Abstract 4886: The BRIP1 DNA helicase is a 17q dosage sensitive cooperative driver in neuroblastoma
Authors: Vanhauwaert Suzanne , Durinck Kaat , Janssens Els , Dewyn Givani , Wilde Bram De , Laureys Genevieve , Carter Daniel , Belamy Chueng , Preter Katleen De , Vanneste Christophe , Speleman Frank 
Published: July 2017

Abstract
Neuroblastoma (NB) is an aggressive pediatric tumor arising from sympathetic neuronal progenitors. NBs have a low mutation burden while copy number alterations are highly recurrent: MYCN amplification is present in half of high risk tumors often accompanied by 1p deletions while MYCN non-amplified aggressive NB frequently exhibit 11q deletions. Remarkably, both high risk groups show almost invariably chromosome 17q gain and we also reported that the mouse syntenic chromosome 11 region was gained during MYCN driven tumor formation. We propose that one or more dosage sensitive genes on 17q act as cooperative drivers during NB development. Using an integrated bioinformatics analysis, we identified several candidate drivers implicated in DNA repair including BRIP1, also known as FANCJ and located on 17q23.2. BRIP1 acts as a DNA helicase in unwinding of stable G-quadruplex (G4) structures in single stranded DNA during replication ensuring timely progression through S-phase. We show that BRIP1 knock down causes increased replicative stress in MYCN overexpressing NB cells as evidenced as shown by increased RPA32 levels and reduced replication fork velocity. Overexpression of BRIP1 in dβh-MYCN-eGFP transgenic zebrafish caused accelerated tumor formation supporting its role as cooperative driver gene. Gene expression profiling after BRIP1 knock down confirmed enrichment for gene sets implicated in DNA replication and repair and are indicative for perturbation of G4 enriched genes. We also identified further additional 17q dosage sensitive genes implicated in replication fork dynamics including BRCA1, BRCA2, EME1 and TOP2A. We propose that 17q gain acts as an amplifier for expression of multiple genes implicated in control of replicative stress and replication fork dynamics. Finally, we explored whether this replicative stress resistance phenotype could represent a novel therapeutic vulnerability for NB cells or other MYC(N) driven tumor entities. To this end, we tested several compounds for synergistic interaction with G4 stabilizing ligands such as TMPYP4, pyridostatin and BRACO-19 with promising results. In conclusion, we identified BRIP1 as 17q cooperative driver in NB through relief from G4 induced replication fork stalling in rapidly dividing tumor cells. Further, NB cells exhibit replicative stress resistance through upregulation of multiple critical regulators of replication fork dynamics, offering a new venue for therapeutic interventions.
Citation Format: Suzanne Vanhauwaert, Kaat Durinck, Els Janssens, Givani Dewyn, Bram De Wilde, Genevieve Laureys, Daniel Carter, Chueng Belamy, Katleen De Preter, Christophe Vanneste, Frank Speleman. The BRIP1 DNA helicase is a 17q dosage sensitive cooperative driver in neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4886. doi:10.1158/1538-7445.AM2017-4886