[Role and mechanism of cysteine and glycine-rich protein 2 in the malignant progression of neuroblastoma].

OBJECTIVE: To investigate the function and underlying mechanism of cysteine and glycine-rich protein 2 (CSRP2) in neuroblastoma (NB). METHODS: The correlation between the expression level of CSRP2 mRNA and the prognosis of NB children in NB clinical samples was analyzed in R2 Genomics Analysis and Visualization Platform. The small interfering RNA (siRNA) targeting CSRP2 or CSRP2 plasmid were transfected to NB cell lines SK-N-BE(2) and SH-SY5Y. Cell proliferation was observed by crystal violet staining and real-time cellular analysis. The ability of colony formation of NB cells was observed by colony-forming unit assay. Immunofluorescence assay was used to detect the expression of the proliferation marker Ki-67. Flow cytometry analysis for cell cycle proportion was used with cells stained by propidium iodide (PI). Annexin V/7AAD was used to stain cells and analyze the percentage of cell apoptosis. The ability of cell migration was determined by cell wound-healing assay. The level of protein and mRNA expression of CSRP2 in NB primary tumor and NB cell lines were detected by Western blot and quantitative real-time PCR (RT-qPCR). RESULTS: By analyzing the NB clinical sample databases, it was found that the expression levels of CSRP2 in high-risk NB with 3/4 stages in international neuroblastoma staging system (INSS) were significantly higher than that in low-risk NB with 1/2 INSS stages. The NB patients with high expression levels of CSRP2 were shown lower overall survival rate than those with low expression levels of CSRP2. We detected the protein levels of CSRP2 in the NB samples by Western blot, and found that the protein level of CSRP2 in 3/4 INSS stages was significantly higher than that in 1/2 INSS stages. Knockdown of CSRP2 inhibited cell viability and proliferation of NB cells. Overexpression of CSRP2 increased the proliferation of NB cells. Flow cytometry showed that the proportion of sub-G1, G0/G1 and S phase cells and Annexin V positive cells were increased after CSRP2 deficiency. In the cell wound-healing assay, the healing rate of NB cells was significantly attenuated after knockdown of CSRP2. Further mechanism studies showed that the proportion of the proliferation marker Ki-67 and the phosphorylation levels of extracellular signal-regulated kinases 1/2 (ERK1/2) were significantly decreased after CSRP2 knockdown. CONCLUSION: CSRP2 is highly expressed in high-risk NB with 3/4 INSS stages, and the expression levels of CSRP2 are negatively correlated with the overall survival of NB patients. CSRP2 significantly increased the proliferation and cell migration of NB cells and inhibited cell apoptosis via the activation of ERK1/2. All these results indicate that CSRP2 promotes the progression of NB by activating ERK1/2, and this study will provide a potential target for high-risk NB therapy.

TAF1D promotes proliferation by transcriptionally activating G2/M phase-related genes in MYCN-amplified neuroblastoma.

High-risk neuroblastoma (HR-NB) is an aggressive childhood cancer that responds poorly to currently available therapies and is associated with only about a 50% 5-year survival rate. MYCN amplification is a critical driver of these aggressive tumors, but so far there have not been any approved treatments to effectively treat HR-NB by targeting MYCN or its downstream effectors. Thus, the identification of novel molecular targets and therapeutic strategies to treat children diagnosed with HR-NB represents an urgent unmet medical need. Here, we conducted a targeted siRNA screening and identified TATA box-binding protein-associated factor RNA polymerase I subunit D, TAF1D, as a critical regulator of the cell cycle and proliferation in HR-NB cells. Analysis of three independent primary NB cohorts determined that high TAF1D expression correlated with MYCN-amplified, high-risk disease and poor clinical outcomes. TAF1D knockdown more robustly inhibited cell proliferation in MYCN-amplified NB cells compared with MYCN-non-amplified NB cells, as well as suppressed colony formation and inhibited tumor growth in a xenograft mouse model of MYCN-amplified NB. RNA-seq analysis revealed that TAF1D knockdown downregulates the expression of genes associated with the G2/M transition, including the master cell-cycle regulator, cell-cycle-dependent kinase 1 (CDK1), resulting in cell-cycle arrest at G2/M. Our findings demonstrate that TAF1D is a key oncogenic regulator of MYCN-amplified HR-NB and suggest that therapeutic targeting of TAF1D may be a viable strategy to treat HR-NB patients by blocking cell-cycle progression and the proliferation of tumor cells.