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), which plays important roles in cancer progression, has been reported to be a direct transcriptional target of MYC. In this study, we have shown that high expression of TFAP4 in primary neuroblastoma patients is associated with poor clinical outcome and furthermore that siRNA-mediated suppression of TFAP4 in MYCN-expressing neuroblastoma cells impaired migration and colony formation, and led to an increased proportion of cells in G1/S phase of the cell cycle. Chromatin immunoprecipitation and luciferase reporter assays demonstrated that TFAP4 expression is positively regulated by MYCN through direct promoter binding. In addition, 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 complex 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 relevant therapeutic targets for aggressive forms of this disease.
Citation Format: Chengyuan Xue, Denise M. Yu, Samuele Gherardi, Jessica Koach, Giorgio Milazzo, Laura Gamble, Bing Liu, Amanda Russell, Tao Liu, Belamy B. Cheung, Glenn M. Marshall, Giovanni Perini, Michelle Haber, Murray D. Norris. MYCN and TFAP4 promote neuroblastoma malignancy by cooperating in the regulation a subset of target genes involved in cancer cell growth and metastasis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2450.