title: Doxorubicin sensitizes human bladder carcinoma cells to Fas-mediated cytotoxicity.
abstract: BACKGROUND
  The resistance of bladder carcinoma to anticancer chemotherapeutic agents remains a major problem. Hence, several immunotherapeutic approaches have been developed to treat the drug-resistant cancer cells. Fas antigen (Fas) and Fas ligand participate in cytotoxicity mediated by T lymphocytes and natural killer cells. Like Fas ligand, anti-Fas monoclonal antibody (MoAb) induces apoptosis of the cells expressing Fas. This study examined whether bladder carcinoma cells are sensitive to cytotoxicity mediated by anti-Fas MoAb and whether anticancer agents synergize with anti-Fas MoAb in cytotoxicity.
  
  
  METHODS
  Cytotoxicity was determined by a 1-day microculture tetrazolium dye assay. Synergy was assessed by isobolographic analysis.
  
  
  RESULTS
  The T24 human bladder carcinoma cell line constitutively expressed the Fas on the cell surface; however, T24 line was resistant to anti-Fas MoAb. Treatment of T24 cells with anti-Fas MoAb in combination with mitomycin C, methotrexate, or 5-fluorouracil did not overcome their resistance to these agents. However, treatment of T24 cells with a combination of anti-Fas MoAb and doxorubicin resulted in a synergistic cytotoxic effect. In addition, the doxorubicin-resistant T24 cells were sensitive to treatment with a combination of anti-Fas MoAb and doxorubicin. Synergy was also achieved in three other bladder carcinoma cell lines and four freshly derived human bladder carcinoma cells. Treatment with anti-Fas MoAb in combination with epirubicin or pirarubicin also resulted in a synergistic cytotoxic effect on T24 cells. The mechanisms of synergy were examined. Anti-Fas MoAb did not affect the intracellular accumulation of doxorubicin, the expression of P-glycoprotein, or the expression of the antioxidant glutathione S-transferase-pi mRNA. However, treatment with doxorubicin enhanced the expression of Fas on T24 cells.
  
  
  CONCLUSIONS
  This study demonstrated that treatment of bladder carcinoma cells with doxorubicin sensitized the cells to lysis by anti-Fas MoAb. The synergistic effect obtained with established doxorubicin-resistant bladder carcinoma cells and freshly isolated bladder carcinoma cells suggests that drug-resistant bladder carcinoma cells can be sensitized by doxorubicin to Fas- and Fas ligant-mediated cytotoxicity by lymphocytes. Furthermore, the sensitization required low concentrations of doxorubicin, thus supporting the in vivo application of a combination of chemotherapy and immunotherapy in the treatment of drug-resistant and/or immunotherapy-resistant bladder carcinoma.
authors.affiliation: Department of Urology, Faculty of Medicine, Kyoto University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Mizutani
authors.forename: Y
authors.initials: Y
authors.lastname: Okada
authors.forename: O
authors.initials: O
authors.lastname: Yoshida
authors.forename: M
authors.initials: M
authors.lastname: Fukumoto
authors.forename: B
authors.initials: B
authors.lastname: Bonavida
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000627:therapeutic use*; D000911:Antibodies, Monoclonal / Q000494:pharmacology / Q000627:therapeutic use*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D004317:Doxorubicin / Q000627:therapeutic use*; D004351:Drug Resistance; D004357:Drug Synergism; D005434:Flow Cytometry; D006801:Humans; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy*; D019014:fas Receptor / Q000276:immunology*
chemical_list: D000903:Antibiotics, Antineoplastic; D000911:Antibodies, Monoclonal; D019014:fas Receptor; D004317:Doxorubicin