Poster Presentation 37th Lorne Cancer Conference 2025

Targeting the interplay between replication stress (RS) induced DNA damage response (DDR) and epigenetics in children with high-risk neuroblastoma and sarcoma (#152)

Hannah E. Hartley 1 2 , Gabor Tax 1 , Jie Mao 1 , Alvin Kamili 1 2 , Jamie Fletcher 1 2 , Orazio Vittorio 1 3 , Fatima Valdes Mora 1 2 , Emmy M. Dolman 1 2 4
  1. Children's Cancer Institute, Lowy Cancer Research Centre, UNSW Sydney, Kensington, Sydney , New South Wales , Australia
  2. School of Clinical Medicine, UNSW Medicine & Health, UNSW Sydney, Kensington, Sydney , New South Wales , Australia
  3. School of Biomedical Sciences, Faculty of Medicine and Health, University of New South Wales, Sydney , New South Wales, Australia
  4. Princess Maxima Center for Pediatric Oncology, Utrecht , Netherlands

Introduction. Disrupting pediatric cancer cell dependency on the replication stress (RS) response by ATR inhibition is a promising strategy towards improving survival outcomes of children with neuroblastoma and sarcoma by inducing lethal DNA damage1. However, combination therapies are needed to overcome monotherapy resistance. Epigenetic mechanisms are essential for DNA repair; therefore, combined ATRi and epigenetic targeting will exacerbate RS and DNA damage in RS-response dependent neuroblastoma and sarcoma to induce cell killing.

Aim. Exploit the interplay between the DNA damage response (DDR) and epigenetics by combining ATRi and epigenetic targeting as a personalized approach for children with high-risk neuroblastoma and sarcoma.

Methods. Gene Set Enrichment Analysis of transcriptomic (RNA-seq) data from patients enrolled onto the Australian ZERO Childhood Cancer program was undertaken to uncover the DDR and epigenetic landscapes of neuroblastoma and sarcomas. ATRi or epigenetic targeted drugs were tested alone to establish ex vivo effects on cell viability using ZERO neuroblastoma and sarcoma samples. ATR inhibitor (AZD6738/Cerelasertib) combinations with epigenetic drugs causing chromatin closing: bromodomain/histone acetyltransferase (HAT) inhibitors (BI-894999, CBP30, BMS-986158), histone demethylase (KDM) inhibitors (GSK-J4), or chromatin opening: DNA methyltransferase inhibitors (OTS186935, Decitabine), histone deacetylase (HDAC) inhibitors (Panobinostat, Entinostat, Vorinostat) were tested in neuroblastoma and sarcoma cell lines.

Results. Our analysis revealed differential enrichment of neuroblastoma and sarcomas in genes associated with DDR and epigenetic pathways, consistently including histone acetylation and double-strand break repair pathways. Single-agent ATRi demonstrated highest efficacy in MYCN-amplified neuroblastoma and rhabdomyosarcoma, whilst epigenetic targeting showed varying effects across all subtypes. Combined ATR and bromodomain/HAT inhibition achieved strongest synergism in non-MYCN and MYCN-amplified neuroblastoma cell lines, with high overall efficacy. Combined ATR and HDAC inhibition was synergistic in MYCN-amplified neuroblastoma cell lines. Further strong synergism was achieved with combined ATR and bromodomain/HAT inhibition in fusion-negative sarcoma cell lines.

Conclusion. Clinical stage ATR inhibitor and epigenetic targeted drug combinations, particularly bromodomain/HAT inhibitors, demonstrate strong synergistic effects in neuroblastoma and sarcoma cell lines in the presence or absence of MYCN-induced RS. These combinations offer superior efficacy than either drug alone. Functional studies will elucidate mechanisms responsible for observed synergy, and effective combinations will be validated in vivo.

  1. Ngoi, N.Y.L., Pilié, P.G., McGrail, D.J.. Zimmerman M., Schlacher K., & Yap T.A. (2024) Nat Rev Clin Oncol 21, 278–293.