer Res. 2008, 68: 4303-4310. 10.1158/0008-5472.CAN-08-0092.
Erkizan HV, Uversky VN, Toretsky JA: Oncogenic partnerships: EWS-FLI1 protein interactions initiate key pathways of Ewing's sarcoma. Clin Cancer Res. 2010, 16: 4077-4083. 10.1158/1078-0432.CCR-09-2261.
Burdach S, Plehm S, Unland R, Dirksen U, Borkhardt A, Staege MS, Muller-Tidow C, Richter GH: Epigenetic maintenance of stemness and malignancy in peripheral neuroectodermal tumors by EZH2. Cell Cycle. 2009, 8: 1991-1996. 10.4161/cc.8.13.8929.
Riggi N, Suva ML, Suva D, Cironi L, Provero P, Tercier S, Joseph JM, Stehle JC, Baumer K, Kindler V, Stamenkovic I: EWS-FLI-1 expression triggers a Ewing's sarcoma initiation program in primary human mesenchymal stem cells. Cancer Res. 2008, 68: 2176-2185. 10.1158/0008-5472.CAN-07-1761.
Candelaria M, Herrera A, Labardini J, González-Fierro A, Trejo-Becerril C, Taja-Chayeb L, Pérez-Cárdenas E, de la Cruz-Hernández E, Arias-Bofill D, Vidal S, Cervera E, Dueñas-Gonzalez A: Hydralazine and magnesium valproate as epigenetic treatment for myelodysplastic syndrome. Preliminary results of a phase-II trial. Ann Hematol. 2010, 90: 379-387.
Fu S, Hu W, Iyer R, Kavanagh JJ, Coleman RL, Levenback CF, Sood AK, Wolf JK, Gershenson DM, Markman M, Hennessy BT, Kurzrock R, Bast RC: Phase 1b-2a study to reverse platinum resistance through use of a hypomethylating agent, azacitidine, in patients with platinum-resistant or platinum-refractory epithelial ovarian cancer. Cancer.
Vigil CE, Martin-Santos T, Garcia-Manero G: Safety and efficacy of azacitidine in myelodysplastic syndromes. Drug Des Devel Ther. 2010, 4: 221-229.
Fenaux P, Mufti GJ, Hellstrom-Lindberg E, Santini V, Finelli C, Giagounidis A, Schoch R, Gattermann N, Sanz G, List A, Gore SD, Seymour JF, Bennett JM, Byrd J, Backstrom J, Zimmerman L, McKenzie D, Beach C, Silverman LR, International Vidaza High-Risk MDS Survival Study Group: Efficacy of azacitidine compared with that of conventional care regimens in the treatment of higher-risk myelodysplastic syndromes: a randomised, open-label, phase III study. Lancet Oncol. 2009, 10: 223-232. 10.1016/S1470-2045(09)70003-8.
Kutko MC, Glick RD, Butler LM, Coffey DC, Rifkind RA, Marks PA, Richon VM, LaQuaglia MP: Histone deacetylase inhibitors induce growth suppression and cell death in human rhabdomyosarcoma in vitro. Clin Cancer Res. 2003, 9: 5749-5755.
Sakimura R, Tanaka K, Nakatani F, Matsunobu T, Li X, Hanada M, Okada T, Nakamura T, Matsumoto Y, Iwamoto Y: Antitumor effects of histone deacetylase inhibitor on Ewing's family tumors. Int J Cancer. 2005, 116: 784-792. 10.1002/ijc.21069.
Hurtubise A, Bernstein ML, Momparler RL: Preclinical evaluation of the antineoplastic action of 5-aza-2'-deoxycytidine and different histone deacetylase inhibitors on human Ewing's sarcoma cells. Cancer Cell Int. 2008, 8: 16-10.1186/1475-2867-8-16.
Fandy TE, Herman JG, Kerns P, Jiemjit A, Sugar EA, Choi SH, Yang AS, Aucott T, Dauses T, Odchimar-Reissig R, Licht J, McConnell MJ, Nasrallah C, Kim MK, Zhang W, Sun Y, Murgo A, Espinoza-Delgado I, Oteiza K, Owoeye I, Silverman LR, Gore SD, Carraway HE: Early epigenetic changes and DNA damage do not predict clinical response in an overlapping schedule of 5-azacytidine and entinostat in patients with myeloid malignancies. Blood. 2009, 114: 2764-2773.
Orzan F, Pellegatta S, Poliani L, Pisati F, Caldera V, Menghi F, Kapetis D, Marras C, Schiffer D, Finocchiaro G: Enhancer of Zeste 2 (Ezh2) is up-regulated in malignant gliomas and in glioma stem-like cells. Neuropathol Appl Neurobiol. 2010.
Yamaguchi J, Sasaki M, Sato Y, Itatsu K, Harada K, Zen Y, Ikeda H, Nimura Y, Nagino M, Nakanuma Y: Histone deacetylase inhibitor (SAHA) and repression of EZH2 synergistically inhibit proliferation of gallbladder carcinoma. Cancer Sci. 2010, 101: 355-362. 10.1111/j.1349-7006.2009.01387.x.
Fiskus W, Buckley K, Rao R, Mandawat A, Yang Y, Joshi R, Wang Y, Balusu R, Chen J, Koul S, Joshi A, Upadhyay S, Atadja P, Bhalla KN: Panobinostat treatment depletes EZH2 and DNMT1 levels and enhances decitabine mediated de-repression of JunB and loss of survival of human acute leukemia cells. Cancer Biol Ther. 2009, 8: 939-950. 10.4161/cbt.8.10.8213.
Hayden A, Johnson PW, Packham G, Crabb SJ: S-adenosylhomocysteine hydrolase inhibition by 3-deazaneplanocin A analogues induces anti-cancer effects in breast cancer cell lines and synergy with both histone deacetylase and HER2 inhibition. Breast Cancer Res Treat.
Kalushkova A, Fryknäs M, Lemaire M, Fristedt C, Agarwal P, Eriksson M, Deleu S, Atadja P, Osterborg A, Nilsson K, Vanderkerken K, Oberg F, Jernberg-Wiklund H: Polycomb target genes are silenced in multiple myeloma. PLoS One. 2010, 5: e11483-10.1371/journal.pone.0011483.
Fiskus W, Wang Y, Sreekumar A, Buckley KM, Shi H, Jillella A, Ustun C, Rao R, Fernandez P, Chen J, Balusu R, Koul S, Atadja P, Marquez VE, Bhalla KN: Combined epigenetic therapy with the histone methyltransferase EZH2 inhibitor 3-deazaneplanocin A and the histone deacetylase inhibitor panobinostat against human AML cells. Blood. 2009, 114: 2733-2743.
Tan J, Yang X, Zhuang L, Jiang X, Chen W, Lee PL, Karuturi RK, Tan PB, Liu ET, Yu Q: Pharmacologic disruption of Polycomb-repressive complex 2-mediated gene repression selectively induces apoptosis in cancer cells. Genes Dev. 2007, 21: 1050-1063. 10.1101/gad.1524107.
Wicha MS: Development of 'synthetic lethal' strategies to target BRCA1-deficient breast cancer. Breast Cancer Res. 2009, 11: 108-10.1186/bcr2362.
Viré E, Brenner C, Deplus R, Blanchon L, Fraga M, Didelot C, Morey L, Van Eynde A, Bernard D, Vanderwinden JM, Bollen M, Esteller M, Di Croce L, de Launoit Y, Fuks F: The Polycomb group protein EZH2 directly controls DNA methylation. Nature. 2006, 439: 871-874. 10.1038/nature04431.
Yu Y, Zeng P, Xiong J, Liu Z, Berger SL, Merlino G: Epigenetic drugs can stimulate metastasis through enhanced expression of the pro-metastatic Ezrin gene. PLoS One. 2010, 5: e12710-10.1371/journal.pone.0012710.
Herman JG, Gore S, Mufti G, Fenaux P, Santini V, Silverman L, Seymour J, Griffiths E, Caraway H, MacBeth K, Mckenzie D, Backstrom J, Beach CL: Abstract #4746: Relationship among gene methylation, azacitidine treatment, and survival in patients with higher-risk myelodysplastic syndromes (MDS): results from the AZA-001 trial. AACR Meeting Abstracts. 2009, American Association for Cancer Reasearch, Philadelphia, PA
Tuma RS: Epigenetic therapies move into new territory, but how exactly do they work?. J Natl Cancer Inst. 2009, 101: 1300-1301. 10.1093/jnci/djp342.
Demetri GD, von Mehren M, Blanke CD, Van den Abbeele AD, Eisenberg B, Roberts PJ, Heinrich MC, Tuveson DA, Singer S, Janicek M, Fletcher JA, Silverman SG, Silberman SL, Capdeville R, Kiese B, Peng B, Dimitrijevic S, Druker BJ, Corless C, Fletcher CD, Joensuu H: Efficacy and safety of imatinib mesylate in advanced gastrointestinal stromal tumors. New Eng J Med. 2002, 347: 472-480. 10.1056/NEJMoa020461.
Blanke CD, Rankin C, Demetri GD, Ryan CW, von Mehren M, Benjamin RS, Raymond AK, Bramwell VH, Baker LH, Maki RG, et al: Phase III randomized, intergroup trial assessing imatinib mesylate at two dose levels in patients with unresectable or metastatic gastrointestinal stromal tumors expressing the kit receptor tyrosine kinase: S0033. J Clin Oncol. 2008, 26: 626-632. 10.1200/JCO.2007.13.4452.
Demetri GD, van Oosterom AT, Garrett CR, Blackstein ME, Shah MH, Verweij J, McArthur G, Judson IR, Heinrich MC, Morgan JA, Desai J, Fletcher CD, George S, Bello CL, Huang X, Baum CM, Casali PG: Efficacy and safety of sunitinib in patients with advanced gastrointestinal stromal tumour after failure of imatinib: a randomised controlled trial. Lancet. 2006, 368: 1329-1338. 10.1016/S0140-6736(06)69446-4.
Mahmood ST, Agresta S, Vigil C, Zhao X, Han G, D'Amato G, Calitri CE, Dean M, Garrett C, Schell MJ, Antonia S, Chiappori A: Phase II study of sunitinib malate, a multi-targeted tyrosine kinase inhibitor in patients with relapsed or refractory soft tissue sarcomas. Focus on 3 prevalent histologies: Leiomyosarcoma, liposarcoma, and malignant fibrous histiocytoma. Int J Cancer.
George S, Merriam P, Maki RG, Van den Abbeele AD, Yap JT, Akhurst T, Harmon DC, Bhuchar G, O'Mara MM, D'Adamo DR, Morgan J, Schwartz GK, Wagner AJ, Butrynski JE, Demetri GD, Keohan ML: Multicenter phase II trial of sunitinib in the treatment of nongastrointestinal stromal tumor sarcomas. J Clin Oncol. 2009, 27: 3154-3160. 10.1200/JCO.2008.20.9890.
Keohan ML, Morgan JA, D'Adamo DR, Harmon D, Butrynski JE, Wagner AJ, Schwartz GK, Maki RG, Demetri GD, George S: Continuous daily dosing (CDD) of sunitinib (SU) in patients with metastatic soft tissue sarcomas (STS) other than GIST: Results of a phase II trial. ASCO Meeting Abstracts. 2008, American Society of Clinical Oncology, Alexandria, VA, 26 (Suppl): 10533.
Maki RG, Keohan ML, Undevia SD, Livingston M, Cooney MM, Elias A, Saulle MF, Wright JJ, D'Adamo DR, Schuetze SM, Sorafenib Sarcoma Study Group: Updated results of a phase II study of oral multi-kinase inhibitor sorafenib in sarcomas, CTEP study #7060. ASCO Meeting Abstracts. 2008, American Society of Clinical Oncology, Alexandria, VA, 26 (Suppl): 10531.
Ryan CW, von Mehren M, Rankin CJ, Goldblum JR, Demetri GD, Bramwell VH, Borden EC: Phase II intergroup study of sorafenib (S) in advanced soft tissue sarcomas (STS): SWOG 0505. ASCO Meeting Abstracts. 2008, American Society of Clinical Oncology, Alexandria, VA, 26 (Suppl): 10532.
Bertuzzi A, Stroppa EM, Secondino S, Pedrazzoli P, Zucali P, Quagliuolo V, Comandone A, Basso U, Soto Parra HJ, Santoro A: Efficacy and toxicity of sorafenib monotherapy in patients with advanced soft tissue sarcoma failing anthracycline-based chemotherapy. ASCO Meeting Abstracts. 2010, American Society of Clinical Oncology, Alexandria, VA, 28 (Suppl): 10025.
Sleijfer S, Ray-Coquard I, Papai Z, Le Cesne A, Scurr M, Schöffski P, Collin F, Pandite L, Marreaud S, De Brauwer A, van Glabbeke M, Verweij J, Blay JY: Pazopanib, a multikinase angiogenesis inhibitor, in patients with relapsed or refractory advanced soft tissue sarcoma: a phase II study from the European organisation for research and treatment of cancer-soft tissue and bone sarcoma group (EORTC study 62043). J Clin Oncol. 2009, 27: 3126-3132. 10.1200/JCO.2008.21.3223.
Demetri GD, Casali PG, Blay JY, von Mehren M, Morgan JA, Bertulli R, Ray-Coquard I, Cassier P, Davey M, Borghaei H, Pink D, Debiec-Rychter M, Cheung W, Bailey SM, Veronese ML, Reichardt A, Fumagalli E, Reichardt P: A phase I study of single-agent nilotinib or in combination with imatinib in patients with imatinib-resistant gastrointestinal stromal tumors. Clin Cancer Res. 2009, 15: 5910-5916. 10.1158/1078-0432.CCR-09-0542.
Okuno S, Bailey H, Mahoney MR, Adkins D, Maples W, Fitch T, Ettinger D, Erlichman C, Sarkaria JN: A phase 2 study of temsirolimus (CCI-779) in patients with soft tissue sarcomas: A study of the mayo phase 2 consortium (P2C). Cancer. 2011.
Richter S, Pink D, Hohenberger P, Schuette H, Casali PG, Pustowka A, Reichardt P: Multicenter, triple-arm, single-stage, phase II trial to determine the efficacy and safety of everolimus (RAD001) in patients with refractory bone or soft tissue sarcomas including GIST. ASCO Meeting Abstracts. 2010, American Society of Clinical Oncology, Alexandria, VA, 28 (Suppl): 10038.
Mita MM, Britten CD, Poplin E, Tap WD, Carmona A, Yonemoto L, Wages DS, Bedrosian CL, Rubin EH, Tolcher AW: Deforolimus trial 106- A Phase I trial evaluating 7 regimens of oral Deforolimus (AP23573, MK-8669). ASCO Meeting Abstracts. 2008, 26 (Suppl): 3509..
Chawla SP, Tolcher AW, Staddon AP, Schuetze S, D'Amato GZ, Blay JY, Loewy J, Kan R, Demetri GD: Survival results with AP23573, a novel mTOR inhibitor, in patients (pts) with advanced soft tissue or bone sarcomas: Update of phase II trial. ASCO Meeting Abstracts. 2007, 2: 5(Suppl):10076.
Anonymous: Ridaforolimus. Drugs R&D. 2010, 10: 165-178.
Olmos D, Postel-Vinay S, Molife LR, Okuno SH, Schuetze SM, Paccagnella ML, Batzel GN, Yin D, Pritchard-Jones K, Judson I, Worden FP, Gualberto A, Scurr M, de Bono JS, Haluska P: Safety, pharmacokinetics, and preliminary activity of the anti-IGF-1R antibody figitumumab (CP-751,871) in patients with sarcoma and Ewing's sarcoma: a phase 1 expansion cohort study. Lancet Oncol. 2010, 11: 129-135. 10.1016/S1470-2045(09)70354-7.
Patel S, Pappo A, Crowley J, Reinke D, Eid J, Ritland S, Chawla S, Staddon A, Maki R, Vassal G, Helman L, Sarcoma Alliance for Research and Collaboration: A SARC global collaborative phase II trial of R1507, a recombinant human monoclonal antibody to the insulin-like growth factor-1 receptor (IGF1R) in patients with recurrent or refractory sarcomas. ASCO Meeting Abstracts. 2009, 27 (Suppl): 10503..
Tolcher AW, Sarantopoulos J, Patnaik A, Papadopoulos K, Lin CC, Rodon J, Murphy B, Roth B, McCaffery I, Gorski KS, Kaiser B, Zhu M, Deng H, Friberg G, Puzanov I: Phase I, pharmacokinetic, and pharmacodynamic study of AMG 479, a fully human monoclonal antibody to insulin-like growth factor receptor 1. J Clin Oncol. 2009, 27: 5800-5807. 10.1200/JCO.2009.23.6745.
Scartozzi M, Bianconi M, Maccaroni E, Giampieri R, Berardi R, Cascinu S: Dalotuzumab, a recombinant humanized mAb targeted against IGFR1 for the treatment of cancer. Curr Opin Mol Ther. 2010, 12: 361-371.
The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1741-7015/9/63/prepub
The present work was supported by grants from Ministero della Sanità Italia (Ricerca Corrente), Associazione Italiana per la Ricerca sul Cancro (AIRC Project 10338) and Istituto Superiore di Sanità (ISS Project 70BF/8) to RR and by grants from Ministero della Salute, Italia (Ricerca Corrente) and AIRC (Special Project 5 × mille) to FL.
The authors declare that they have no competing interests.
RC and RR contributed equally to selection and discussion of the literature and the conception and preparation of the manuscript. FL, AG and LM contributed to the discussion on clinical implications and reviewed the manuscript. All authors read and approved the final manuscript.
About this article
Cite this article
Ciarapica, R., Miele, L., Giordano, A. et al. Enhancer of zeste homolog 2 (EZH2) in pediatric soft tissue sarcomas: first implications. BMC Med 9, 63 (2011). https://doi.org/10.1186/1741-7015-9-63
- soft tissue sarcomas