MYCN expression induces replication stress and sensitivity to PARP inhibition in neuroblastoma.

David King,Gilberto S Almeida,Louis Chesler,Daniel Harrison,Saoirse Burke,Daniel Yeomanson,Yann Jamin,Simon P Robinson,Xiao Dun Li,Evon Poon,Albert Hallsworth,Christopher J Lord,Colin Kwok,Helen E Bryant,Sally George,Polly Gravells

doi:10.18632/oncotarget.27329

Abstract

This study investigates the influence expression of the MYCN oncogene has on the DNA damage response, replication fork progression and sensitivity to PARP inhibition in neuroblastoma. In a panel of neuroblastoma cell lines, MYCN amplification or MYCN expression resulted in increased cell death in response to a range of PARP inhibitors (niraparib, veliparib, talazoparib and olaparib) compared to the response seen in non-expressing/amplified cells. MYCN expression slowed replication fork speed and increased replication fork stalling, an effect that was amplified by PARP inhibition or PARP1 depletion. Increased DNA damage seen was specifically induced in S-phase cells. Importantly, PARP inhibition caused a significant increase in the survival of mice bearing MYCN expressing tumours in a transgenic murine model of MYCN expressing neuroblastoma. Olaparib also sensitized MYCN expressing cells to camptothecin- and temozolomide-induced cell death to a greater degree than non-expressing cells. In summary, MYCN expression leads to increased replication stress in neuroblastoma cells. This effect is exaggerated by inhibition of PARP, resulting in S-phase specific DNA damage and ultimately increased tumour cell death. PARP inhibition alone or in combination with classical chemotherapeutics is therefore a potential therapeutic strategy for neuroblastoma and may be more effective in MYCN expressing tumours.

Highlights

Neuroblastoma (NB), a tumour derived from primitive neural crest cells in the sympathetic nervous system, is the most common extracranial solid childhood tumour [1, 2]
This study investigates the influence expression of the MYCN oncogene has on the DNA damage response, replication fork progression and sensitivity to Poly(ADP-ribose) polymerase (PARP) inhibition in neuroblastoma
To examine further the ability of MYCN expression to influence sensitivity to PARP inhibition and to test the influence of trapping, the cytotoxicity of three PARP inhibitors, talazoparib, www.oncotarget.com olaparib and veliparib, was compared by MTT assay in the NB cell lines, IMR-32 (MYCN-amplified) and SHEP1

Summary

Introduction

Neuroblastoma (NB), a tumour derived from primitive neural crest cells in the sympathetic nervous system, is the most common extracranial solid childhood tumour [1, 2]. Patients with NB are stratified into risk groups depending on a number of features, including age at diagnosis, stage, MYCN amplification status and DNA ploidy [3]. At the time of diagnosis, the majority of patients have high-risk disease, defined as the presence of stage IV disease or amplification of the MYCN oncogene. MYCN amplification is present in 25% of NB patients and strongly predicts poor prognosis independently of other factors [4, 5]. The majority of patients with amplification display high MYCN expression. We are at the stage where conventional therapy is at the limits of tolerability and novel therapies targeting the molecular drivers of NB are urgently needed. As a driver of neuroblastoma, associated with poor outcome, MYCN is an important potential therapeutic target for high-risk NB. Increased understanding of MYCN biology is needed in order that alternative ways to exploit MYCN expression can be explored

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Results

Conclusion