Cellular Retinoic Acid–Binding Protein II Is a Direct Transcriptional Target of MycN in Neuroblastoma

Abstract

Neuroblastoma is a heterogeneous disease in which 22% of tumors show MycN oncogene amplification and are associated with poor clinical outcome. MycN is a transcription factor that regulates the expression of a number of proteins that affect the clinical behavior of neuroblastoma. We report here that cellular retinoic acid-binding protein II (CRABP-II) is a novel MycN target, expressed at significantly higher levels in primary neuroblastoma tumors with mycN oncogene amplification as compared with non-MycN-amplified tumors. Moreover, regulated induction and repression of MycN in a neuroblastoma-derived cell line resulted in temporal and proportionate expression of CRABP-II. CRABP-II is expressed in several cancers, but its role in tumorigenesis has not been elucidated. We show that MycN binds to the promoter of CRABP-II and induces CRABP-II transcription directly. In addition, CRABP-II-transfected neuroblastoma cell lines show an increase in MycN protein levels resulting in increased cell motility. Gene expression profiling of CRABP-II-expressing cell lines uncovered increased expression of the HuB (Hel N1) gene. Hu proteins have been implicated in regulating the stability of MycN mRNA and other mRNAs by binding to their 3 ¶ untranslated regions. We did not, however, observe any change in MycN mRNA stability or protein half-life in response to CRABP-II expression. In contrast, de novo MycN protein synthesis was increased in CRABP-II-expressing neuroblastoma cells, thereby suggesting an autoregulatory loop that might exacerbate the effects of MycN gene amplification and affect the clinical outcome. Our findings also suggest that CRABP-II may be a potential therapeutic target for neuroblastoma.

MycN is a transcriptional regulator of livin in neuroblastoma

“…We found that MycN induction rapidly upregulated livin expression. This system has been widely used to investigate MycN regulation of a number of target genes in neuroblas- toma (25,27,28). Our results with the MYCN-inducible system complement and reinforce our data from the MYCNknockdown experiments.…”

“…We detected a consensus MycN binding domain within the 5' proximal sequence of the putative livin promoter. Similar direct binding of MycN to E-boxes within the target promoters of MDM2, MRP1 and CRABII in neuroblastoma cells have been reported as evidence that MycN positively regulates expression of these genes (25,27,28). We are currently characterizing the role of this MycN binding site in the livin promoter by mutation/deletion experiments.…”

“…MycN is involved in regulating a diverse set of genes involved in cell-cycle progression and cell survival (25)(26)(27)(28). Prior to the present study, a role for MycN in regulating members of the IAP family of anti-apoptotic proteins has not been reported.…”

Unveiling MYCN regulatory networks in neuroblastoma via integrative analysis of heterogeneous genomics data

“…In addition, several known MYCN-regulated genes (NME2 [20], CRABP2 [21], LIF [22], MDM2 [23], MIR17HG [24], PRMT1 [25], MCM7 [26], MCM8 [26], ODC1 [27], BIRC5 [28], LUC7L [29], TWIST1 [30], RAB5C [31], AURKA [31], H1F0 [31], and MYBL2 [32]) were successfully detected in the ChIP-seq experiments (Supplementary Figure S2). To study the distribution of MYCN binding around promoter sequences, we aligned the peaks with the annotated transcriptional start sites (TSSs), which were provided by RefSeq.…”

CRABP proteins – relatives or homonyms?

“…Соответ-ственно, возникает петля положительной обратной связи, приводящая к усилению малигнизации клеток. Авторы даже предлагают использовать CRABP2 в ка-честве мишени для таргетной терапии при данном заболевании [99].…”