Figure 4.

ABCB1 expression levels in the docetaxel-resistant cell lines. (a) ABCB1 expression on total protein cellular extracts was assessed by nanocapillary electrophoresis using β-actin expression as normalization factor. (b) ABCB1 expression was also investigated by immunocytochemistry, showing expression in docetaxel-resistant cells and a strong membrane presence. (c) Representative images of Rhodamine 123 accumulation in C4-2B^R cells, untreated or after blockage of ABCB1 function with PSC833. Magnification, 10×. (d,e) Blocking ABCB1 with PSC833 reverts resistance to docetaxel. Cells were treated for 48 h with vehicle, PSC833 alone, docetaxel alone, or a combination of 20 nM docetaxel and increasing doses of PSC833, showing that the resistance phenotype was dependent on ABCB1 function. (f) Flow cytometric analyses of cell cycle progression of C4-2B^R and LNCaP^R resistant cells treated with 20 nM of docetaxel alone or in combination with 1 μM PSC833 for 24 h. Cells were harvested, fixed, and stained with PI for fluorescence-activated cell sorter analysis. Data were analyzed using FlowJo Software.