Genistein sensitizes glioblastoma cells to carbon ions via inhibiting DNA-PKcs phosphorylation and subsequently repressing NHEJ and delaying HR repair pathways.
Radiother Oncol. 2018 Apr 20. Epub 2018 Apr 20. PMID: 29685705
BACKGROUND AND PURPOSE: Previously, we found genistein could sensitize cancer cells to low linear energy transfer (LET) X-rays via inhibiting DNA-PKcs activities. Especially, high-LET heavy ion produces more DNA double strand breaks (DSBs) than low-LET radiation. Thus, the study was designed to investigate the detailed molecular mechanisms of genistein on sensitizing cancer cells to heavy ions.
MATERIALS AND METHODS: Human glioblastoma (GBM) cell lines with or without genistein pre-treatment were irradiated with high-LET carbon ions. Cell survival was determined with colony formation assay. DNA DSBs were evaluated by means of detectingγ-H2AX foci and immuno-blotting DSB repair proteins, cell apoptosis was detected using Annexin V and PI staining. The interaction of genistein with DNA-PKcs activation site was estimated by molecular docking in the autodock software.
RESULTS: Genistein sensitized DNA-PKcs proficient GBM cells to high-LET carbon ions via delaying the clearance ofγ-H2AX foci. Genistein was physically bound to DNA-PKcs and functionally inhibited the phosphorylation of DNA-PKcs. Consequently, the non-homologous end joining (NHEJ) repair of DSBs was inhibited and the homologous recombination (HR) repair was delayed by genistein, thereby leading to an increasein apoptosis in DNA-PKcs proficient GBM cells after irradiation.
CONCLUSION: Our study demonstrated that genistein holds promise as a radiosensitizer for enhancing the efficacy of carbon ion radiotherapy against DNA-PKcs proficient GBM via inhibiting DNA-PKcs phosphorylation and subsequently repressing NHEJ and delaying HR repair pathways.