title: Forced expression of cytidine deaminase confers sensitivity to capecitabine.
abstract: OBJECTIVE
  Cytidine deaminase (CDD) is involved in the metabolism of new pyrimidine analogues, capecitabine (N(4)-pentyloxycarbonyl-5'-deoxy-5-fluorocytidine) and gemcitabine (2',2'-difluorodeoxycytidine). The purpose of the present study was to directly examine the role of CDD in tumor cells themselves in mediating the sensitivity to capecitabine compared with gemcitabine.
  
  
  METHODS
  The human bladder cancer cell line T24 was transfected with human CDD2 cDNA by the lipofectin method.
  
  
  RESULTS
  Transfection of CDD2 cDNA did not change the levels of thymidine phosphorylase, dihydropyrimidine dehydrogenase and thymidylate synthase (TS) but increased the CDD activity significantly (p < 0.01). Forced expression of CDD made T24 sensitive to 5'-deoxy-5-fluorocytidine (5'DFCR) in vitro and capecitabine in vivo, but resistant to gemcitabine both in vitro and in vivo. Tetrahydrouridine, a specific CDD inhibitor, abrogated the changes in the in vitro sensitivity to 5'DFCR and gemcitabine by transfection of CDD2 cDNA. Transfection of CDD2 cDNA resulted in a significant increase in cellular 5-fluorouracil level (p < 0.01) and inhibition of TS activity (p < 0.01) after treatment with 5'DFCR in vitro.
  
  
  CONCLUSIONS
  The present study clearly showed direct evidence for the contribution of CDD in tumor cells themselves to the sensitivities to capecitabine and gemcitabine.
authors.affiliation: Department of Urology, Jichi Medical School, Tochigi, Japan. moritatu@jichi.ac.jp
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Morita
authors.forename: Atsushi
authors.initials: A
authors.lastname: Matsuzaki
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Kurokawa
authors.forename: Akihiko
authors.initials: A
authors.lastname: Tokue
mesh_terms: D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000627:therapeutic use*; D000069287:Capecitabine; D002470:Cell Survival / Q000187:drug effects; D003564:Cytidine Deaminase / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000627:therapeutic use*; D042943:Dihydrouracil Dehydrogenase (NADP) / Q000378:metabolism; D004195:Disease Models, Animal; D004354:Drug Screening Assays, Antitumor; D004797:Enzyme-Linked Immunosorbent Assay; D005472:Fluorouracil / Q000031:analogs & derivatives; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D013939:Thymidine Phosphorylase / Q000378:metabolism; D013940:Thymidylate Synthase / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000637:transplantation; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D023041:Xenograft Model Antitumor Assays; D000093542:Gemcitabine
chemical_list: D000964:Antimetabolites, Antineoplastic; D018076:DNA, Complementary; D003841:Deoxycytidine; D000069287:Capecitabine; C418208:5'-deoxy-5-fluorocytidine; D042943:Dihydrouracil Dehydrogenase (NADP); D013940:Thymidylate Synthase; D013939:Thymidine Phosphorylase; D003564:Cytidine Deaminase; D005472:Fluorouracil; D000093542:Gemcitabine