Differential regulation of radioadaptation by quercetin between human normal and cancer cells

Figures

• 

  Fig. 1. Quercetin enhances radioadaptation in normal MCF10A cells but sensitizes cancer MCF7 cells to radiation. (A–B) Cell viability in MCF10A (A) and MCF7 (B) cells following treatment with quercetin (12.5 μM), low-dose radiation (0.1 Gy) and subsequent high-dose radiation (5 Gy). (C–D) Surviving fractions determined by clonogenic assay for MCF10A (C) and MCF7 (D) cells under the same treatment conditions. Data is shown as mean ± SEM. * p < 0.05, ** p < 0.01.

• 

  Fig. 2. Effects of quercetin on ROS levels and NQO1 mRNA expression in radioadapted MCF10A and MCF7 cells. (A–B) ROS production and NQO1 mRNA expression were measured at 4 h and 24 h after 5 Gy irradiation in MCF10A (A) and MCF7 (B) cells, pre-treated or not with 0.1 Gy and quercetin. Data is shown as mean ± SEM. * p < 0.05, ** p < 0.01.

• 

  Fig. 3. Quercetin upregulates NQO1 protein expression in normal, but not cancer cells. (A–B) NQO1 protein expression levels in MCF10A (A) and MCF7 (B) cells 4 h and 24 h after high-dose irradiation with or without prior LDRT and quercetin treatment. Data is shown as mean ± SEM. * p < 0.05, ** p < 0.01.

• 

  Fig. 4. Quercetin restores NRF2 nuclear translocation in radioadapted MCF10A cells. Representative immunofluorescence images of NRF2 (green) and DAPI (blue) and quantification of the nuclear-to-cytoplasmic NRF2 fluorescence ratio in MCF10A cells 24 h after 5 Gy irradiation with or without prior LDRT and quercetin treatment (Scale bar: 10 μm). Data is shown as mean ± SEM. * p < 0.05, ** p < 0.01.

• 

  Fig. 5. Quercetin attenuates DNA damage and ATM activation in normal but not cancer cells. (A) Immunofluorescence staining and quantification of γ-H2AX foci in MCF10A and MCF7 cells 24 h after high-dose irradiation with or without prior LDRT and quercetin treatment (Scale bar: 10 μm). (B–C) Representative western blots and quantification of phosphorylated ATM (p-ATM) levels in MCF10A (B) and MCF7 (C) cells at 4 h and 24 h after high-dose irradiation with or without prior LDRT and quercetin treatment. Data is shown as mean ± SEM. * p < 0.05, ** p < 0.01.

• 

  Fig. 6. Schematic illustration of the proposed mechanism.