Fig 4.

Drug efflux in filamin-A proficient and deficient cells. The cells were treated with 1.0 μg/ml of doxorubicin for 10 min, then were fixed with cold 4% paraformaldehyde immediately or after 15 or 30 min incubation in drug-free medium. Fixed cells were stained with DAPI. Images containing red and blue channels were taken with fluorescent microscope. The signal intensities from red channel (doxorubicin) and blue channel (DNA, internal control) were measured with Image J as described before²². The ratio of red signal over blue reflects the intracellular concentration of doxorubicin. Panel A shows the representative images taken after 15 min drug efflux. Panel B shows quantitative data of intracellular concentration of doxorubicin with various time drug excretions (* p<0.05, ** p<0.01). 40 cells were analyzed from each slide and shown are the averages from three independent experiments. Error bars are standard errors. To assess the efflux of etoposide, A7 and M2 cells were treated with 50 μM etoposide for 2 hours, and then the cells were harvested immediately or after 15 or 30 min incubation in drug-free medium. The amount of etoposide in the cells was determined with HPLC (Materials and Methods). Panel C shows the intracellular concentration of etoposide of A7 and M2 cells. Shown are the averages from three independent experiments. Error bars are standard errors.