Katleen De Preter, Frank Speleman: equally contributed
Neuroblastoma (NB) is characterised by a low mutational burden while exhibiting highly recurrent large DNA copy number alterations including 17q gain in aggressive NBs. Together with the finding of gain of a large mouse chromosome 11 segment syntenic to human chromosome 17q in MYCN driven NB mouse models this strongly supports a crucial role for 17q gain in human NB formation and suggests the presence of oncogenic drivers at this genomic location. To prioritize 17q candidate genes we combined analysis of dynamic upregulation during MYCN driven tumour formation in mice with super-enhancer analysis based on H3K27 acetylation marks near candidate genes. We observed a significant higher number of 17q super-enhancers in MYCN amplified NB cell lines versus MYCN single copy cell lines suggesting that MYCN acts as amplifier to boost activation of super-enhancers on 17q leading to overexpression of target genes. Integration with expression profiling data allowed to prioritize the T-box2 transcription factor (TBX2) as strong candidate MYCN cooperative driver gene. In a panel of tumour cell lines TBX2 was most highly expressed in NB. Importantly, in primary NBs, high TBX2 expression was correlated with unfavorable prognosis. Moreover, TBX2 is upregulated in tumours of the LSL-MYCN mouse as compared to normal adrenal tissue and ChIP-sequencing data indicated binding of MYCN to the TBX2 super-enhancer and promotor region. TBX2 plays a central role during embryonal development and was implicated in bypassing senescence and inducing EMT in cancer. Knockdown was shown to impair growth in NB cells. Further functional assays are ongoing, zebrafish modeling has been initiated and TBX2 ChIP-sequencing and RNA-sequencing following TBX2 knockdown will allow to unravel the TBX2 regulome. In conclusion, we identified TBX2 as highly expressed 17q gene marked by super-enhancer activity in MYCN driven NB formation and propose TBX2 and TBX2 controlled signaling as novel drug target.