Doxorubicin and taxol are known to be exported by the multidrug resistance 1 protein (MDR1) and multidrug resistance-associated proteins, such as MRP1 and MRP2.32 MDR1 is considered to have a minor role for drug resistance in prostate tumor cells.33 On the other hand, MRP family members are expressed in prostate cancer cells,34 and we could detect MRP1 protein in LNCaP and 22Rv1 cells by Western blotting (data not shown). This evidence concerns the gene ABCB1 and prostate cancer.