Abstract
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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Antimetabolites, Antineoplastic / pharmacology
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Biomarkers, Tumor / genetics
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Cell Line, Tumor / drug effects
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Colorectal Neoplasms / drug therapy*
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Colorectal Neoplasms / enzymology
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Colorectal Neoplasms / genetics
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Colorectal Neoplasms / pathology
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Drug Resistance, Neoplasm / drug effects*
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Drug Resistance, Neoplasm / genetics
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Fluorouracil / pharmacology*
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Gene Expression Regulation, Enzymologic / drug effects
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Gene Expression Regulation, Neoplastic / drug effects
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Humans
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Male
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Mice, Nude
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Thymidylate Synthase / genetics*
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Transgenes
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Xenograft Model Antitumor Assays
Substances
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Antimetabolites, Antineoplastic
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Biomarkers, Tumor
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TYMS protein, human
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Thymidylate Synthase
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Fluorouracil
Grants and funding
This study was funded by grants from the Ministry of Health, Labour and Welfare and the Ministry of Education, Science, Sports and Culture of Japan and also partly supported by the Taiho Pharmaceutical Co., Ltd. (SO). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript, except that the in vivo experiments were done in the laboratories of the Taiho Pharmaceutical Co., Ltd. Co-authors RK and JU are employed by Taiho Pharmaceutical Co., Ltd. Taiho Pharmaceutical Co., Ltd. provided support in the form of salaries for authors RK and JU and in vivo experiments were done in the laboratories of the Taiho Pharmaceutical Co., Ltd., but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.