title: The cancer/testis-antigen PRAME supports the pluripotency network and represses somatic and germ cell differentiation programs in seminomas.
abstract: Cancer/testis-antigens (CTAs) are specifically expressed in human malignancies and testis tissue, but their molecular functions are poorly understood. CTAs serve as regulators of gene expression, cell cycle and spermatogenesis, as well as targets for immune-based therapies. The CTA PRAME is expressed in various cancers, antagonises retinoic acid signalling and is regulated by DNA methylation and histone acetylation.
  
  
  
  We analysed the molecular function of the CTA PRAME in primordial germ cells (PGC) and testicular germ cell cancers (GCC). GCCs arise from a common precursor lesion termed germ cell neoplasia in situ (GCNIS), which itself is thought to originate from a defective PGC. GCNIS cells eventually develop into unipotent seminomas or totipotent embryonal carcinomas (ECs), which are capable of differentiation into teratomas, yolk-sac tumours and choriocarcinomas.
  
  
  
  PRAME is, like the master regulator of PGCs SOX17 expressed in human PGCs, GCNIS and seminomas but absent in ECs. shRNA-mediated knockdown of PRAME in seminomatous TCam-2 cells left SOX17 levels unchanged, but resulted in downregulation of pluripotency- and PGC-related genes (LIN28, PRDM14, ZSCAN10), whereas somatic and germ cell differentiation markers were upregulated. So, PRAME seems to act downstream of SOX17 by mediating the regulation of the germ cell differentiation and pluripotency programme. Endoderm differentiation is triggered in somatic cells by SOX17, suggesting that in PGCs, PRAME represses this programme and modulates SOX17 to function as a PGC-master regulator. Surprisingly, knockdown of PRAME in TCam-2 cells did not render the cells sensitive towards retinoic acid, despite the fact that PRAME has been described to antagonise retinoic acid signalling. Finally, we demonstrate that in non-seminomas PRAME expression is silenced by DNA methylation, which can be activated by formation of euchromatin via histone-deacetylase-inhibitors.
  
  
  
  We identified the CTA PRAME as a downstream factor of SOX17 and LIN28 in regulating pluripotency and suppressing somatic/germ cell differentiation in PGC, GCNIS and seminomas.
authors.affiliation: Department of Developmental Pathology, Institute of Pathology, University of Bonn Medical School, 53127 Bonn, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Nettersheim
authors.affiliation: Department of Developmental Pathology, Institute of Pathology, University of Bonn Medical School, 53127 Bonn, Germany.
authors.forename: Isabell
authors.initials: I
authors.lastname: Arndt
authors.affiliation: Department of Developmental Pathology, Institute of Pathology, University of Bonn Medical School, 53127 Bonn, Germany.
authors.forename: Rakesh
authors.initials: R
authors.lastname: Sharma
authors.affiliation: Institute of Clinical Chemistry and Clinical Pharmacology, University of Bonn Medical School, 53127 Bonn, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Riesenberg
authors.affiliation: Department of Developmental Pathology, Institute of Pathology, University of Bonn Medical School, 53127 Bonn, Germany.
authors.forename: Sina
authors.initials: S
authors.lastname: Jostes
authors.affiliation: Department of Developmental Pathology, Institute of Pathology, University of Bonn Medical School, 53127 Bonn, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Schneider
authors.affiliation: Institute of Clinical Chemistry and Clinical Pharmacology, University of Bonn Medical School, 53127 Bonn, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Hölzel
authors.affiliation: Institute of Pathology, University of Bonn Medical School, 53127 Bonn, Germany.
authors.forename: Glen
authors.initials: G
authors.lastname: Kristiansen
authors.affiliation: Department of Developmental Pathology, Institute of Pathology, University of Bonn Medical School, 53127 Bonn, Germany.
authors.forename: Hubert
authors.initials: H
authors.lastname: Schorle
mesh_terms: D000951:Antigens, Neoplasm / Q000235:genetics* / Q000378:metabolism; D015153:Blotting, Western; D002454:Cell Differentiation / Q000235:genetics*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D055785:Gene Knockdown Techniques; D005854:Germ Cells / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism*; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D018239:Seminoma / Q000235:genetics* / Q000378:metabolism; D013736:Testicular Neoplasms / Q000235:genetics* / Q000378:metabolism; D013737:Testis / Q000378:metabolism*
chemical_list: D000951:Antigens, Neoplasm; C404944:PRAME protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering