Figure 2.

Oxaliplatin accumulation and cytotoxicity in HEK293 cells stably transfected to overexpress MRP2 (HEK-MRP2 cells) compared to control cells (HEK-P cells). (A) MRP2 was localised to the plasma membranes of HEK-MRP2 cells as demonstrated by MRP2-immunofluorescence confocal microscopy. Red staining, MRP2; Blue staining, DAPI. (B) Representative inhibition of growth of HEK-MRP2 and HEK-P cells after 2-hour exposure to oxaliplatin. Symbols are means and standard errors of the mean [n = 4]. Solid lines are non-linear regression fits (Y = Bottom + (Top − Bottom)/(1 + 10^{((LogIC50 − X)*HillSlope))}) to the data (r² > 0.97). (C) Time-course of platinum accumulation during exposure to oxaliplatin for up to two hours showing lower accumulation of platinum in HEK-MRP2 cells. Asterisks are P values (***P < 0.001; ****P < 0.0001) for differences at each time point from Bonferroni post-tests that followed a Two-way ANOVA [n = 6]. (D) Kinetics of platinum accumulation during exposure to oxaliplatin for up to two hours showing a plateau in levels after one-hour exposure. Solid lines represent non-linear regression fits (y = ymax(1− e^−kx) to the data (r² > 0.92). (E,F) Effect of myricetin (60 μM) on oxaliplatin accumulation [n = 3] (E) and cytotoxicity [n = 3–4] (F). Asterisks are P values (***P < 0.001; ****P < 0.0001) for differences with each of the other three groups from Bonferroni post-tests that followed a Two-way ANOVA. Bars represent means and standard errors of the mean. HEK-MRP2 cells accumulated less platinum and were less sensitive to oxaliplatin-induced growth inhibition than control HEK-P cells. Myricetin increased the accumulation and cytotoxicity of oxaliplatin in HEK-MRP2 cells but not in HEK-P cells.