Increased Replication Stress Sensitises High Risk Neuroblastoma Cells to ATR and PARP Inhibition

Background: Neuroblastoma (NB) is a rare childhood cancer but accounts for 15% of paediatric deaths. MYCN amplification and/or ATM loss through 11q deletion may cause an increase in replication stress (RS) substantial proportion (~80%) high-risk NB. RS creates dependency on ATR-mediated S and G2 checkpoint control. This study aimed to determine if or identifies cells which are sensitive ATR inhibition (ATRi). As PARP causes unrepaired single-strand DNA breaks progressing replication, we also examined the effect ATRi inhibitor (PARPi) cytotoxicity PARPi-induced RS, cell cycle arrest homologous recombination repair (HRR) activity. Methods: Cell proliferation response 72 h treatment with inhibitor, VE-821, was assessed by XTT (Roche) clonogenic survival assays panel 11 NB lines VE-821 growth caused PARPi, Olaparib, 4 lines. CHK1S345 (a marker activity) RPA2S8 H2AXS129 phosphorylation (RS markers) were Western blotting immunofluorescent microscopy. HRR formation RAD51 foci analysis carried out flow cytometry. Results: VE-821-induced death significantly increased MYCN-amplified low protein expression (p < 0.05 Mann–Whitney U test). Olaparib (5 µM) after 24 all prevented reduced Olaparib-induced formation. abrogated arrest. Conclusion: determinants sensitivity sensitises PARPi abrogating S/G2 impairing HRR.