The MicroRNA Landscape of MYCN-Amplified Neuroblastoma

Abstract

MYCN gene amplification and upregulated expression are major hallmarks in the progression of high-risk neuroblastoma. MYCN expression and function in modulating gene synthesis in neuroblastoma is controlled at virtually every level, including poorly understood regulation at the post-transcriptional level. MYCN modulates the expression of various microRNAs including the miR-17-92 cluster. MYCN mRNA expression itself is subjected to the control by miRNAs, most prominently the miR-17-92 cluster that balances MYCN expression by feed-back regulation. This homeostasis seems disturbed in neuroblastoma where MYCN upregulation coincides with severely increased expression of the miR-17-92 cluster. In the presented study, we applied high-throughput next generation sequencing to unravel the miRNome in a cohort of 97 neuroblastomas, representing all clinical stages. Aiming to reveal the MYCN-dependent miRNome, we evaluate miRNA expression in MYCN-amplified as well as none amplified tumor samples. In correlation with survival data analysis of differentially expressed miRNAs, we present various putative oncogenic as well as tumor suppressive miRNAs in neuroblastoma. Using microRNA trapping by RNA affinity purification, we provide a comprehensive view of MYCN-regulatory miRNAs in neuroblastoma-derived cells, confirming a pivotal role of the miR-17-92 cluster and moderate association by the let-7 miRNA family. Attempting to decipher how MYCN expression escapes elevated expression of inhibitory miRNAs, we present evidence that RNA-binding proteins like the IGF2 mRNA binding protein 1 reduce miRNA-directed downregulation of MYCN in neuroblastoma. Our findings emphasize the potency of post-transcriptional regulation of MYCN in neuroblastoma and unravel new avenues to pursue inhibition of this potent oncogene.

MYCN Impact on High-Risk Neuroblastoma: From Diagnosis and Prognosis to Targeted Treatment

“…MiRNAs targeting MYCN were found to be particularly important in regulating its expression in neuroblastoma in different ways [ 8 , 226 ]. Some miRNAs targeting MYCN, such as the let-7 family, work as inhibitors [ 227 ] and are down-regulated in neuroblastoma, inducing N-Myc protein expression [ 228 , 229 , 230 ]. These miRNA types are considered the most common, but other miRNAs were found to work with the opposite mechanism.…”

“…For instance, miRNAs such as the family of miR-17-92 are substantially employed as MYCN up-regulators. Interestingly N-Myc is able to stimulate the expression of miR-17-92 cluster, suggesting the presence of a positive feedback mechanism of regulation between MYCN and the miR-17-92 cluster itself [ 230 , 231 , 232 ].…”

MYCN in Neuroblastoma: “Old Wine into New Wineskins”

“…The result from the interaction between miRNAs and mRNAs is the silencing of the second, through three main processes; The first concerns mRNA cleavage, the second concerns the destabilization of the mRNA through shortening of its poly(A) tail, and finally the third concerns the inhibition of translation in the ribosomes [ 123 ]. Similarly, the MYCN gene is known to be regulated by miRNAs [ 124 ]. A search for possible miRNA targets of MYCN revealed a total of 234 miRNAs, using the miRDB database [ 125 , 126 , 127 , 128 ], which we present in the Supplementary Materials Table S1 .…”

A New Player in Neuroblastoma: YAP and Its Role in the Neuroblastoma Microenvironment

“…However, in vivo treatment with single-agent binimetinib in various neuroblastoma cell line-derived xenograft models demonstrated inhibition of tumor growth and extended survival in NRAS or NF1 mutated xenografts while ALK mutated tumors did not respond, likely due to persistent or alternative tyrosine kinase pathway activation [ 8 , 93 ]. Moreover, there may be a role for microRNAs such as the let-7 microRNA family for contributing to ALK inhibitor therapy resistance by regulating RAS expression [ 94 , 95 ]. Therefore, these findings suggest the need for combined targeting of pathways.…”