Synergistic Antitumor Effects of Fleroxacin With 5-fluorouracil In Vitro and In Vivo for Bladder Cancer Cell Lines

OBJECTIVES To study the antitumor effects of fleroxacin against bladder tumor cell lines and the synergistic effect with 5-fluorouracil (5-FU) both in vitro and in vivo. METHODS In vitro, the MBT-2 and T-24 urothelial carcinoma cell lines were exposed to fleroxacin in concentrations of 0-800 mu g/mL for 12, 24, and 48 hours. Cytotoxicity was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay. Synergism of fleroxacin with 5-FU was evaluated using the normalized isobologram and combination index by CalcuSyn for Windows computer program. In vivo, 4-week-old female C57BL/6 mice were orally administered fleroxacin and/or 5-FU 1 week before starting administration of a carcinogenic agent (0.05% N-butyl-N-(4-hydroxybutyl) nitrosamine) for 12 weeks. The mice were killed 8 weeks after the end of administration for histologic evaluation of the urinary bladder. RESULTS Fleroxacin significantly inhibited cell proliferation in a dose-and time-dependent manner at concentrations of 50-800 mu g/mL for 12, 24, and 48 hours. The inhibitory effects of fleroxacin combined with 5-FU appeared synergistic using normalized isobologram and combination index analysis. In vivo, no significant changes in bladder tumor frequency were noted between the control and fleroxacin and 5-FU groups. Significant inhibition of tumor frequency was observed only when fleroxacin was administered with 5-FU. CONCLUSIONS Fleroxacin combined with 5-FU inhibited the proliferation of bladder tumor cell lines both in vitro and in vivo. This combination therapy might be applicable in clinical settings. UROLOGY 74: 1370-1376, 2009. (C) 2009 Elsevier Inc.