Poster Presentation Advances in Neuroblastoma Research Congress 2016

MYCN promotes neuroblastoma malignancy by establishing a regulatory circuit with transcription factor AP4 (#375)

Cheng Xue 1 , Denise Yu 1 , Samuele Gherardi 2 , Jessica Koach 1 , Giorgio Milazzo 2 , Laura Gamble 1 , Bing Liu 1 , Amanda Russell 1 , Tao Liu 1 , Belamy Cheung 1 , Glenn Marshall 1 , Giovanni Perini 2 , Michelle Haber 1 , Murray Norris 1
  1. Children’s Cancer Institute, Lowy Cancer Research Centre, University of New South Wales, Sydney, NSW, Australia
  2. Department of Pharmacy and Biotechnology, CIRI Health Sciences and Technologies University of Bologna, Bologna, Italy

Amplification of the MYCN oncogene, a member of the MYC family of transcriptional regulators, is one of the most powerful prognostic markers identified for poor outcome in neuroblastoma, the most common extracranial solid cancer in childhood. While MYCN has been established as a key driver of malignancy in neuroblastoma, the underlying molecular mechanisms are poorly understood. Transcription factor activating enhancer binding protein-4 (TFAP4) has been reported to be a direct transcriptional target of MYC. We show for the first time that high expression of TFAP4 in primary neuroblastoma patients is associated with poor clinical outcome. siRNA-mediated suppression of TFAP4 in MYCN-expressing neuroblastoma cells impaired migration and colony formation, and led to cell cycle arrest in G1/S phase. Chromatin immunoprecipitation assay demonstrated that TFAP4 expression is positively regulated by MYCN. Furthermore, when MYCN was overexpressed in neuroblastoma cells, TFAP4 was required for the observed increase in cell migration. Microarray analysis identified genes regulated by both MYCN and TFAP4 in neuroblastoma cells, including Phosphoribosyl-pyrophosphate synthetase-2 (PRPS2) and Syndecan-1 (SDC1), which are involved in cancer cell proliferation and metastasis. Overall this study unveils a regulatory circuit in which MYCN by elevating TFAP4 expression, cooperates with it to control a specific set of genes involved in tumor progression. These findings highlight the existence of a MYCN-TFAP4 axis in MYCN-driven neuroblastoma as well as identifying potential therapeutic targets for aggressive forms of this disease.