PARP1 and neuroblastoma: Examination of γH2AX foci and DNA fibre analysis demonstrated that levels of DNA damage and replication fork stalling are also increased by PARP inhibition in the MYCN amplified neuroblastoma cell line IMR-32 (Supplementary Figure 11), suggesting that MYCN expression due to amplification also results in cell death due to effects on DNA fork stability and confirming that the findings in the MYCN ON/OFF expression system are conserved in MYCN amplified cells.