Oral Presentation Advances in Neuroblastoma Research Congress 2016

Sensing mutant ALK: capicua and ETV5 as executors of aberrant ALK-driven MAPK signaling in neuroblastoma (#36)

Irina Lambertz 1 2 , Liselot Mus 1 2 , Candy Kumps 3 , Shana Claeys 1 2 , Wouter Van Loocke 1 2 , Christophe Van Neste 1 2 , Jan Koster 4 , Rogier Versteeg 4 , Nadine Van Roy 1 2 , Bram De Wilde 1 2 5 , Genevieve Laureys 2 5 , Johannes Schulte 6 7 8 9 , Olivier De Wever 2 10 , Katleen De Preter 1 2 , Frank Speleman 1 2
  1. Center for Medical Genetics, Ghent University, Ghent, Belgium
  2. Cancer Research Institute Ghent (CRIG), De Pintelaan, Ghent, Belgium
  3. Department of Uro-gynaecology, Ghent University Hospital, Ghent, Belgium
  4. Department of Oncogenomics, Academic Medical Center, Amsterdam, The Netherlands
  5. Department of Pediatric Hematology and Oncology, Ghent University Hospital, Ghent, Belgium
  6. Department of Pediatric Oncology and Haematology, University Children’s Hospital Essen, Essen, Germany
  7. Department of Pediatric Oncology and Hematology, Charité University Medical Center Berlin, Berlin, Germany
  8. German Cancer Consortium (DKTK), Berlin, Germany
  9. German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
  10. Laboratory of Experimental Cancer Research, Ghent University, Ghent, Belgium

Activating ALK mutations occur in 10% of neuroblastomas (NB) and represent an important novel druggable target for more effective treatment of high-risk patients. Importantly, ALK mutations emerged as an important event in relapsed cases. In order to design effective novel targeted therapeutic approaches, gaining detailed insights into downstream ALK signaling is crucial. We and others identified PI3K/mTOR and RAS/MAPK as major downstream signaling axes. Also, we connected FOXO3a controlled RET expression to the PI3K/mTOR axis. Here, using multiple ALK activating and inhibiting cell models, we firmly establish ETV5 as a major RAS/MAPK downstream target upregulated through mutant ALK. ETV5 is known to act as a regulator of epithelial-mesenchymal transition (EMT) and controls stem cell properties and neuronal cell fate decisions. Knockdown of ETV5 reduced the clonogenic potential and growth of NB cells in vitro and in vivo. RNAseq transcriptome profiling following ETV5 knockdown provided an ETV5 signature score which identifies patients with poor overall survival and showed enrichment in gene sets controlling EMT, in keeping with observed reduced invasive properties in ETV5 depleted NB cell lines. Of further interest, transcription factor target enrichment analysis shows that downregulated genes following ALK inhibition are significantly enriched in targets of Capicua (CIC). Essentially, CIC is a RAS/MAPK responsive gene, negatively regulating ETV5 in melanoma, and acting as general sensor for RTK signalingby repressing gene expression. CIC is located on a 19q13.2 segment of recurrent loss in NB and we found two putative inactivating insertions in the CIC gene in NB cell lines. In conclusion, our data highlight CIC and ETV5 as intrinsic components of ALK - RAS/MAPK signaling in NB with immediate potential relevance given that deregulation of this axis can provide NB cells with EMT plasticity leading to stemness features, improved migratory capacity and therapy resistance.