Dynamic modulation of thymidylate synthase gene expression and fluorouracil sensitivity in human colorectal cancer cells

• Published in: PloS one 2015-04, Vol.10 (4), p.e0123076
• Main Authors: Wakasa, Kentaro, Kawabata, Rumi, Nakao, Seiki, Hattori, Hiroyoshi, Taguchi, Kenichi, Uchida, Junji, Yamanaka, Takeharu, Maehara, Yoshihiko, Fukushima, Masakazu, Oda, Shinya
• Format: Article
• Language: English
• Subjects: 5-Fluorouracil; Animals; Antimetabolites, Antineoplastic - pharmacology; Apoptosis; Biocompatibility; Biomarkers; Biomarkers, Tumor - genetics; Biosynthesis; Cancer; Cancer genetics; Cancer therapies; Cell Line, Tumor - drug effects; Chemotherapy; Clinical outcomes; Colorectal cancer; Colorectal carcinoma; Colorectal Neoplasms - drug therapy; Colorectal Neoplasms - enzymology; Colorectal Neoplasms - genetics; Colorectal Neoplasms - pathology; Cytotoxicity; Doxycycline; Drug Resistance, Neoplasm - drug effects; Drug Resistance, Neoplasm - genetics; Dynamic range; Enzymes; Fluorouracil; Fluorouracil - pharmacology; Gene expression; Gene Expression Regulation, Enzymologic - drug effects; Gene Expression Regulation, Neoplastic - drug effects; Humans; In vivo methods and tests; Laboratories; Male; Mice, Nude; Pharmaceuticals; Sensitivity; Studies; Thymidylate synthase; Thymidylate Synthase - genetics; Toxicity; Transgenes; Xenograft Model Antitumor Assays; Xenografts
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0123076

Biomarkers have revolutionized cancer chemotherapy. However, many biomarker candidates are still in debate. In addition to clinical studies, a priori experimental approaches are needed. Thymidylate synthase (TS) expression is a long-standing candidate as a biomarker for 5-fluorouracil (5-FU) treatment of cancer patients. Using the Tet-OFF system and a human colorectal cancer cell line, DLD-1, we first constructed an in vitro system in which TS expression is dynamically controllable. Quantitative assays have elucidated that TS expression in the transformant was widely modulated, and that the dynamic range covered 15-fold of the basal level. 5-FU sensitivity of the transformant cells significantly increased in response to downregulated TS expression, although being not examined in the full dynamic range because of the doxycycline toxicity. Intriguingly, our in vitro data suggest that there is a linear relationship between TS expression and the 5-FU sensitivity in cells. Data obtained in a mouse model using transformant xenografts were highly parallel to those obtained in vitro. Thus, our in vitro and in vivo observations suggest that TS expression is a determinant of 5-FU sensitivity in cells, at least in this specific genetic background, and, therefore, support the possibility of TS expression as a biomarker for 5-FU-based cancer chemotherapy.