Furosemide reverses multidrug resistance status in bladder cancer cells in vitro.
BACKGROUND
Multidrug resistance (MDR) has a potentially serious influence on cancer treatment and should be taken into consideration in the design and application of therapeutic regimens. It is mediated through the activity of cellular pumps.


OBJECTIVE
To investigate whether furosemide, itself a pump-blocker, reverses MDR in an in vitro model.


METHODS
An MDR bladder cancer cell line (MGH-u 1R) and its parental (drug sensitive) clone were exposed to epirubicin and furosemide, with the concentration of one drug fixed and that of the other serially diluted in a 96-well plate format. Both drugs formed the variable component in separate experiments. After a 1-h exposure, the cells were washed and replenished with fresh medium. To examine the toxicity of epirubicin and furosemide separately and in combination, monotetrazolium-based assays were carried out. Intracellular epirubicin distribution was assessed by confocal microscopy as a second index of resistance status after in vitro exposure.


RESULTS
MGH-u 1R cells incubated with furosemide showed distribution of drug similar to that in the parental cells (MGH-u 1 sensitive). Controls (without furosemide) continued to show a resistant pattern of fluorescence. In cytotoxicity assays furosemide appeared substantially non-toxic. Resistant cells in the toxicity titration experiments showed increased resistance to levels of furosemide over 500 mug/ml. Parental cells were made only marginally more sensitive against increased background toxicity.


CONCLUSIONS
Furosemide is effective in reversing MDR status in bladder cancer cell lines in vitro. It may also have an increment of intrinsic cytotoxicity, but only at higher concentrations. We propose a potential for further investigation of furosemide as an adjunct to chemotherapy for superficial bladder cancer.
Department of Biomedical Sciences, University of Portsmouth, Portsmouth, UK.
A G
AG
Speers
B A
BA
Lwaleed
J M
JM
Featherstone
B J
BJ
Sallis
A J
AJ
Cooper
D000903:Antibiotics, Antineoplastic / Q000493:pharmacokinetics / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D015251:Epirubicin / Q000493:pharmacokinetics / Q000494:pharmacology; D005665:Furosemide / Q000494:pharmacology*; D006801:Humans; D018613:Microscopy, Confocal; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000473:pathology*
D000903:Antibiotics, Antineoplastic; D049994:Sodium Potassium Chloride Symporter Inhibitors; D015251:Epirubicin; D005665:Furosemide