MYCN in neuroblastoma: The kings' new clothes and drugs

Deregulated levels of the MYCN oncogene contribute to the tumorigenesis of several human tumors including neuroblastoma. MYCN amplification classifies neuroendocrine tumors as high-risk and as a consequence is an unfavorable prognostic factor. MYCN has long been primarily described as a transcription factor, which binds to active promoters after heterodimerizing with MAX and directly regulates gene expression programs. New findings show that MYC proteins have novel oncogenic functions that are tumor-promoting and go beyond the regulation of gene expression. This review describes how MYCN continuously drives tumor progression by forming various protein complexes, for example to resolve torsional stress, coordinate transcription and replication, repair DNA damage and regulate R-loops. Interfering with the described processes as well as interfering with MYCN chromatin binding emerge as novel treatment strategies to indirectly target the oncoprotein. Furthermore, we describe the role of MYCN in metabolism and we review how these newly described functions of MYCN could be used as vulnerabilities for MYCN-driven tumors. Recent studies show that MYC proteins are capable of multimerizing at sites of genomic instability to protect cancer cells from stress. Additionally, MYCN can bind aberrant RNA transcripts, another feature to enhance the stress resilience of cancer cells, once again highlighting the oncogenic potential of MYC. Taken together, we show that the diverse functions of MYCN depend on its temporal and spatial dynamic interactome, making those interaction partners and functions crucial factors in the treatment of MYCN-related cancer.