title: Decreased expression of cyclin G2 is significantly linked to the malignant transformation of papillary carcinoma of the thyroid.
abstract: BACKGROUND
  Cyclin G2 is a novel cyclin negatively regulating the cell cycle progression, contrary to the characteristics of conventional cyclins. However, little is known about the cyclin G2 expression in human carcinomas. We thus investigated cyclin G2 expression in human thyroid neoplasms.
  
  
  METHODS
  We immunohistochemically examined cyclin G2 expression in 40 normal thyroids and 80 thyroid neoplasms.
  
  
  RESULTS
  Normal thyroids expressed cyclin G2 in more than 5% of follicular cells. Of 30 papillary carcinomas including 6 microcarcinoma, cyclin G2 expression was not, or only occasionally, observed in carcinoma cells, indicating its expression decreased in all these cases. On the other hand, in 16 of the 24 follicular adenomas (66.7%) and 5 of the 23 follicular carcinomas (21.7%), cyclin G2 expression was retained (more than 5% of neoplastic cells were positive), and adenomas more frequently (p = 0.0032) retained cyclin G2 expression than carcinomas.
  
  
  CONCLUSIONS
  Our results suggest that lack of cyclin G2 plays an important role in the malignant transformation of papillary carcinoma. Also, it may play an adjuvant role in the transformation of follicular adenoma to carcinoma. This is the first study of the expression of cyclin G2, a novel cyclin having a role opposite to that of conventional cyclins, in human carcinoma.
authors.affiliation: Department of Surgery, Kuma Hospital, 8-2-35, Shimoyamate-dori, Chuo-ku, Kobe 650-0011, Japan. ito01@kuma-h.or.jp
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ito
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yoshida
authors.forename: Takashi
authors.initials: T
authors.lastname: Uruno
authors.forename: Keiichi
authors.initials: K
authors.lastname: Nakano
authors.forename: Yuuki
authors.initials: Y
authors.lastname: Takamura
authors.forename: Akihiro
authors.initials: A
authors.lastname: Miya
authors.forename: Kaoru
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Yokozawa
authors.forename: Fumio
authors.initials: F
authors.lastname: Matsuzuka
authors.forename: Kanji
authors.initials: K
authors.lastname: Kuma
authors.forename: Akira
authors.initials: A
authors.lastname: Miyauchi
mesh_terms: D002277:Carcinoma / Q000378:metabolism / Q000473:pathology; D002291:Carcinoma, Papillary / Q000378:metabolism* / Q000473:pathology; D018265:Carcinoma, Papillary, Follicular / Q000378:metabolism / Q000473:pathology; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D056767:Cyclin G2; D016213:Cyclins / Q000096:biosynthesis*; D006801:Humans; D013964:Thyroid Neoplasms / Q000378:metabolism* / Q000473:pathology
chemical_list: C101593:CCNG2 protein, human; D056767:Cyclin G2; D016213:Cyclins