Artichoke Polyphenols Sensitize Human Breast Cancer Cells to Chemotherapeutic Drugs via a ROS-Mediated Downregulation of Flap Endonuclease 1

Figure 3

ROS production in MDA-MB231 cells treated with AEs/PTX. (a) Fluorescence microscopy: MDA-MB231 cells treated with PTX (20 nM) alone or AEs/PTX 25 μM and 20 nM, respectively, or GOx (0.2 UI/ml) as a positive control for 24 h. The presence of ROS was detected by DHE fluorescent staining and red fluorescent-stained cells versus total cells were counted using an inverted fluorescence microscope (magnification 20x). (b, b1) Flow cytometry: the mean fluorescence intensity was expressed as stimulation index obtained by ratio between ROS levels released by cells after 2 h of treatment and ROS detection in control cells. Data is the of 3 independent experiments. Indicative fluorescence peaks of ROS production in cells after 2 h of treatment with 25 μM AEs (blue graph), 20 nM PTX (orange graph), and AEs/PTX, respectively, 25 μM and 20 nM (yellow graph) are reported in (b1). (c) Antioxidant effect on cell viability: NAC reduced the synergistic effect of AEs (12.5-25 μM) in PTX (20 nM) treated cells. The cell viability results are the of at least three independent experiments. Significant statistical differences present in NAC plus and minus AE/PTX-treated cells are indicated by asterisks: 12.5 μM AEs+PTX vs. 12.5 μM AEs+PTX+NAC . 25 μM AEs+PTX vs. 25 μM AEs+PTX+NAC .

(a)

(b)

(c)