title: Overexpression of TET dioxygenases in seminomas associates with low levels of DNA methylation and hydroxymethylation.
abstract: Germ cell tumors and particularly seminomas reflect the epigenomic features of their parental primordial germ cells (PGCs), including genomic DNA hypomethylation and expression of pluripotent cell markers. Because the DNA hypomethylation might be a result of TET dioxygenase activity, we examined expression of TET1-3 enzymes and the level of their product, 5-hydroxymethylcytosine (5hmC), in a panel of histologically characterized seminomas and non-seminomatous germ cell tumors. Expression of TET dioxygenase mRNAs was quantified by real-time PCR. TET1 expression and the level of 5hmC were examined immunohistochemically. Quantitative assessment of 5-methylcytosine (5mC) and 5hmC levels was done by the liquid chromatography-mass spectroscopy technique. We found highly increased expression of TET1 dioxygenase in most seminomas and strong TET1 staining in seminoma cells. Isocitrate dehydrogenase 1 and 2 mutations were not detected, suggesting the enzymatic activity of TET1. The levels of 5mC and 5hmC in seminomas were found decreased in comparison to non-seminomatous germ cell tumors and healthy testicular tissue. We propose that TET1 expression should be studied as a potential marker of seminomas and mixed germ cell tumors and we suggest that elevated expression of TET dioxygenase enzymes is associated with the maintenance of low DNA methylation levels in seminomas. This "anti-methylator" phenotype of seminomas is in contrast to the CpG island methylator phenotype (CIMP) observed in a fraction of tumors of various types.
authors.affiliation: Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Videnska 1083, CZ-14220 Prague 4, Czech Republic.
authors.forename: Martina
authors.initials: M
authors.lastname: Benešová
authors.affiliation: Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Videnska 1083, CZ-14220 Prague 4, Czech Republic.
authors.forename: Kateřina
authors.initials: K
authors.lastname: Trejbalová
authors.affiliation: Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Videnska 1083, CZ-14220 Prague 4, Czech Republic.
authors.forename: Dana
authors.initials: D
authors.lastname: Kučerová
authors.affiliation: Department of Pathology, Third Faculty of Medicine, Charles University in Prague, Ruska 87, CZ-10000, Prague 10, Czech Republic.
authors.forename: Zdenka
authors.initials: Z
authors.lastname: Vernerová
authors.affiliation: Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Videnska 1083, CZ-14220 Prague 4, Czech Republic.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Hron
authors.affiliation: Department of Pathology, Third Faculty of Medicine, Charles University in Prague, Ruska 87, CZ-10000, Prague 10, Czech Republic.
authors.forename: Arpád
authors.initials: A
authors.lastname: Szabó
authors.affiliation: MRC London Institute of Medical Sciences, London, UK and Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, UK.
authors.forename: Rachel
authors.initials: R
authors.lastname: Amouroux
authors.affiliation: Department of Urology, Third Faculty of Medicine, Charles University in Prague, Ruska 87, CZ-10000, Prague 10, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Klézl
authors.affiliation: MRC London Institute of Medical Sciences, London, UK and Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, UK.
authors.forename: Petra
authors.initials: P
authors.lastname: Hajkova
authors.affiliation: Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Videnska 1083, CZ-14220 Prague 4, Czech Republic.
authors.forename: Jiří
authors.initials: J
authors.lastname: Hejnar
mesh_terms: D044503:5-Methylcytosine / Q000031:analogs & derivatives / Q000032:analysis; D000328:Adult; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics*; D049308:Dioxygenases / Q000032:analysis / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D006899:Mixed Function Oxygenases / Q000032:analysis / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000235:genetics*; D018239:Seminoma / Q000235:genetics* / Q000473:pathology; D013736:Testicular Neoplasms / Q000235:genetics* / Q000473:pathology; D013737:Testis / Q000378:metabolism / Q000473:pathology*; D015854:Up-Regulation
chemical_list: D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; C011865:5-hydroxymethylcytosine; D044503:5-Methylcytosine; D006899:Mixed Function Oxygenases; C462539:TET1 protein, human; C578792:TET3 protein, human; D049308:Dioxygenases; C541081:TET2 protein, human
keywords: 5-hydroxymethylcytosine; 5-methylcytosine; TET1; germ cell tumor; seminoma