New quinolones, ofloxacin and levofloxacin, inhibit telomerase activity in transitional cell carcinoma cell lines

It has been demonstrated that some quinolone antibiotics inhibit cell proliferation in vitro. This study showed that ofloxacin and levofloxacin, two well-known new quinolones, had an inhibitory effect on the proliferation of transitional cell carcinoma cell lines at high concentrations (>200 μg/ml). At relatively low concentrations (10–100 μg/ml), however, there was no apparent antiproliferative effect. Despite this, decreased absorbance in the MTT assay was observed at low concentrations and telomerase activity was significantly decreased. These results suggest that the antiproliferative effect of both ofloxacin and levofloxacin may be related to impairment of telomerase activity by some unknown mechanism.