Targeting dna double strand break repair with hyperthermia and dna-pkcs inhibition to enhance the effect of radiation treatment

Simone Di Franco, Matilde Todaro, Bregje Van Oorschot, Giovanna Granata, Giovanna Granata, Hans M. Rodermond, Nicolaas A.P. Franken, Rosemarie Ten Cate, Jan Paul Medema

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)

Abstract

Radiotherapy is based on the induction of lethal DNA damage, primarily DNA double-strand breaks (DSB). Efficient DSB repair via Non-Homologous End Joining or Homologous Recombination can therefore undermine the efficacy of radiotherapy. By suppressing DNA-DSB repair with hyperthermia (HT) and DNA-PKcs inhibitor NU7441 (DNA-PKcsi), we aim to enhance the effect of radiation. The sensitizing effect of HT for 1 hour at 42°C and DNA-PKcsi [1 μM] to radiation treatment was investigated in cervical and breast cancer cells, primary breast cancer sphere cells (BCSCs) enriched for cancer stem cells, and in an in vivo human tumor model. A significant radio-enhancement effect was observed for all cell types when DNA-PKcsi and HT were applied separately, and when both were combined, HT and DNA-PKcsi enhanced radio-sensitivity to an even greater extent. Strikingly, combined treatment resulted in significantly lower survival rates, 2 to 2.5 fold increase in apoptosis, more residual DNA-DSB 6 h post treatment and a G2-phase arrest. In addition, tumor growth analysis in vivo showed significant reduction in tumor growth and elevated caspase-3 activity when radiation was combined with HT and DNA-PKcsi compared to radiation alone. Importantly, no toxic side effects of HT or DNA-PKcsi were found. In conclusion, inhibiting DNA-DSB repair using HT and DNA-PKcsi before radiotherapy leads to enhanced cytotoxicity in cancer cells. This effect was even noticed in the more radio-resistant BCSCs, which are clearly sensitized by combined treatment. Therefore, the addition of HT and DNA-PKcsi to conventional radiotherapy is promising and might contribute to more efficient tumor control and patient outcome.
Original languageEnglish
Pages (from-to)65504-65513
Number of pages10
JournalOncotarget
Volume7
Publication statusPublished - 2016

All Science Journal Classification (ASJC) codes

  • Oncology

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