Decreased expression of cyclin G2 is significantly linked to the malignant transformation of papillary carcinoma of the thyroid.
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.
Ito
Yasuhiro
Y
Department of Surgery, Kuma Hospital, 8-2-35, Shimoyamate-dori, Chuo-ku, Kobe 650-0011, Japan. ito01@kuma-h.or.jp
Yoshida
Hiroshi
H
Uruno
Takashi
T
Nakano
Keiichi
K
Takamura
Yuuki
Y
Miya
Akihiro
A
Kobayashi
Kaoru
K
Yokozawa
Tamotsu
T
Matsuzuka
Fumio
F
Kuma
Kanji
K
Miyauchi
Akira
A
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
C101593:CCNG2 protein, human; D056767:Cyclin G2; D016213:Cyclins