Down regulation of Rab21 decreases epirubicin efflux. (A) Fluorescent microscope images showing intracellular retention of epirubicin after efflux in control and Rab21 siRNA transfected PC-3/Res cells. All images were captured at the same magnification and exposure settings using an Olympus BX-51 fluorescence microscope. Bar, 50µm. (B) Fluorescent intensity of epirubicin was quantified in control and Rab21 siRNA transfected PC-3/Res cells using ImageJ Software. Error bars represent standard error of mean, n=30; ****P ˂ 0.0001.