Figure 4: Gemcitabine cytotoxicity assays after pretreatment with probenecid, verapamil or PBS. Pretreatment with probenecid increased gemcitabine cytotoxicity, reaching a significant decrease in AUC values in H1437, H1792 and SU86 cells (p=0.01, 0.03 and 0.01, respectively) and approaching significance in MDA-MB-231 cells (p=0.11). No significant effect was observed with verapamil (p>0.05); statistically significant values are presented (n=4).