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SNRPD3 preserves balanced MYCN-driven alternate splicing and represents a therapeutic vulnerability in neuroblastoma

ABSTRACT: Many of the pro-tumorigenic functions of the oncogene MYCN are attributed to its regulation of global gene expression programs. Alternative splicing is another important regulator of gene expression and has been implicated in neuroblastoma development, however, the molecular mechanisms behind this remain unknown. We found that MYCN up-regulated the core spliceosomal protein, SNRPD3, in models of neuroblastoma initiation and progression. MYCN directly bound SNRPD3, and the protein arginine methyltransferase, PRMT5. RNA-sequencing revealed a global increase in the number of genes being differentially spliced when MYCN was overexpressed, while depletion of SNPRD3 in the presence of overexpressed MYCN was sufficient to induce additional increases in differential splicing, particularly genes involved in the cell cycle. SNRPD3 knockdown in the presence of MYCN was accompanied with marked loss of cell viability, suggesting that SNRPD3 maintains splicing balance for MYCN, and prevents detrimental differential splicing of cell cycle genes in neuroblastoma. Further analysis revealed BIRC5 and CDK10 to be among the topmost differentially spliced cell cycle genes, both of which play a role in the G2/M phase of the cell cycle. Flow cytometry analysis revealed that depletion of SNRPD3 resulted in G2/M cell cycle arrest. Furthermore, SNRPD3 was an oncogenic co-factor for MYCN in vitro and in vivo. As such, SNRPD3 represents a therapeutic vulnerability for neuroblastoma cells in the presence of high MYCN expression. Indeed, the PRMT5 inhibitor, JNJ-64619178, that prevents SNRPD3 methylation was cytotoxic in neuroblastoma cell lines with high SNRPD3 and MYCN expression. Overall, our findings demonstrate a selective relationship exhibited between MYCN and SNRPD3 and suggest that SNRPD3 plays a vital role in MYCN-driven tumorigenesis and could serve as a novel therapeutic target.

ORGANISM(S): Homo sapiens

PROVIDER: GSE213762 | GEO | 2024/02/13

REPOSITORIES: GEO

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Project description:Neuroblastoma (NB) is an aggressive tumor that affects both infants and children. The disease outcome is greatly influenced by age of patient, stage, chromosome copy number aberrations (CNAs) and gene expression abnormalities. We analyzed, by microarray technology, genome and transcriptome of 3 groups of tumors of patients with metastatic disease: G1, stage 4S and MYCN single copy; G2, stage 4 younger than 18 months of age, MYCN single copy with no disease progression and G3, stage 4, older than 19 months, with unfavorable outcome. We found an accumulation of structural copy number aberrations (CNAs) in G3 whereas G1 tumors had mostly numerical (N) CNAs and G2 showed an intermediate behavior. Pair wise comparisons demonstrated that the average of N CNAs significantly decreased from G1 to G2 to G3 (9.6 G1 < 7.2 G2 < 3.6 G3); in contrast S CNAs significantly increased in G3 (0.7 G1 < 3.7 G2 < 7.0 G3). Interestingly, we observed several intra-chromosomal rearrangements in G3 tumors on chromosomes not usually involved in NB. Excluding MYCN amplified tumors by G3 we found a high frequency of S CNAs in this group. Gene expression analysis showed a deregulation of downstream genes of Ras and Rho signaling pathway among the 3 groups. It has been also observed a progressive switch off of development and adhesion genes and a switch on of cell cycle genes from G1 to G2 to G3. Moreover, the telemorase genes were significantly expressed in G3 with respect to remaining groups. Present data show an accumulation of S CNAs from stage 4S to 4. The deregulation of genes Rho/Ras pathway may explain the increase of tumor aggressiveness from G1 to G2 to G3. The increase of cell cycle and telomerase genes expression associated with G3 would provide unlimited replicative potential for these tumors and may be responsible for accumulation of S CNAs. Finally, we can argue that accumulation of structural aberrations and gene deregulation is age-dependent and it is associated with a more aggressive tumor phenotype. We analyzed 133 samples of metastatic neuroblastoma from patients divided into three groups: G1 49 patients stage 4S and MYCN single copy; G2 37 patients stage 4 younger than 18 months of age at diagnosis, MYCN single copy with no disease progression; G3 47 patients stage 4 older than 19 months of age at diagnosis, with unfavorable outcome.

Project description:MYCN is an oncogene amplified in approximately 20% of all neuroblastomas and 50% of high risk neuroblastoma. It is a transcription factor regulating the expression of genes involved in proliferation and apoptosis.We would like to identify genes potentially regulated by MYCN in a conditional MYCN expression system. The SHEP Tet21N system is a conditional, tetracycline-regulated MYCN expression system established in the MYCN non-amplified SHEP neuroblastoma cell line (Lutz et al., 1996). Expression of MYCN is switched off by the addition of tetracycline to the growth medium. Levels of MYCN protein and RNA in the absence of tetracycline are comparable with those present in MYCN amplified cell lines (Bell et al., 2006). By performing microarray analyses on the Tet21n cell lines in the presence and absence of MYCN we hope to identify genes whose expression had been altered by MYCN either upregulated or downregulated and may be potential MYCN targets. The altered expression of some of these genes will then be validated using quantitative RTPCR and a selection will be further investigated to determine if they are MYCN transcriptional targets and may be potential candidates for anti-MYCN therapies for neuroblastoma Specific objectives 1) To investigate genes which are altered by 2 fold or more in the presence of or absence of MYCN in Tet21N cells. Refs: Bell, E., Premkumar, R., Carr, J., Lu, X., Lovat, P.E., Kees, U.R., Lunec, J. & Tweddle, D.A. (2006). The role of MYCN in the failure of MYCN amplified neuroblastoma cell lines to G1 arrest after DNA damage. Cell Cycle, 5, 2639-47. Lutz, W., Stohr, M., Schurmann, J., Wenzel, A., Lohr, A. & Schwab, M. (1996). Conditional expression of N-myc in human neuroblastoma cells increases expression of alpha-prothymosin and ornithine decarboxylase and accelerates progression into S-phase early after mitogenic stimulation of quiescent cells. Oncogene, 13, 803-12.

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SNRPD3 preserves balanced MYCN-driven alternate splicing and represents a therapeutic vulnerability in neuroblastoma

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