title: Overexpression of the orotate phosphoribosyl-transferase gene enhances the effect of 5-fluorouracil on gastric cancer cell lines.
abstract: OBJECTIVE
  Orotate phosphoribosyl-transferase (OPRT) is the initial enzyme of the 5-fluorouracil (5-FU) metabolic pathway, converting 5-FU into 5-fluorouridinemonophosphate, which is the most important mechanism of 5-FU activation. We therefore investigated whether overexpression of the OPRT gene enhances sensitivity to 5-FU.
  
  
  METHODS
  An expression vector of the OPRT gene (pTARGET-OPRT) was transfected into two gastric cancer cell lines, TMK-1 and MKN-45, with low baseline expression levels of OPRT. The sensitivity to and anti-tumor activity of 5-FU were then investigated in vitro and in vivo in these two transfected clones (TMK-OPRT and MKN-OPRT).
  
  
  RESULTS
  Although cell growth was unaltered compared to parent cells, overexpression of the OPRT gene was confirmed by Western blotting in both the TMK-OPRT and MKN-OPRT cells. OPRT enzyme activity increased 38-fold in TMK-OPRT cells and 8.0 fold in MKN-OPRT cells compared to their parent cells. Interestingly, although the sensitivity to Adriamycin, cis-platinum, mitomycin C and paclitaxel was unaltered in the transfected clones, the sensitivity to 5-FU was increased 14.2- and 6.0-fold in TMK-OPRT and MKN-OPRT cells, respectively, compared to their parent cells. Moreover, enhanced sensitivity was also confirmed in the in vivo study.
  
  
  CONCLUSIONS
  The results indicate that overexpression of the OPRT gene plays an important role in the antiproliferative effect of 5-FU and might therefore be a predictive factor of response to 5-FU in gastric cancer patients.
authors.affiliation: Department of Surgical Oncology, Research Institute for Radiation Biology and Medicine, Graduate School of Medical Science, Hiroshima University, Hiroshima, Japan.
authors.forename: Jyunnya
authors.initials: J
authors.lastname: Taomoto
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yoshida
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Wada
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Tanabe
authors.forename: Kazuo
authors.initials: K
authors.lastname: Konishi
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Tahara
authors.forename: Masakazu
authors.initials: M
authors.lastname: Fukushima
mesh_terms: D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000378:metabolism* / Q000494:pharmacology*; D015153:Blotting, Western; D002277:Carcinoma / Q000188:drug therapy / Q000201:enzymology*; D045744:Cell Line, Tumor; D018076:DNA, Complementary / Q000378:metabolism; D005472:Fluorouracil / Q000378:metabolism* / Q000494:pharmacology*; D051379:Mice; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D009962:Orotate Phosphoribosyltransferase / Q000235:genetics / Q000378:metabolism*; D009964:Orotidine-5'-Phosphate Decarboxylase / Q000235:genetics / Q000378:metabolism*; D013274:Stomach Neoplasms / Q000188:drug therapy / Q000201:enzymology*; D015854:Up-Regulation; D023041:Xenograft Model Antitumor Assays
chemical_list: D000964:Antimetabolites, Antineoplastic; D018076:DNA, Complementary; D009097:Multienzyme Complexes; C027157:uridine 5'-monophosphate synthase; D009962:Orotate Phosphoribosyltransferase; D009964:Orotidine-5'-Phosphate Decarboxylase; D005472:Fluorouracil