This Article Free Full Text (Free PDF) Free References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Imai, T. Articles by Hirose, M. Search for Related Content PubMed PubMed Citation Articles by Imai, T. Articles by Hirose, M. Social Bookmarking                   What's this?

Sequential Analysis of Development of Invasive Thyroid Follicular Cell Carcinomas in Inflamed Capsular Regions of Rats Treated with Sulfadimethoxine after N-bis(2-hydroxypropyl)nitrosamine-initiation

Division of Pathology, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-Ku, Tokyo 158-8501, Japan, imai{at}nihs.go.jp

Jun-Ichi Onose

Division of Pathology, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-Ku, Tokyo 158-8501, Japan

Mai Hasumura

Division of Pathology, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-Ku, Tokyo 158-8501, Japan

Makoto Ueda

Division of Pathology, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-Ku, Tokyo 158-8501, Japan

Tamotsu Takizawa

Division of Pathology, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-Ku, Tokyo 158-8501, Japan

Masao Hirose

Division of Pathology, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-Ku, Tokyo 158-8501, Japan

A 2-stage thyroid follicular carcinogenesis model in rats initiated with N-bis(2-hydroxypropyl)nitrosamine (DHPN) is widely used to detect modifying effects of chemicals on thyroid carcinogenesis. A number of goitrogens are known to strongly promote carcinogenesis, and the carcinomas often originate adjacent to the thyroid capsule and show invasive growth into the capsule or adjacent tissues. To clarify mechanisms of progression to invasive carcinomas, we sequentially evaluated histopathological and immunohistochemical characteristics of thyroids in male F344 rats treated with sulfadimethoxine (SDM, 0.1% in drinking water) for 0—10 weeks beginning 1 week after DHPN initiation (2800 mg/kg body weight, single s.c. injection). In DHPN-SDM-treated rats, multiple focal hyperplasias and adenomas developed in thyroid follicular parenchyma at weeks 4 to 6. Apart from the proliferative lesions, capsular thickening with inflammatory cell infiltration, mainly consisting of macrophages, and migration of follicular epithelium into the capsule were also observed. Focal hyperplasias/adenomas adjacent to the capsule progressively developed to invasive carcinomas at weeks 6 to 10. In thyroid parenchyma, malignant lesions were seldom observed. With SDM-treatment alone, although no neoplastic lesions were observed, capsular thickening with inflammation and epithelial migration resulted in intracapsular residual follicles. Intracapsular residual follicular cells as well as invasive and intrathyroidal carcinoma cells generally showed increased cell proliferative activity, coincidental with cytoplasmic/nuclear positivity for β-catenin. These results suggested that β -catenin activation related to capsular inflammation may play a role in development of invasive carcinomas but is insufficient for tumor formation by itself. Whether this is associated with mutations in the β-catenin gene remains to be clarified.

Key Words: Thyroid • follicular cell carcinomas • N-bis(2-hydroxypropyl)nitrosamine • sulfadimethoxine • invasion • inflammation • cell proliferation • β-catenin.

CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?