title: 5-Hydroxymethylcytosine discriminates between parathyroid adenoma and carcinoma.
abstract: BACKGROUND
  Primary hyperparathyroidism is characterized by enlarged parathyroid glands due to an adenoma (80-85 %) or multiglandular disease (~15 %) causing hypersecretion of parathyroid hormone (PTH) and generally hypercalcemia. Parathyroid cancer is rare (<1-5 %). The epigenetic mark 5-hydroxymethylcytosine (5hmC) is reduced in various cancers, and this may involve reduced expression of the ten-eleven translocation 1 (TET1) enzyme. Here, we have performed novel experiments to determine the 5hmC level and TET1 protein expression in 43 parathyroid adenomas (PAs) and 17 parathyroid carcinomas (PCs) from patients who had local invasion or metastases and to address a potential growth regulatory role of TET1.
  
  
  RESULTS
  The global 5hmC level was determined by a semi-quantitative DNA immune-dot blot assay in a smaller number of tumors. The global 5hmC level was reduced in nine PCs and 15 PAs compared to four normal tissue samples (p < 0.05), and it was most severely reduced in the PCs. By immunohistochemistry, all 17 PCs stained negatively for 5hmC and TET1 showed negative or variably heterogeneous staining for the majority. All 43 PAs displayed positive 5hmC staining, and a similar aberrant staining pattern of 5hmC and TET1 was seen in about half of the PAs. Western blotting analysis of two PCs and nine PAs showed variable TET1 protein expression levels. A significantly higher tumor weight was associated to PAs displaying a more severe aberrant staining pattern of 5hmC and TET1. Overexpression of TET1 in a colony forming assay inhibited parathyroid tumor cell growth.
  
  
  CONCLUSIONS
  5hmC can discriminate between PAs and PCs. Whether 5hmC represents a novel marker for malignancy warrants further analysis in additional parathyroid tumor cohorts. The results support a growth regulatory role of TET1 in parathyroid tissue.
authors.affiliation: Department of Surgical Sciences, Endocrine Unit, Uppsala University, Uppsala, SE-751 85 Sweden.
authors.forename: Elham
authors.initials: E
authors.lastname: Barazeghi
authors.affiliation: Department of Anatomical Pathology, Royal North Shore Hospital, Pacific Highway, St Leonards, NSW 2065 Australia ; University of Sydney, Sydney, NSW 2006 Australia.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Gill
authors.affiliation: University of Sydney, Sydney, NSW 2006 Australia ; Department of Surgery, Royal North Shore Hospital, Pacific Highway, St Leonards, NSW 2065 Australia.
authors.forename: Stan
authors.initials: S
authors.lastname: Sidhu
authors.affiliation: Department of Surgical Sciences, Endocrine Unit, Uppsala University, Uppsala, SE-751 85 Sweden ; University of Sydney, Sydney, NSW 2006 Australia ; Department of Surgery, Royal North Shore Hospital, Pacific Highway, St Leonards, NSW 2065 Australia.
authors.forename: Olov
authors.initials: O
authors.lastname: Norlén
authors.affiliation: Department of Histopathology, Hammersmith Hospital, Imperial College, London, UK.
authors.forename: Roberto
authors.initials: R
authors.lastname: Dina
authors.affiliation: Endocrine Surgery, Hammersmith Hospital, Imperial College, London, UK.
authors.forename: F Fausto
authors.initials: FF
authors.lastname: Palazzo
authors.affiliation: Department of Surgical Sciences, Endocrine Unit, Uppsala University, Uppsala, SE-751 85 Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Hellman
authors.affiliation: Department of Surgical Sciences, Endocrine Unit, Uppsala University, Uppsala, SE-751 85 Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Stålberg
authors.affiliation: Department of Surgical Sciences, Endocrine Unit, Uppsala University, Uppsala, SE-751 85 Sweden.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Westin
mesh_terms: D044503:5-Methylcytosine / Q000031:analogs & derivatives; D000236:Adenoma / Q000737:chemistry* / Q000201:enzymology; D000293:Adolescent; D000328:Adult; D000368:Aged; D015153:Blotting, Western; D016022:Case-Control Studies; D003596:Cytosine / Q000031:analogs & derivatives* / Q000032:analysis; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D008875:Middle Aged; D006899:Mixed Function Oxygenases; D010280:Parathyroid Glands / Q000737:chemistry / Q000201:enzymology; D010282:Parathyroid Neoplasms / Q000737:chemistry* / Q000201:enzymology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D055815:Young Adult
chemical_list: D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; C011865:5-hydroxymethylcytosine; D044503:5-Methylcytosine; D003596:Cytosine; D006899:Mixed Function Oxygenases; C462539:TET1 protein, human
keywords: 5-hydroxymethylcytosine; 5hmC; Parathyroid cancer; Primary hyperparathyroidism; TET1