title: Decreased orotate phosphoribosyltransferase activity produces 5-fluorouracil resistance in a human gastric cancer cell line.
abstract: To elucidate the mechanism of resistance to 5-fluorouracil (5-FU) in human gastric cancer cells, we established a cell line MKN45/F2R, which acquired 5-FU resistance as a result of continuous exposure to increasing dosages of 5-FU over a year. The cell line showed 157-fold elevated 5-FU resistance compared to the MKN45 human gastric cancer parental cell line. Furthermore, the cells acquired crossresistance to paclitaxel and docetaxel. To identify the mechanism of 5-FU resistance, the expressions of 5-FU metabolic enzymes were examined. Although protein expression and activity of thymidylate synthase and dihydropyrimidine dehydrogenase did not change, orotate phosphoribosyl-transferase (OPRT) protein expression and activity significantly decreased in the 5-FU resistant MKN45/F2R cells. Interestingly, expression of proteins related to taxane resistance including P-glycoprotein, class III beta-tubulin and Bcl-2 increased in MKN45/F2R cells. OPRT-knockout MKN45 parent cells using small interfering RNA demonstrated 15.8-fold increased resistance to 5-FU compared to the control cells. However, resistance to paclitaxel and docetaxel was not observed. These results strongly indicate that decreased activity of OPRT plays an important role in the acquired resistance of gastric cancer cells towards 5-FU; however, it does not play a direct role in paclitaxel and docetaxel resistance. Further studies are now underway to identify genes related to crossresistance to these chemotherapeutic agents.
authors.affiliation: Department of Surgical Oncology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Tsutani
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yoshida
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sanada
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Wada
authors.forename: Kazuo
authors.initials: K
authors.lastname: Konishi
authors.forename: Masakazu
authors.initials: M
authors.lastname: Fukushima
authors.forename: Morihito
authors.initials: M
authors.lastname: Okada
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D000077143:Docetaxel; D019008:Drug Resistance, Neoplasm; D005472:Fluorouracil / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009962:Orotate Phosphoribosyltransferase / Q000096:biosynthesis*; D017239:Paclitaxel / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000378:metabolism*; D043823:Taxoids / Q000494:pharmacology; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D034741:RNA, Small Interfering; D043823:Taxoids; D013778:Tetrazolium Salts; D013844:Thiazoles; D000077143:Docetaxel; D009962:Orotate Phosphoribosyltransferase; C022616:thiazolyl blue; D017239:Paclitaxel; D005472:Fluorouracil