title: Expression of thymidylate synthase and orotate phosphoribosyltransferase in thymic carcinoma.
abstract: Thymic carcinoma is a rare thymic epithelial tumor in which chemotherapy for advanced disease has not yet been established. Thymidylate synthase (TS) and orotate phosphoribosyltransferase (OPRT) protein expression levels in thymic carcinoma were evaluated as possible indicators of the anticancer activity of 5-fluorouracil (5-FU) drugs using immunohistochemistry (IHC). A total of 24 samples of thymic carcinoma were used in the present study. The tumor sections were immunohistochemically stained for TS and OPRT. As a comparison with thymic carcinoma, we also assessed the TS and OPRT protein expression levels in 55 lung cancer samples. The TS expression was positive in 12 of 24 thymic carcinoma samples (50%) and OPRT expression was positive in 10 (42%). The association between TS and OPRT expression and Masaoka stages of thymic carcinoma was analyzed. The TS and OPRT expressions in stage IV were significantly higher compared to that in stages I, II or III. We also compared the TS and OPRT expression levels between thymic carcinoma and lung cancer (33 adenocarcinomas and 22 squamous cell carcinomas). TS expression in thymic carcinoma was significantly lower compared with lung squamous cell carcinoma. OPRT expression in thymic carcinoma was significantly higher compared to lung adenocarcinoma. The combination of a relatively low expression of TS and high expression of OPRT suggests an improved antitumor effect of 5-FU drugs in thymic carcinoma compared to in lung carcinoma.
authors.affiliation: Department of Oncology, Immunology and Surgery, Nagoya City University Graduate School of Medical Sciences, Nagoya,  Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Yokota
authors.forename: Hidefumi
authors.initials: H
authors.lastname: Sasaki
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Okuda
authors.forename: Masayuki
authors.initials: M
authors.lastname: Shitara
authors.forename: Yu
authors.initials: Y
authors.lastname: Hikosaka
authors.forename: Satoru
authors.initials: S
authors.lastname: Moriyama
authors.forename: Motoki
authors.initials: M
authors.lastname: Yano
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Fujii