MYCN acts as a direct co-regulator of p53 in MYCN amplified neuroblastoma

// Saurabh Agarwal 1, * , Giorgio Milazzo 2, * , Kimal Rajapakshe 3, * , Ronald Bernardi 1 , Zaowen Chen 1 , Eveline Barberi 1 , Jan Koster 4 , Giovanni Perini 2, ** , Cristian Coarfa 3, ** and Jason M. Shohet 1, ** 1 Division of Hematology-Oncology, Department of Pediatrics, Baylor College of Medicine, Houston, Texas, USA 2 Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy 3 Dan L Duncan Cancer Center, Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA 4 Department of Oncogenomics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands * These authors are considered as co-first authors ** These authors are considered as co-last authors Correspondence to: Jason M. Shohet, email: jmshohet@txch.org Cristian Coarfa, email: coarfa@bcm.edu Giovanni Perini, email: Giovanni.perini@unibo.it Keywords: neuroblastoma; MYCN; p53; p53 C-terminal domain; DNA damage resposone Received: January 19, 2018      Accepted: March 06, 2018      Published: April 17, 2018 ABSTRACT The MYC oncogenes and p53 have opposing yet interrelated roles in normal development and tumorigenesis. How MYCN expression alters the biology and clinical responsiveness of pediatric neuroblastoma remains poorly defined. Neuroblastoma is p53 wild type at diagnosis and repression of p53 signaling is required for tumorigenesis. Here, we tested the hypothesis that MYCN amplification alters p53 transcriptional activity in neuroblastoma. Interestingly, we found that MYCN directly binds to the tetrameric form of p53 at its C-terminal domain, and this interaction is independent of MYCN/MAX heterodimer formation. Chromatin analysis of MYCN and p53 targets reveals dramatic changes in binding, as well as co-localization of the MYCN-p53 complex at p53-REs and E-boxes of genes critical to DNA damage responses and cell cycle progression. RNA sequencing studies show that MYCN-p53 co-localization significantly modulated the expression of p53 target genes. Furthermore, MYCN-p53 interaction leads to regulation of alternative p53 targets not regulated in the presence of low MYCN levels. These novel targets include a number of genes involved in lipid metabolism, DNA repair, and apoptosis. Taken together, our findings demonstrate a novel oncogenic role of MYCN as a transcriptional co-regulator of p53 in high-risk MYCN amplified neuroblastoma. Targeting this novel oncogenic function of MYCN may enhance p53-mediated responses and sensitize MYCN amplified tumors to chemotherapy.