Genistein sensitizes sarcoma cells in vitro and in vivo by enhancing apoptosis and by inhibiting DSB repair pathways

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Abstract
The aim of this work was to investigate the radiosensitization effects of genistein on mice sarcoma cells and the corresponding biological mechanisms in vitro and in vivo . Using the non-toxic dosage of 10 μM genistein, the sensitizer enhancement ratios after exposure to X-rays at 50% cell survival (IC 50 ) was 1.45 for S180 cells. For mice cotreated with genistein and X-rays, the excised tumor tissues had reduced blood vessels and decreased size and volume compared with the control and irradiation-only groups. Moreover, a significant increase in apoptosis was accompanied by upregulation of Bax and downregulation of Bcl-2 in the mitochondria, and lots of cytochrome c being transferred to the cytoplasm. Furthermore, X-rays combined with genistein inhibited the activity of DNA-PKcs, so DNA-injured sites were dominated by Ku70/80, leading to incompleteness of homologous recombination (HR) and non-homologous end-joining (NHEJ) repairs and the eventual occurrence of cell apoptosis. Our study, for the first time, demonstrated that genistein sensitized sarcoma cells to X-rays and that this radiosensitizing effect depended on induction of the mitochondrial apoptosis pathway and inhibition of the double-strand break (DSB) repair pathways.
Funding Information
  • National Natural Science Foundation of China (U1232207)
  • National Natural Science Foundation of China (11505245 and 11305223)
  • Chinese Academy of Sciences (Y562020XB0 and Y460040XB0)
  • Gansu Provincial Funds for Young Scientists (1107RJYA052 and 1010RJZA006)

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