Effect of cytotoxic agents and retinoic acid on Myc-N protein expression in neuroblastoma

Therapy resistance in neuroblastoma: Mechanisms and reversal strategies

Neuroblastoma is one of the most common pediatric solid tumors that threaten the health of children, accounting for about 15% of childhood cancer-related mortality in the United States. Currently, multiple therapies have been developed and applied in clinic to treat neuroblastoma including chemotherapy, radiotherapy, targeted therapy, and immunotherapy. However, the resistance to therapies is inevitable following long-term treatment, leading to treatment failure and cancer relapse. Hence, to understand the mechanisms of therapy resistance and discover reversal strategies have become an urgent task. Recent studies have demonstrated numerous genetic alterations and dysfunctional pathways related to neuroblastoma resistance. These molecular signatures may be potential targets to combat refractory neuroblastoma. A number of novel interventions for neuroblastoma patients have been developed based on these targets. In this review, we focus on the complicated mechanisms of therapy resistance and the potential targets such as ATP-binding cassette transporters, long non-coding RNAs, microRNAs, autophagy, cancer stem cells, and extracellular vesicles. On this basis, we summarized recent studies on the reversal strategies to overcome therapy resistance of neuroblastoma such as targeting ATP-binding cassette transporters, MYCN gene, cancer stem cells, hypoxia, and autophagy. This review aims to provide novel insight in how to improve the therapy efficacy against resistant neuroblastoma, which may shed light on the future directions that would enhance the treatment outcomes and prolong the survival of patients with neuroblastoma.

Differentiating Neuroblastoma: A Systematic Review of the Retinoic Acid, Its Derivatives, and Synergistic Interactions

A neuroblastoma (NB) is a solid paediatric tumour arising from undifferentiated neuronal cells. Despite the recent advances in disease management and treatment, it remains one of the leading causes of childhood cancer deaths, thereby necessitating the development of new therapeutic agents and regimens. Retinoic acid (RA), a vitamin A derivative, is a promising agent that can induce differentiation in NB cells. Its isoform, 13-cis RA or isotretinoin, is used in NB therapy; however, its effectiveness is limited to treating a minimal residual disease as maintenance therapy. As such, research focuses on RA derivatives that might increase the anti-NB action or explores the potential synergy between RA and other classes of drugs, such as cellular processes mediators, epigenetic modifiers, and immune modulators. This review summarises the in vitro, in vivo, and clinical data of RA, its derivatives, and synergising compounds, thereby establishing the most promising RA derivatives and combinations of RA for further investigation.

MYCN is amplified during S phase, and c‑myb is involved in controlling MYCN expression and amplification in MYCN‑amplified neuroblastoma cell lines

Neuroblastoma derived from primitive sympathetic neural precursors is a common type of solid tumor in infants. MYCN proto-oncogene bHLH transcription factor (MYCN) amplification and 1p36 deletion are important factors associated with the poor prognosis of neuroblastoma. Expression levels of MYCN and c-MYB proto-oncogene transcription factor (c-myb) decline during the differentiation of neuroblastoma cells; E2F transcription factor 1 (E2F1) activates the MYCN promoter. However, the underlying mechanism of MYCN overexpression and amplification requires further investigation. In the present study, potential c-Myb target genes, and the effect of c-myb RNA interference (RNAi) on MYCN expression and amplification were investigated in MYCN-amplified neuroblastoma cell lines. The mRNA expression levels and MYCN gene copy number in five neuroblastoma cell lines were determined by quantitative polymerase chain reaction. In addition, variations in potential target gene expression and MYCN gene copy number between pre- and post-c-myb RNAi treatment groups in MYCN-amplified Kelly, IMR32, SIMA and MHH-NB-11 cell lines, normalized to those of non-MYCN-amplified SH-SY5Y, were examined. To determine the associations between gene expression levels and chromosomal aberrations, MYCN amplification and 1p36 alterations in interphases/metaphases were analyzed using fluorescence in situ hybridization. Statistical analyses revealed correlations between 1p36 alterations and the expression of c-myb, MYB proto-oncogene like 2 (B-myb) and cyclin dependent kinase inhibitor 1A (p21). Additionally, the results of the present study also demonstrated that c-myb may be associated with E2F1 and L3MBTL1 histone methyl-lysine binding protein (L3MBTL1) expression, and that E2F1 may contribute to MYCN, B-myb, p21 and chromatin licensing and DNA replication factor 1 (hCdt1) expression, but to the repression of geminin (GMNN). On c-myb RNAi treatment, L3MBTL1 expression was silenced, while GMNN was upregulated, indicating G₂/M arrest. In addition, MYCN gene copy number increased following treatment with c-myb RNAi. Notably, the present study also reported a 43.545% sequence identity between upstream of MYCN and Drosophila melanogaster amplification control element 3, suggesting that expression and/or amplification mechanisms of developmentally-regulated genes may be evolutionarily conserved. In conclusion, c-myb may be associated with regulating MYCN expression and amplification. c-myb, B-myb and p21 may also serve a role against chromosome 1p aberrations. Together, it was concluded that MYCN gene is amplified during S phase, potentially via a replication-based mechanism.

Neural crest and cancer: Divergent travelers on similar paths

Neural crest cells are multipotent progenitors that dynamically interpret diverse microenvironments to migrate significant distances as a loosely associated collective and contribute to many tissues in the developing vertebrate embryo. Uncovering details of neural crest migration has helped to inform a general understanding of collective cell migration, including that which occurs during cancer metastasis. Here, we discuss several commonalities and differences of neural crest and cancer cell migration and behavior. First, we focus on some of the molecular pathways required for the initial specification and potency of neural crest cells and the roles of many of these pathways in cancer progression. We also describe epithelial-to-mesenchymal transition, which plays a critical role in initiating both neural crest migration and cancer metastasis. Finally, we evaluate studies that demonstrate myriad forms of cell-cell and cell-environment communication during neural crest and cancer collective migration to highlight the remarkable similarities in their molecular and cell biological regulation.

Combination of 13 cis-retinoic acid and tolfenamic acid induces apoptosis and effectively inhibits high-risk neuroblastoma cell proliferation

Chemotherapeutic regimens used for the treatment of Neuroblastoma (NB) cause long-term side effects in pediatric patients. NB arises in immature sympathetic nerve cells and primarily affects infants and children. A high rate of relapse in high-risk neuroblastoma (HRNB) necessitates the development of alternative strategies for effective treatment. This study investigated the efficacy of a small molecule, tolfenamic acid (TA), for enhancing the anti-proliferative effect of 13 cis-retinoic acid (RA) in HRNB cell lines. LA1-55n and SH-SY5Y cells were treated with TA (30μM) or RA (20μM) or both (optimized doses, derived from dose curves) for 48h and tested the effect on cell viability, apoptosis and selected molecular markers (Sp1, survivin, AKT and ERK1/2). Cell viability and caspase activity were measured using the CellTiter-Glo and Caspase-Glo kits. The apoptotic cell population was determined by flow cytometry with Annexin-V staining. The expression of Sp1, survivin, AKT, ERK1/2 and c-PARP was evaluated by Western blots. The combination therapy of TA and RA resulted in significant inhibition of cell viability (p<0.0001) when compared to individual agents. The anti-proliferative effect is accompanied by a decrease in Sp1 and survivin expression and an increase in apoptotic markers, Annexin-V positive cells, caspase 3/7 activity and c-PARP levels. Notably, TA+RA combination also caused down regulation of AKT and ERK1/2 suggesting a distinct impact on survival and proliferation pathways via signaling cascades. This study demonstrates that the TA mediated inhibition of Sp1 in combination with RA provides a novel therapeutic strategy for the effective treatment of HRNB in children.

Micro-RNA-21 regulates the sensitivity to cisplatin in human neuroblastoma cells

BACKGROUND/PURPOSE

Drug resistance often causes treatment failure in neuroblastomas. Increasing evidence has implicated that the micro-RNAs (miRNAs) are involved in the development of drug resistance. In this report, we aimed to investigate the role of miRNA in cisplatin resistance of neuroblastoma cells.

MATERIALS AND METHODS

The cell viability of the neuroblastoma cells after cisplatin treatment was analyzed. The expression of the miRNAs and phosphatase and tensin homolog (PTEN) messenger RNA in the neuroblastoma cells was studied by real-time polymerase chain reaction. Overexpression of miRNA or suppression of miRNA expression by antagomir was used to investigate the effects of miRNA on the cisplatin-induced cell death or proliferation.

RESULTS

The expression of miR-21 was increased in the cisplatin-resistant (CisR) neuroblastoma cells as compared with the parental cells, and the antagomir against miR-21 converted the resistant cells into sensitive ones. Ectopic expression of pre-miR-21 in parental cells resulted in decreased sensitivity to cisplatin treatment. In addition, overexpression of pre-miR-21 markedly increa sed the proliferation rate of neuroblastoma cells. The level of PTEN messenger RNA and protein in the CisR cells was lower than that in the parental cells. Transfection of pre-miR-21 into the parental cells reduced the PTEN expression, and transfection of anti-miR-21 into the CisR cells increased the PTEN expression.

CONCLUSION

Micro-RNA-21 regulated the drug resistance and proliferation in neuroblastoma cells.

Protective effects of acetyl-L-carnitine on cisplatin cytotoxicity and oxidative stress in neuroblastoma

The most widely used platinum-derived drug is cisplatin in neuroblastoma (NB) chemotherapy, which is severely neurotoxic. Acetyl-L-Carnitine (ALC) is a natural occurring compound with a neuroprotective activity in several experimental paradigms. The aim of this study was to determine the effects of ALC on cisplatin induced cytotoxicity and oxidative stress in NB cells. SH-SY5Y (N-Myc negative) and KELLY (N-Myc positive) human NB cell lines were used. Cisplatin induced apoptosis was assessed by using a Cell Death Detection ELISA(PLUS) kit. Lipid peroxidation levels were determined by HPLC analysis. Glutathione levels were determined spectrophotometrically. ALC was used prophylactic or after cisplatin application. The level of cisplatin doses were determined in both type of NB cells at which 50% cell death occurred along with synchronized apoptosis induced. Prophylactic 10 and 50 micromol of ALC concentrations were decreased cisplatin induced lipid peroxidation compared to controls that normally exhibited apoptosis especially in SH-SY5Y cells. Cisplatin caused oxidative stress through decreasing glutathione levels in both cell types. ALC were effectively inhibited the increase in cisplatin induced oxidized glutathione and lipid peroxidation formation in NB cells. We suggested that prophylactic ALC would be a useful agent for cisplatin induced toxicity in NB cells.