PGP and urinary bladder carcinoma: Our previous studies (Zhou et al., 2013) have shown that P-gp can also be transferred from the resistant bladder cancer cell line BIU-87/DOX to the sensitive strain BIU-87, which is not resistant to doxorubicin (DOX), providing the first evidence that this ‘non-genetic’ acquired MDR mechanism also exists among bladder cancer cells.