Journal of Molecular Medicine

, Volume 85, Issue 1, pp 23–38 | Cite as

Proliferation and cell–cell fusion of endometrial carcinoma are induced by the human endogenous retroviral Syncytin-1 and regulated by TGF-β

  • Reiner StrickEmail author
  • Sven Ackermann
  • Manuela Langbein
  • Justine Swiatek
  • Steffen W. Schubert
  • Said Hashemolhosseini
  • Thomas Koscheck
  • Peter A. Fasching
  • Ralf L. Schild
  • Matthias W. Beckmann
  • Pamela L. Strissel
Original Article


Endometrial carcinomas (EnCa) predominantly represent a steroid hormone-driven tumor initiated from prestages. The human endogenous retrovirus HERV-W envelope gene Syncytin-1 was significantly increased at the mRNA and protein levels in EnCa and prestages compared to controls. Steroid hormone treatment of primary EnCa cells and cell lines induced Syncytin-1 due to a new HERV-W estrogen response element and resulted in increased proliferation. Activation of the cAMP-pathway also resulted in Syncytin-1 upregulation, but in contrast to proliferation, classic cell–cell fusions similar to placental syncytiotrophoblasts occurred. Cell–cell fusions were also histologically identified in endometrioid EnCa tumors in vivo. Clonogenic soft agar experiments showed that Syncytin-1 is also involved in anchorage-independent colony growth as well as in colony fusions depending on steroid hormones or cAMP-activation. The posttranscriptional silencing of Syncytin-1 gene expression and a concomitant functional block of induced cell proliferation and cell–cell fusion with siRNAs proved the essential role of Syncytin-1 in these cellular processes. TGF-β1 and TGF-β3 were identified as main regulative factors, due to the finding that steroid hormone inducible TGF-β1 and TGF-β3 inhibited cell–cell fusion, whereas antibody-mediated TGF-β neutralization induced cell–cell fusions. These results showed that induced TGF-β could override Syncytin-1-mediated cell–cell fusions. Interactions between Syncytin-1 and TGF-β may contribute to the etiology of EnCa progression and also help to clarify the regulation of cell–cell fusions occurring in development and in other syncytial cell tumors.


Tumorigenesis HERV Endometrial carcinoma Cell fusion TGF-beta 



The authors are especially grateful to the patients who participated in this study and to the Department of Gynaecology, Erlangen. The authors wish to thank Prof. Dr. Papadopoulos at the Institute for Pathology, University of Erlangen for the histology of the tissue samples, Prof. Dr. C-M Becker (Institute for Biochemistry, University of Erlangen) for the use of the isotope laboratory, Mrs. Wenzel (Institute for Biochemistry) for cloning and sequencing, Mrs. Staerker and Toborek for hCG determinations, and Mrs. Oeser and Stiegler (Department of Gynecology) for their expert technical assistance. This study was partially supported by a grant from the DFG (#555/2-1).

Supplementary material

109_2006_104_MOESM1_ESM.doc (21 kb)
Supplemental Table 1 (DOC 21 kb)
109_2006_104_MOESM2_ESM.doc (22 kb)
Supplemental Table 2 (DOC 22 kb)
109_2006_104_Fig1_ESM.jpg (122 kb)
supplemental Fig. S1

Growth curves of BeWo, Kle, and RL95-2 cells in the presence of different steroid hormones, ddA or Forskolin. Open circle control, open triangle 10 nM E2, closed triangle 10 nM 4-OH-E2, closed square 1 μM estrone, cross 10 nM 2-OH-E2, closed circle 1 μM Estriol, closed diamond 10 mM ddA plus 10 nM E2, open square 500 nM progesterone, open diamond 40 μM Forskolin (JPEG 125 kb)

109_2006_104_Fig2a-b_ESM.jpg (80 kb)
supplemental Fig. S2

a RT-PCR of Syncytin-1 (748 bp) and β-actin (382 bp) with RNA isolated from RL95-2 cells treated with 10 nM of either E2, 4OH-E2 (4E2), or 2OH-E2 (2E2), 1 μM estrone (E1), and 10 nM E2 plus 10 mM ddA. M DNA marker. b RT-PCR of Syncytin-1 (748 bp) and β-actin (382 bp) with RNA isolated from Syncytin-1 transfected RL95-2 cells at 4 days post transfection (c1). After 4 days post transfection the cells were cultivated for an additional 3 days (c), and treated with 10 nM E2 or 40 μM Forskolin (F) (JPEG 82 kb)

109_2006_104_Fig3_ESM.jpg (207 kb)
supplemental Fig. S3

Cultured BeWo cells were incubated with 10 nM E2 (E2), 40 μM SP-cAMP (SP-cAMP), 40 μM SP-cAMP plus 5 ng/ml TGF-β1 (SP-cAMP + TGF-β1), and 10 nM E2 plus 1 μg/ml anti-TGF-β1 (E2 + anti-TGF-β1), then stained with May–Grunwald and Giemsa (JPEG 211 kb)


  1. 1.
    Ellenson LH, Wu TC (2004) Focus on endometrial and cervical cancer. Cancer Cell 5:533–538PubMedCrossRefGoogle Scholar
  2. 2.
    Jemal A, Tiwari RC, Murray T et al (2004) Cancer statistics, 2004. CA Cancer J Clin 54:8–29PubMedCrossRefGoogle Scholar
  3. 3.
    Sherman ME (2000) Theories of endometrial carcinogenesis: a multidisciplinary approach. Mod Pathol 13:295–308PubMedCrossRefGoogle Scholar
  4. 4.
    Horn LC, Schnurrbusch U, Bilek K, Hentschel B, Einenkel J (2004) Risk of progression in complex and atypical endometrial hyperplasia: clinicopathologic analysis in cases with and without progestogen treatment. Int J Gynecol Cancer 14:348–353PubMedCrossRefGoogle Scholar
  5. 5.
    Anastasiadis PG, Koutlaki NG, Skaphida PG, Galazios GC, Tsikouras PN, Liberis VA (2000) Endometrial polyps: prevalence, detection, and malignant potential in women with abnormal uterine bleeding. Eur J Gynaecol Oncol 21:180–183PubMedGoogle Scholar
  6. 6.
    Ben-Arie A, Goldchmit C, Laviv Y et al (2004) The malignant potential of endometrial polyps. Eur J Obstet Gynecol Reprod Biol 115:206–210PubMedCrossRefGoogle Scholar
  7. 7.
    Emons G, Huschmand-Nia A, Krauss T, Hinney B (2004) Hormone replacement therapy and endometrial cancer. Onkologie 27:207–210PubMedCrossRefGoogle Scholar
  8. 8.
    Smith DC, Prentice R, Thompson DJ, Herrmann WL (1975) Association of exogenous estrogen and endometrial carcinoma. N Engl J Med 293:1164–1167PubMedCrossRefGoogle Scholar
  9. 9.
    Cuzick J, Powles T, Veronesi U et al (2003) Overview of the main outcomes in breast-cancer prevention trials. Lancet 361:296–300PubMedCrossRefGoogle Scholar
  10. 10.
    Niederacher D, An HX, Camrath S et al (1998) Loss of heterozygosity of BRCA1, TP53 and TCRD markers analysed in sporadic endometrial cancer. Eur J Cancer 34:1770–1776PubMedCrossRefGoogle Scholar
  11. 11.
    Chen EH, Olson EN (2005) Unveiling the mechanisms of cell–cell fusion. Science 308:369–373PubMedCrossRefGoogle Scholar
  12. 12.
    Ogle BM, Cascalho M, Platt JL (2005) Biological implications of cell fusion. Nat Rev Mol Cell Biol 6:567–575PubMedCrossRefGoogle Scholar
  13. 13.
    Potgens AJ, Schmitz U, Bose P, Versmold A, Kaufmann P, Frank HG (2002) Mechanisms of syncytial fusion: a review. Placenta 23:S107–S113PubMedCrossRefGoogle Scholar
  14. 14.
    Bradley CS, Benjamin I, Wheeler JE, Rubin SC (1998) Endometrial adenocarcinoma with trophoblastic differentiation. Gynecol Oncol 69:74–77PubMedCrossRefGoogle Scholar
  15. 15.
    Bannert N, Kurth R (2004) Retroelements and the human genome: new perspectives on an old relation. Proc Natl Acad Sci USA 101:14572–14579PubMedCrossRefGoogle Scholar
  16. 16.
    Benit L, Dessen P, Heidmann T (2001) Identification, phylogeny, and evolution of retroviral elements based on their envelope genes. J Virol 75:11709–11719PubMedCrossRefGoogle Scholar
  17. 17.
    Mallet F, Bouton O, Prudhomme S et al (2004) The endogenous retroviral locus ERVWE1 is a bona fide gene involved in hominoid placental physiology. Proc Natl Acad Sci USA 101:1731–1736PubMedCrossRefGoogle Scholar
  18. 18.
    Yu C, Shen K, Lin M et al (2002) GCMa regulates the Syncytin-mediated trophoblastic fusion. J Biol Chem 277:50062–50068PubMedCrossRefGoogle Scholar
  19. 19.
    Hashemolhosseini S, Wegner M (2004) Impacts of a new transcription factor family: mammalian GCM proteins in health and disease. J Cell Biol 166:765–768PubMedCrossRefGoogle Scholar
  20. 20.
    Matouskova M, Blazkova J, Pajer P, Pavlicek A, Hejnar J (2006) CpG methylation suppresses transcriptional activity of human syncytin-1 in non-placental tissues. Exp Cell Res 312:1011–1020PubMedCrossRefGoogle Scholar
  21. 21.
    Cheynet V, Ruggieri A, Oriol G et al (2005) Synthesis, assembly, and processing of the Env ERVWE1/Syncytin human endogenous retroviral envelope. J Virol 79:5585–5593PubMedCrossRefGoogle Scholar
  22. 22.
    Mi S, Lee X, Li X et al (2000) Syncytin is a captive retroviral envelope protein involved in human placental morphogenesis. Nature 403:785–789PubMedCrossRefGoogle Scholar
  23. 23.
    Johnston ER, Radke K (2000) The SU and TM envelope protein subunits of bovine leukemia virus are linked by disulfide bonds, both in cells and in virions. J Virol 74:2930–2935PubMedCrossRefGoogle Scholar
  24. 24.
    Lavillette D, Marin M, Ruggieri A, Mallet F, Cosset FL, Kabat D (2002) The envelope glycoprotein of human endogenous retrovirus type W uses a divergent family of amino acid transporters/cell surface receptors. J Virol 76:6442–6452PubMedCrossRefGoogle Scholar
  25. 25.
    Sommerfelt MA, Williams BP, McKnight A, Goodfellow PN, Weiss RA (1990) Localization of the receptor gene for type D simian retroviruses on human chromosome 19. J Virol 64:6214–6220PubMedGoogle Scholar
  26. 26.
    Derynck R, Zhang YE (2003) Smad-dependent and Smad-independent pathways in TGF-beta family signalling. Nature 425:577–584PubMedCrossRefGoogle Scholar
  27. 27.
    Gold LI (1999) The role for transforming growth factor-beta (TGF-beta) in human cancer. Crit Rev Oncog 10:303–360PubMedGoogle Scholar
  28. 28.
    Parekh TV, Gama P, Wen X et al (2002) Transforming growth factor beta signaling is disabled early in human endometrial carcinogenesis concomitant with loss of growth inhibition. Cancer Res 62:2778–2790PubMedGoogle Scholar
  29. 29.
    Dowdy SC, Mariani A, Reinholz MM et al (2005) Overexpression of the TGF-beta antagonist Smad7 in endometrial cancer. Gynecol Oncol 96:368–373PubMedCrossRefGoogle Scholar
  30. 30.
    Yang NN, Venugopalan M, Hardikar S, Glasebrook A (1996) Identification of an estrogen response element activated by metabolites of 17beta-estradiol and raloxifene. Science 273:1222–1225PubMedCrossRefGoogle Scholar
  31. 31.
    Arici A, MacDonald PC, Casey ML (1996) Modulation of the levels of transforming growth factor beta messenger ribonucleic acids in human endometrial stromal cells. Biol Reprod 54:463–469PubMedCrossRefGoogle Scholar
  32. 32.
    Strick R, Strissel PL, Gavrilov K, Levi-Setti R (2001) Cation–chromatin binding as shown by ion microscopy is essential for the structural integrity of chromosomes. J Cell Biol 155:899–910PubMedCrossRefGoogle Scholar
  33. 33.
    Fearon ER, Vogelstein B (1990) A genetic model for colorectal tumorigenesis. Cell 61:759–767PubMedCrossRefGoogle Scholar
  34. 34.
    Beckmann MW, Niederacher D, Bender HG (1998) Mechanisms of steroid hormone action and resistance in endometrial and breast cancer. Eur J Cancer Prev 7:S25–S28PubMedCrossRefGoogle Scholar
  35. 35.
    Lalloo F, Evans G (2001) Molecular genetics and endometrial cancer. Best Pract Res Clin Obstet Gynaecol 15:355–363PubMedCrossRefGoogle Scholar
  36. 36.
    Sasaki M, Dharia A, Oh BR, Tanaka Y, Fujimoto S, Dahiya R (2001) Progesterone receptor B gene inactivation and CpG hypermethylation in human uterine endometrial cancer. Cancer Res 61:97–102PubMedGoogle Scholar
  37. 37.
    Berstein LM, Tchernobrovkina AE, Gamajunova VB et al (2003) Tumor estrogen content and clinico-morphological and endocrine features of endometrial cancer. J Cancer Res Clin Oncol 129:245–249PubMedGoogle Scholar
  38. 38.
    Palmarini M, Mura M, Spencer TE (2004) Endogenous betaretroviruses of sheep: teaching new lessons in retroviral interference and adaptation. J Gen Virol 85:1–13PubMedCrossRefGoogle Scholar
  39. 39.
    Wang-Johanning F, Frost AR, Johanning GL et al (2001) Expression of human endogenous retrovirus k envelope transcripts in human breast cancer. Clin Cancer Res 7:1553–1560PubMedGoogle Scholar
  40. 40.
    Menendez L, Benigno BB, McDonald JF (2004) L1 and HERV-W retrotransposons are hypomethylated in human ovarian carcinomas. Mol Cancer 3:12PubMedCrossRefGoogle Scholar
  41. 41.
    Berzal Cantalejo F, Sabater Marco V, Alonso Hernandez S, Jimenez Pena R, Martorell Cebollada MA (2004) Syncytial giant cell component. Review of 55 renal cell carcinomas. Histol Histopathol 19:113–118PubMedGoogle Scholar
  42. 42.
    Vicandi B, Jimenez-Heffernan JA, Lopez-Ferrer P et al (2004) Fine needle aspiration cytology of mammary carcinoma with osteoclast-like giant cells. Cytopathology 15:321–325PubMedCrossRefGoogle Scholar
  43. 43.
    Pesce C, Merino MJ, Chambers JT, Nogales F (1991) Endometrial carcinoma with trophoblastic differentiation. An aggressive form of uterine cancer. Cancer 68:1799–1802PubMedCrossRefGoogle Scholar
  44. 44.
    Boyd JA, Kaufman DG (1990) Expression of transforming growth factor beta 1 by human endometrial carcinoma cell lines: inverse correlation with effects on growth rate and morphology. Cancer Res 50:3394–3399PubMedGoogle Scholar
  45. 45.
    Florini JR, Roberts AB, Ewton DZ, Falen SL, Flanders KC, Sporn MB (1986) Transforming growth factor-beta. A very potent inhibitor of myoblast differentiation, identical to the differentiation inhibitor secreted by Buffalo rat liver cells. J Biol Chem 261:16509–16513PubMedGoogle Scholar
  46. 46.
    Karsdal MA, Hjorth P, Henriksen K et al (2003) Transforming growth factor-beta controls human osteoclastogenesis through the p38 MAPK and regulation of RANK expression. J Biol Chem 278:44975–44987PubMedCrossRefGoogle Scholar
  47. 47.
    Lafyatis R, Lechleider R, Roberts AB, Sporn MB (1991) Secretion and transcriptional regulation of transforming growth factor-beta 3 during myogenesis. Mol Cell Biol 11:3795–3803PubMedGoogle Scholar
  48. 48.
    Panousis CG, Evans G, Zuckerman SH (2001) TGF-beta increases cholesterol efflux and ABC-1 expression in macrophage-derived foam cells: opposing the effects of IFN-gamma. J Lipid Res 42:856–863PubMedGoogle Scholar
  49. 49.
    Niyogi K, Hildreth JE (2001) Characterization of new syncytium-inhibiting monoclonal antibodies implicates lipid rafts in human T-cell leukemia virus type 1 syncytium formation. J Virol 75:7351–7361PubMedCrossRefGoogle Scholar
  50. 50.
    Alvarez-Dolado M, Pardal R, Garcia-Verdugo JM et al (2003) Fusion of bone-marrow-derived cells with Purkinje neurons, cardiomyocytes and hepatocytes. Nature 425:968–973PubMedCrossRefGoogle Scholar
  51. 51.
    Kerbel RS, Lagarde AE, Dennis JW, Donaghue TP (1983) Spontaneous fusion in vivo between normal host and tumor cells: possible contribution to tumor progression and metastasis studied with a lectin-resistant mutant tumor. Mol Cell Biol 3:523–538PubMedGoogle Scholar
  52. 52.
    Duelli DM, Hearn S, Myers MP, Lazebnik Y (2005) A primate virus generates transformed human cells by fusion. J Cell Biol 171:493–503PubMedCrossRefGoogle Scholar
  53. 53.
    Mangeney M, Heidmann T (1998) Tumor cells expressing a retroviral envelope escape immune rejection in vivo. Proc Natl Acad Sci USA 95:14920–14925PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Reiner Strick
    • 1
    Email author
  • Sven Ackermann
    • 1
  • Manuela Langbein
    • 1
  • Justine Swiatek
    • 1
  • Steffen W. Schubert
    • 2
  • Said Hashemolhosseini
    • 2
  • Thomas Koscheck
    • 3
  • Peter A. Fasching
    • 1
  • Ralf L. Schild
    • 1
  • Matthias W. Beckmann
    • 1
  • Pamela L. Strissel
    • 1
  1. 1.Department of Gynaecology and Obstetrics, Laboratory for Molecular MedicineUniversity Clinic ErlangenErlangenGermany
  2. 2.Institute for BiochemistryUniversity of Erlangen-NurembergErlangenGermany
  3. 3.Institute for PathologyUniversity of Erlangen-NurembergErlangenGermany

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