INA-UV treatment is not affected by the expression of multidrug resistant protein. The MTS assay was applied to assess the viability of MRP1 overexpressing multidrug resistant 293/MRP1 cell (open circles) and its drug sensitive parent cell line 293 (close circles) subjected to doxorubicin exposure (A) or to INA-UV treatment (B). A. The cells were exposed to doxorubicin at the indicated concentrations for 72 hours and then subjected to the MTS assay. Data are mean ± S.D. B. The cells were subjected to INA-UV treatment and then subjected to the MTS assay 24 hours post treatment. Data are mean ± S.D of seven measurements.