ACLS
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Zenali, M. J.
Right arrow Articles by Brown, R. E.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Zenali, M. J.
Right arrow Articles by Brown, R. E.
Annals of Clinical & Laboratory Science 39:160-166 (2009)
© 2009 Association of Clinical Scientists

Morphoproteomic Confirmation of Constitutively Activated mTOR, ERK, and NF-kappaB Pathways in Ewing Family of Tumors

Maryam J. Zenali1, Ping L. Zhang2, Anne E. Bendel3 and Robert E. Brown1
1 Department of Pathology and Laboratory Medicine, University of Texas-Houston Medical School; 2 Department of Anatomic Pathology, William Beaumont Hospital, Royal Oak, Michigan; and 3 Pediatric Hematology/Oncology, Children’s Hospitals and Clinics, Minneapolis, Minnesota

Address correspondence to Robert E. Brown, M.D., Department of Pathology and Laboratory Medicine, University of Texas Health Science Center-Medical School at Houston, 6431 Fannin Street, MSB 2.286, Houston, TX 77030, USA; tel 713 500 5332; fax 713 500 0695; e-mail robert.brown{at}uth.tmc.edu.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results and Discussion
 References
 
In 3 patients with the Ewing family of tumors (EFT), morphoproteomic analyses of the tumors revealed constitutive activation of the mTOR, ERK, and NF-kappaB pathways, as evidenced by: (a) expression of phosphorylated (p)-mTOR, p-p70S6K, p-ERK 1/2, and p-NF-kappaB proteins using phosphospecific immunohistochemical probes directed against the activation sites; (b) nuclear translocation of p-p70S6K, p-ERK 1/2, and p-NF-kappaBp65; and (c) correlative expression of Ki-67 and Skp2 proteins consistent with cell cycling consequent to signal transduction by these pathways of convergence. This study examines the cytogenetic and molecular correlates and provides insight into therapeutic strategies relevant to this morphoproteomic profile. Based on a literature review, these observations appear to be the first morphoproteomic study of such pathways of convergence in tumors from EFT patients.

Keywords: Ewing family of tumors, mTOR, p70S6K, ERK, NF-kappaB, cell cycle, morphoproteomics


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results and Discussion
 References
 
Ewing family of tumors (EFT) comprises Ewing’s sarcoma and primitive neuroectodermal tumor. EFT is an aggressive pediatric tumor; in patients with metastatic disease, the 5-yr survival rate is <30% [1], emphasizing the need for new therapeutic strategies. EFT, when characterized cytogenetically, has been associated with multiple translocations fusing the EWS gene on chromosome 22 to a subset of ETS transcription factor family members, namely FLI1 (on chromosome 11), ETV1 (on chromosome 7), and ERG ( on chromosome 21) [2,3]. Molecular studies confirm that fusion of EWS to different ETS family genes promotes oncogenesis via similar biological pathways. The fusions all result in repression of transforming growth factor (TGF)-beta receptor (R) II, a putative tumor suppressor gene [2,4]. In cell lines, EFT’s most common fusion oncogene, EWS-FLI1, has been associated with activation of mammalian target of rapamycin (mTOR) and of members of the mitogen-activated protein kinase (MAPK) signaling pathway, and, specifically, extracellular signal-regulated kinases (ERK) 1 and 2. The latter occurs via activation of mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK 1) [5,6]. In keeping with these observations, rapamycin treatment has resulted in time-dependent progressive decrease of p70S6K, a downstream effector in the mTOR pathway and in EWS/FLI1 proteins. The decrease of p70S6K was accompanied by a marked increase of TGF-beta RII mRNA levels and inhibition of EFT cell line proliferation [5]. Another study showed that interference of MEK1 signaling by a specific inhibitor, PD98059, led to a decrease in ERK activation by EWS-FLI1 and a remarkable decrease in the number of cell line colonies [6]. Similarly, the common fusion oncogenes in EFT have been implicated in tumorigenicity via upregulation of nuclear factor (NF)-kappaB and its anti-apoptotic effects by p21 induction [7]. These observations stimulated us to use morphoproteomics [8] to investigate the state of activation of components of the m-TOR, ERK, and NF-kappaB pathways and the cell cycle, cytogenetic, and molecular correlates in 3 archival EFT cases.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results and Discussion
 References
 
With Institutional Review Board (IRB) approval, we studied archival paraffin-embedded tissue blocks from three cases of EFT. The patients all had metastatic disease to the lung or to mediastinum at diagnosis or recurrence. Immunohistochemical (IHC) probes were utilized for the detection of the following 4 phosphorylated (p) antigens: p-mTOR (Ser 2448) and one of its downstream effectors, p-p70S6K (Thr 389); p- ERK 1/2 (Thr 202/Tyr 204); p-NF-kappaBp65 (Ser 536) (Cell Signaling Technology, Beverly, MA) and 2 cell cycle-associated proteins, Ki-67, and S phase kinase-asssociated protein, Skp2 (Dako Corporation, Carpinteria, CA, and Santa Cruz Biotechnology, Santa Cruz, CA, respectively).

Chromogenic signal and subcellular compartmentalization (plasmalemmal, cytoplasmic, and/or nuclear) were assessed by bright-field microscopy on a scale of 0–3+; the Ki-67 proliferation index and Skp2 nuclear expression were quantified by an automated cellular imaging system (ACIS). Positive and negative IHC controls run concurrently reacted appropriately.

The average mitotic index per 10 high power fields was obtained for each of the 3 cases by counting the number of mitotic figures in sets of 10 consecutive high power fields and then determining the arithmetic mean of mitotic figures for each case. In 2 of the patients, cytogenetic/molecular studies were performed on concurrent tumor specimens.


   Results and Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results and Discussion
References
 
Moderate to strong expressions (up to 2–3+ on a scale of 0–3+) of p-mTOR (Ser 2448) and p-p70S6K (Thr 389), of p-ERK 1/2 (Thr 202/Tyr 204), and of p-NF-kappaBp65 (Ser 536) were evident in tumor cells from all 3 cases. Additionally, consistent nuclear translocation of the latter 3 analytes was also noted (Fig. 1Go); the nuclear and cytoplasmic expressions of p-mTOR were variable among the cases. Automated cellular imaging with quantification of Ki-67 and Skp2 chromogenic signals revealed nuclear reactivity in 10%, 10%, and 37% and 13%, 16% and 20%, respectively, in cases 1–3. The corresponding average mitotic indices of the 3 cases were 8, 8, and 19 mitotic figures per 10 high power fields (HPF’s). An example of Skp2 expression in case 3 is shown in Fig. 2Go. In one tumor, cytogenetic and molecular analyses revealed translocation involving chromosomes 7 and 22, t(7;22), which has been associated with EWS/ETV1 fusion; in another tumor, the analyses revealed a EWS/FLI transcript involving chromosomes 11 and 22, t(11;22).


Figure 1
View larger version (155K):
[in this window]
[in a new window]

  		Fig.1. Hematoxylin and eosin (H & E) stained section of an Ewing family of tumors (EFT) case (top left frame); plasmalemmal CD99 upstream signal transducer (top right frame); and immunohistochemical phosphospecific probes for p-ERK 1/2 phosphorylated on threonine 202/tyrosine 204 (middle left frame); for p-mTOR phosphorylated on serine 2448 (middle right frame) and for its downstream effector, p-p70S6K phosphorylated on threonine 389 (lower left frame); and for p-NF-kappaBp65 phosphorylated on serine 536 (lower right frame); all of the latter reveal variably moderate to strong brown (DAB chromogen) signal intensity in tumor cells, Nuclear translocation of p-ERK 1/2, p-p70S6K, and p-NF-kappaBp65 provides additional morphorproteomic evidence of constitutive activation of these protein analytes. (Original magnification X600.)

 

Figure 2
View larger version (127K):
[in this window]
[in a new window]

  		Fig. 2. Nuclear expression with variable brown DAB chromogenic signal of the S phase kinase-associated protein, Skp2, in a case of Ewing family of tumors (EFT) (original magnification X100). Quantitation using an automated cellular imaging system (DAKO ACISIII) reveals a percent positive nuclear average of 20% (Inset).

 
Morphoproteomics utilizes phosphospecific probes and cellular compartmentalization to assess directly the state of activation of protein analytes in lesional tissues [8]. In the EFT cases in this study, this approach confirmed the constitutive activation of mTOR phosphorylated on serine 2448, and of its substrate, p70S6K, phosphorylated on threonine 389. This set of findings points to downstream signal transduction through the phosphatidylinositol 3'-kinase (PI3'-K)/Akt/mTOR pathway [9–16]. Moreover, based on a review of the literature, upstream activation of the mTOR pathway could reflect insulin-like growth factor receptor I (IGF-IR) and also integrin-linked kinase (ILK) signaling in EFT [17–18].

The IGF-IR mediated circuit has been implicated as a major autocrine loop for EFT, with upregulation of vascular endothelial growth factor (VEGF)-A and modulation of angiogenesis through the PI3'K and MAPK signaling pathways [17]. Ezrin is reported to mediate growth and survival in EFT through the Akt/mTOR pathway [1]. ILK, a multi-domain focal adhesion protein kinase regulating integrin-mediated signal transduction, and proposed as a useful marker for positive identification of EFT, has been shown to phosphorylate Akt at serine 473 in vitro and to activate its downstream targets including mTOR [18–20]. ILK may also be involved in the phosphorylation of ERK 1/2 [21]. CD99, one of the diagnostic immunophenotypic markers for EFT (see Fig. 1Go), might also participate in the signaling process by contributing to the phosphorylative activation of ERK [22].

The relatively high percentages of Ki-67 and Skp2 and of corresponding mitotic indices in these 3 cases are consistent with cell cycling consequent to the aforementioned activated signal transduction pathways. To expand on this, Ki-67 is a generic marker for cell cycling beyond the G0 phase and is expressed in G1, S, G2, and M phases, while Skp2 defines cells in the S phase [23,24]. Preclinical/experimental studies by Gao and colleagues [25] and Edelmann and co-workers [26] support the contention that constitutively activated mTOR and ERK pathway signaling promote G1 to S phase cell cycle progression and thereby agree with our morphoprotoemic findings in the EFT cases. Similarly, the constitutive activation of the NF-kappaB pathway in our cases is consistent with convergent signaling by the mTOR and ERK pathways [8,27].

In 1 of 3 EFT patients in this study, the finding of a fusion transcript of EWS/FLI provides a molecular correlate for the morphoproteomic finding of constitutively activated mTOR and ERK pathways in this patient [5,6]. Finally, from prognostic and tumorigenic standpoints, the following observations are noteworthy: (1) Amir et al [28] defined overexpression of Ki-67 in EFT as >8.3% malignant cell nuclei and showed a shorter median relapse-free survival in EFT with positive Ki-67 staining than in patients with negative staining (ie, 40 vs 80 mo) but this difference did not reach statistical significance; (2) Huuhtanen and co-authors [29] reported on the S-phase fraction as measured by flow cytometry in soft tissue sarcomas including 10 cases of extraskeletal EFT, noting a range of 2.6 to 21.9% in the latter and a shorter overall survival for patients with diploid tumors and a high S-phase fraction (>5.6%) (9 of the 10 EFT cases were diploid); (3) Matsunobu and co-workers [30] showed an inverse relationship between the IHC expression levels of p27 and Skp2 proteins in EFT samples and because of their findings from small interfering RNA studies, suggested an important role for EWS-FLI1 in the prevention of senescence through decreased stability of p27 protein due to the increased action of Skp2-mediated 26S proteasome degradation of this cell cycle inhibitor (it has been proposed that this effect leads to unlimited growth and the oncogenesis of such tumor cells); and (4) Javelaud and co-authors reported that inhibition of constitutive NF-kappaB activity suppressed the tumorigenicity of EFT cells in a xenograft model [7].

Therapeutic considerations raised by our morphoproteomic findings include the use of one or more small molecule inhibitors to target the constitutively activated mTOR/ERK and NF-kappaB pathways in EFT. Such inhibitors include rapamycin or a rapamycin analog, sorafenib, a Raf kinase/ERK pathway inhibitor, and bortezomib, respectively [8]. A computer-assisted search of the MEDLINE database provided the following support for this approach in EFT: (1) as noted previously, rapamycin can induce the fusion-type independent downregulation of the EWS/FLI1 proteins while promoting cell cycle arrest at the G1 phase in EFT cells [5]; (2) a phase I trial using deforolimus, a nonprodrug rapamycin analog, resulted in a partial clinical response in a patient with EFT [31]; (3) interference with the constitutive activation of ERK 1 and ERK 2 impairs EWS/FLI1-dependent transformation in EFT cells; and (4) inhibition of constitutive NF-kappaB activity suppresses tumorigenicity of EFT cells [7]. A schematic summary of our morphoproteomic observations and the potential therapeutic opportunities is presented in Fig. 3Go.


Figure 3
View larger version (44K):
[in this window]
[in a new window]

  		Fig. 3. Diagrammatic representation of the signal transduction pathways (red lettering and arrows) identified by the authors and others in the Ewing family of tumors (EFT) (analytes are designated with asterisks *). Specifically, downstream signaling by insulin-like growth factor (IGF)-I and its receptors (IGF-IR)[facilitated by EWS/FLI-1 fusion protein] and beta-integrin-linked protein kinase (ILK) would proceed through the PI3-K/Akt and ras/Raf Kinase/ERK pathways. Ezrin would contribute to Akt signaling and CD 99 to the activation of the ERK pathway. This would be manifested by mTOR pathway activation (p-mTOR and p-p70S6K expressions) and constitutive activation of ERK (p-ERK 1/2 expression with nuclear translocation). Convergent signaling would result in constitutive NF-kappaBp65 activation (p-NF-kappaBp65 expression); such signaling would result in G1 to S phase cell cycle progression with Skp2 expression and mitoses and vascular endothelial growth factor (VEGF) expression. Opportunities for therapeutic intervention (blue bar) might include combinatorial therapies with an S-phase active agent, a Raf kinase inhibitor (sorafenib), an mTOR inhibitor (rapamycin), and/or a proteasome inhibitor (bortezomib).

Abbreviations: IGR-IR: insulin-like growth factor type I receptor; PI3'-K: phosphatidylinositol 3'-kinase; mTOR: mammalian target of rapamycin; ERK: extracellular signal-regulated kinase; IKK: Inhibitor kappaB kinase; I-kappaB: inhibitor-kappaB; NF- kappaB: nuclear factor-kappaB; Skp-2: S phase-associated protein kinase.

 
Although the use of small molecule inhibitors of these signal transduction pathways may certainly be used in a combinatorial fashion with cytotoxic therapies that target the S phase or G2/M phases of the cell cycle as appropriate in individual EFT patients to effect a reduction in the tumor burden, we must also be mindful of recent evidence of a mesenchymal stem cell origin for EFT [32,33] and the therapeutic challenges that this poses in those individual cases in which a tumoral stem cell component can be identified by morphoproteomic analysis [34].

In summary, our morphoproteomic studies reveal constitutive activation of mTOR, ERK, and NF-kappaB signal transduction pathways and the correlative expression of cell cycle analytes and parameters indicative of G1 to S and G2/M cell cycle progression consequent to such signaling in EFT tumor family cases. Although such findings are preliminary, based on a review of the literature these observations appear to be the first on primary EFT specimens. Moreover, our findings agree with reports concerning upstream signal transducers of these pathways of convergence and with cytogenetic/molecular concomitants in EFT, and offer a starting point for studies of a larger series of cases and for the design of clinical trials using small molecule inhibitors and S phase and/or G2/M cytotoxic therapies in a combinatorial fashion against EFT.


   Acknowledgments
 
The authors thank Richard A. Breckenridge, HT (ASCP), and Pamela K. Johnston, HT (ASCP), for technical assistance and Bheravi Patel for secretarial support and help with the graphics.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results and Discussion
 References
 

  1. Krishnan K, Bruce B, Hewitt S, Thomas D, Khanna C, Helman LJ. Ezrin mediates growth and survival in Ewing’s sarcoma through the AKT/mTOR, but not the MAPK, signaling pathway. Clin Exp Metastasis 2006; 23:227–236.[Medline]
  2. Im YH, Kim HT, Lee C, Poulin D, Welford S, Sorensen PH, Denny CT, Kim SJ. EWS-FLI1, EWS-ERG, and EWS-ETV1 oncoproteins of Ewing tumor family all suppress transcription of transforming growth factor beta type II receptor gene. Cancer Res 2000;60:1536–1540.[Abstract/Free Full Text]
  3. Jeon IS, Davis JN, Braun BS, Sublett JE, Roussel MF, Denny CT, Shapiro DN. A variant Ewing’s sarcoma translocation (7; 22) fuses the EWS gene to the ETS gene ETV1. Oncogene 1995;10:1229–1234.[Medline]
  4. Thompson AD, Teitell MA, Arvand A, Denny CT. Divergent Ewing’s sarcoma EWS/ETS fusions confer a common tumorigenic phenotype on NIH3T3 cells. Oncogene 1999;18:5506–5513.[Medline]
  5. Mateo-Lozano S, Tirado OM, Notario V. Rapamycin induces the fusion-type independent downregulation of the EWS/FLI-1 proteins and inhibits Ewing’s sarcoma cell proliferation. Oncogene 2003;22:9282–9287.[Medline]
  6. Silvany RE, Eliazer S, Wolff NC, Ilaria RL Jr. Interference with the constitutive activation of ERK1 and ERK2 impairs EWS/FLI-1-dependent transformation. Oncogene 2000;19:4523–4530.[Medline]
  7. Javelaud D, Poupon MF, Wietzerbin J, Besancon F. Inhibition of constitutive NF-kappa B activity suppresses tumorigenicity of Ewing sarcoma EW7 cells. Int J Cancer 2002;98:193–198.[Medline]
  8. Brown RE. Morphoproteomics: exposing protein circuitries in tumors to identify potential therapeutic targets in cancer patients. Expert Rev Proteomics 2005; 2:337–348.[Medline]
  9. Cao X, Kambe F, Moeller LC, Refetoff S, Seo H. Thyroid hormone induces rapid activation of Akt/protein kinase B-mammalian target of rapamycin-p70S6K cascade through phosphatidylinositol 3–kinase in human fibroblasts. Mol Endocrinol 2005;19:102–112.[Abstract/Free Full Text]
  10. Nave BT, Ouwens M, Withers DJ, Alessi DR, Shepherd PR. Mammalian target of rapamycin is a direct target for protein kinase B: identification of a convergence point for opposing effects of insulin and amino-acid deficiency on protein translation. Biochem J 1999;344: 427–431.[Medline]
  11. Pullen N, Dennis PB, Andjelkovic M, Dufner A, Kozma SC, Hemmings BA, Thomas G. Phosphorylation and activation of p70s6k by PDK1. Science 1998;279:707–710.[Abstract/Free Full Text]
  12. Dennis PB, Pullen N, Kozma SC, Thomas G. The principal rapamycin-sensitive p70 (s6k) phosphorylation sites, T-229 and T-389, are differentially regulated by rapamycin-insensitive kinase kinases. Mol Cell Biol 1996;16:6242–6251.[Abstract/Free Full Text]
  13. Valentinis B, Navarro M, Zanocco-Marani T, Edmonds P, McCormick J, Morrione A, Sacchi A, Romano G, Reiss K, Baserga R. Insulin receptor substrate-1, p70S6K, and cell size in transformation and differentiation of hemopoietic cells. J Biol Chem 2000;275:25451–25459.[Abstract/Free Full Text]
  14. Xu G, Zhang W, Bertram P, Zheng XF, McLeod H. Pharmacogenomic profiling of the PI3K/PTEN-AKT-mTOR pathway in common human tumors. Int J Oncol 2004;24:893–900.[Medline]
  15. Ali SM, Sabatini DM. Structure of S6 kinase 1 determines whether raptor-mTOR or rictor-mTOR phosphorylates its hydrophobic motif site. J Biol Chem 2005; 280:19445–19448.[Abstract/Free Full Text]
  16. Kim SJ, Kahn CR. Insulin stimulates p70 S6 kinase in the nucleus of cells. Biochem Biophys Res Commun 1997;234:681–685.[Medline]
  17. Strammiello R, Benini S, Manara MC, Perdichizzi S, Serra M, Spisni E, Picci P, Scotlandi K. Impact of IGF-I/IGF-IR circuit on the angiogenetic properties of Ewing’s sarcoma cells. Horm Metab Res 2003;35:675–684.[Medline]
  18. Chung DH, Lee JI, Kook MC, Kim JR, Kim SH, Choi EY, Park SH, Song HG. ILK (beta1-integrin-linked protein kinase): a novel immunohistochemical marker for Ewing’s sarcoma and primitive neuroectodermal tumour. Virchows Arch 1998;433:113–117.[Medline]
  19. Tan C, Cruet-Hennequart S, Troussard A, Fazli L, Costello P, Sutton K, Wheeler J, Gleave M, Sanghera J, Dedhar S. Regulation of tumor angiogenesis by integr-inlinked kinase (ILK). Cancer Cell 2004;5:79–90.[Medline]
  20. Koul D, Shen R, Bergh S, Lu Y, de Groot JF, Liu TJ, Mills GB, Yung WK. Targeting integrin-linked kinase inhibits Akt signaling pathways and decreases tumor progression of human glioblastoma. Mol Cancer Ther 2005;4:1681–1688.[Abstract/Free Full Text]
  21. Zhang Y, Ikegami T, Honda A, Miyazaki T, Bouscarel B, Rojkind M, Hyodo I, Matsuzaki Y. Involvement of integrin-linked kinase in carbon tetrachloride-induced hepatic fibrosis in rats. Hepatology 2006;44:612–622.[Medline]
  22. Hahn MJ, Yoon SS, Sohn HW, Song HG, Park SH, Kim TJ. Differential activation of MAP kinase family members triggered by CD99 engagement. FEBS Lett 2000;470:350–354.[Medline]
  23. Gaglia P, Bernardi A, Venesio T, Caldarola B, Lauro D, Cappa AP, Calderini P, Liscia DS. Cell proliferation of breast cancer evaluated by anti-BrdU and anti-Ki-67 antibodies: its prognostic value on short-term recurrences. Eur J Cancer 1993;29A:1509–1513.
  24. Chiarle R, Fan Y, Piva R, Boggino H, Skolnik J, Novero D, Palestro G, De Wolf-Peeters C, Chilosi M, Pagano M, Inghirami G. S-phase kinase-associated protein 2 expression in non-Hodgkin’s lymphoma inversely correlates with p27 expression and defines cells in S phase. Am J Pathol 2002;160:1457–1466.[Medline]
  25. Gao N, Flynn DC, Zhang Z, Zhong XS, Walker V, Liu KJ, Shi X, Jiang BH. G1 cell cycle progression and the expression of G1 cyclins are regulated by PI3K/AKT/mTOR/p70S6K1 signaling in human ovarian cancer cells. Am J Physiol Cell Physiol 2004;287:C281–291.[Abstract/Free Full Text]
  26. Edelmann HM, Kühne C, Petritsch C, Ballou LM. Cell cycle regulation of p70 S6 kinase and p42/p44 mitogen-activated protein kinases in Swiss mouse 3T3 fibroblasts. J Biol Chem 1996;271:963–971.[Abstract/Free Full Text]
  27. Dan HC, Cooper MJ, Cogswell PC, Duncan JA, Ting JP, Baldwin AS. Akt-dependent regulation of NF-{kappa}B is controlled by mTOR and raptor in association with IKK. Genes Dev 2008;22:1490–1500.[Abstract/Free Full Text]
  28. Amir G, Issakov J, Meller I, Sucher E, Peyser A, Cohen IJ, Yaniv I, Ben Arush MW, Tavori U, Kollender Y, Ron N, Peylan-Ramu N. Expression of p53 gene product and cell proliferation marker Ki-67 in Ewing’s sarcoma: correlation with clinical outcome. Hum Pathol 2002;33: 170–174.[Medline]
  29. Huuhtanen RL, Blomqvist CP, Wiklund TA, Virolainen MJ, Elomaa AI, Pan Y, Tribukait B. S-phase fraction of 155 soft tissue sarcomas: correlation with clinical outcome. Cancer 1996;77:1815–1822.[Medline]
  30. Matsunobu T, Tanaka K, Nakamura T, Nakatani F, Sakimura R, Hanada M, Li X, Okada T, Oda Y, Tsuneyoshi M, Iwamoto Y. The possible role of EWSFli1 in evasion of senescence in Ewing family tumors. Cancer Res 2006;66:803–811.[Abstract/Free Full Text]
  31. Mita MM, Mita AC, Chu QS, Rowinsky EK, Fetterly GJ, Goldston M, Patnaik A, Mathews L, Ricart AD, Mays T, Knowles H, Rivera VM, Kreisberg J, Bedrosian CL, Tolcher AW. Phase I trial of the novel mammalian target of rapamycin inhibitor deforolimus (AP23573; MK-8669) administered intravenously daily for 5 days every 2 weeks to patients with advanced malignancies. J Clin Oncol 2008;26:361–367.[Abstract/Free Full Text]
  32. Riggi N, Suvà ML, Suvà 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.[Abstract/Free Full Text]
  33. Burns JS, Abdallah BM, Shrøder HD, Kassem M. The histopathology of a human mesenchymal stem cell experimental tumor model: support for an hMSC origin for Ewing’s sarcoma? Histol Histopathol 2008; 23:1229–1240.[Medline]
  34. Alison MR, Murphy G, Leedham S. Stem cells and cancer: a deadly mix. Cell Tissue Res 2008;331:109–124.[Medline]




This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Zenali, M. J.
Right arrow Articles by Brown, R. E.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Zenali, M. J.
Right arrow Articles by Brown, R. E.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS