Oral Presentation Advances in Neuroblastoma Research Congress 2016

The HBP1 tumor suppressor is a negative epigenetic regulator of MYCN driven neuroblastoma through interaction with the PRC2 complex. (#43)

Shana Claeys 1 2 , Irina Lambertz 1 2 , Els Janssens 1 2 , Suzanne Vanhauwaert 1 2 , Bieke Decaesteker 1 2 , Candy Kumps 3 , Sara De Brouwer 1 , Annelies Fieuw 1 , Tom Vanmaerken 1 2 , Bram De Wilde 1 2 4 , Genevieve Laureys 2 4 , Kristina Althoff 5 , Johannes Schulte 5 6 7 8 , Laurel Bate-Eya 9 , Jan J. Molenaar 9 , Jean-Baptiste Demoulin 10 , A. Thomas Look 11 , Katleen De Preter 1 2 , Frank Speleman 1 2
  1. Center for Medical Genetics, Ghent University, Ghent, Belgium
  2. Cancer Research Institute Ghent (CRIG), Ghent University, Ghent, Belgium
  3. Department of Uro-gynaecology, Ghent University Hospital, Ghent, Belgium
  4. Department of Pediatric Oncology and Haematology, Ghent University Hospital, Ghent, Belgium
  5. Department of Pediatric Oncology and Haematology, University Children’s Hospital Essen, Essen, Germany
  6. Department of Pediatric Oncology and Haematology, Charite University Hospital Berlin, Berlin, Germany
  7. German Translational Cancer Research Consortium (DKTK), Berlin, Germany
  8. German Translational Cancer Research Consortium (DKFZ), Heidelberg, Germany
  9. Department of Oncogenomics, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
  10. De Duve Institute, University of Louvain – UCL, Brussels, Belgium
  11. Department of Pediatric Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts, USA

The MYCN oncogene signaling pathway is a key driver in initiation and progression of neuroblastoma (NB) and represents a major target for novel drug strategies. We previously identified the MYC repressor HBP1 as a robust mutant ALK regulated gene. Pharmacological pathway analysis of mutant ALK NB cells allowed to identify HBP1 as a transcription factor downstream of the PI3K-AKT-FOXO3 signaling axis. 

Here, we show that HBP1 upregulation represses MYCN signaling and activity and negatively impacts on cell growth. Acceleration of dbh-MYCN driven neuroblastoma formation was shown in HBP1 deficient zebrafish background, supporting the tumor suppressor role for HBP1. Next, we showed that MYCN represses HBP1 levels through the miR-17~92 cluster. Unraveling of the ALK-HBP1-PI3K-AKT-FOXO3 and the MYCN-miR-17~92-HBP1 axis suggested new opportunities for more precise combination treatments of neuroblastoma tumors with activated ALK and/or MYCN. Indeed, combining EGCG, a HBP1 upregulating tool compound, with the BET inhibitor JQ1 showed both in vitro and in vivo synergistic effects, while the PI3K/mTOR dual inhibitor BEZ-235 together with JQ1 also showed very strong synergistic effects. Further dissection of the HBP1 regulome was done using Gene Set Enrichment Analysis (GSEA) and iRegulon analysis (http://iregulon.aertslab.org), identifying SUZ12 as a central node in HBP1 regulated signaling, mainly through controlling the repression of MYCN regulated genes. As SUZ12 and EZH2 form the repressive PRC2 epigenetic regulatory protein complex, comparison of HBP1 and EZH2 regulated genes was performed, which revealed two interesting druggable targets: a novel candidate differentiation gene ARHGEF16 and the pro-apoptotic and HDAC inhibitor sensitizing CTSL2 gene. Based on these findings, further drugging efforts include combined EZH2/PI3K-AKT as well as EZH2/HDAC inhibition. 

We conclude that HBP1 is a crucial component in MYCN controlled repression of gene activity through PRC2 interaction and demonstrate novel opportunities for precision drugging of MYCN overexpressing NB cells.