Regulation of Nuclear Hormone Receptors by MYCN-Driven miRNAs Impacts Neural Differentiation and Survival in Neuroblastoma Patients

Abstract

MYCN amplification and MYC signaling are associated with high-risk neuroblastoma with poor prognosis. Treating these tumors remains challenging, although therapeutic approaches stimulating differentiation have generated considerable interest. We have previously shown that the MYCN-regulated miR-17∼92 cluster inhibits neuroblastoma differentiation by repressing estrogen receptor alpha. Here, we demonstrate that this microRNA (miRNA) cluster selectively targets several members of the nuclear hormone receptor (NHR) superfamily, and we present a unique NHR signature associated with the survival of neuroblastoma patients. We found that suppressing glucocorticoid receptor (GR) expression in MYCN-driven patient and mouse tumors was associated with an undifferentiated phenotype and decreased survival. Importantly, MYCN inhibition and subsequent reactivation of GR signaling promotes neural differentiation and reduces tumor burden. Our findings reveal a key role for the miR-17∼92-regulated NHRs in neuroblastoma biology, thereby providing a potential differentiation approach for treating neuroblastoma patients.

Neuroblastoma patient-derived xenograft cells cultured in stem-cell promoting medium retain tumorigenic and metastatic capacities but differentiate in serum

“…Glucocorticoid receptor signaling has been reported to promote differentiation of neuroblastoma cells 26 . Since serum contains glucocorticoids we tested if 10% lipid-free, charcoal-stripped serum would induce differentiation.…”

“…Considering the significance of MYCN in neuroblastoma, our observation that MYCN was the top downregulated transcript in serum-grown PDX cells is intriguing. As well as being essential for normal neurogenesis 33 , MYCN has been shown to prevent neuronal differentiation 26 , 34 , 35 , although overexpression of MYCN in non- MYCN -amplified SK-N-SH cells did not impede differentiation induced by several different protocols 36 . Treatment with the MYC-MAX inhibitor 10058-F4 promoted expression of a few, but not all of the differentiation markers tested, showing that MYCN inhibition alone cannot substantially push the PDX cells towards a more differentiated stage.…”

“…It was recently shown that MYCN -regulated miRNAs inhibit the expression of several nuclear hormone receptors, including the glucocorticoid hormone receptor, and simultaneous inhibition of MYCN and activation of glucocorticoid signaling resulted in differentiation of neuroblastoma cells 26 . Our data show that charcoal-stripped serum devoid of steroids promoted MYCN downregulation and increased the expression of differentiation markers in the PDX cells, however it did not promote attachment or morphological differentiation.…”

The MYCN Protein in Health and Disease

“…The conserved transcriptional activation domain (TAD) is located in the N-terminus while the bHLHZip and nuclear localization sequences (NLS) are found in the C-terminus of the respective proteins (Figure 1). MYC is normally unstructured until dimerization with the MYC-associated protein X (MAX) to assist in DNA interaction [4,5]. The MYC family and its extended protein network is important in regulating several processes such as cell growth, differentiation and apoptosis [6].…”

<i>hsa-miR-543</i> Acts as a Tumor Suppressor by Targeting <i>NMYC</i>

“…Deregulated MYCN signaling supports the development of several different tumors, mainly with a childhood onset, including neuroblastoma, medulloblastoma, rhabdomyosarcoma and Wilms' tumor, but it is also associated with some cancers occurring during adulthood such as prostate and lung cancer. In neuroblastoma, MYCNamplification is the most consistent genetic aberration associated with poor prognosis and treatment failure [28][29]. Targeting MYCN has been proposed as a therapeutic strategy for the treatment of these tumors and great efforts have allowed the development of direct and indirect MYCN inhibitors with potential clinical use.…”