MicroRNA-506-3p as a Differentiation Agent for Neuroblastoma
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Neuroblastoma is the most common solid tumor cancer in infants less than 1 year of age, and the second most common extracranial cancer in children. Approximately 60% of the cases have already spread to the lymph nodes at diagnosis, where children with this disease typically do not live past 10 years of age. The high mortality rate of this cancer arises from the failure of neural crest cell precursors to differentiate, which inhibits the maturation of these cells, leaving immortal, infant malignancies. 13-cis-retionoic acid is currently used as the agent of choice for neuroblastoma, but exhibits a 50% recurrence of tumor cells, leaving the identification of new targets a crucial step in the elucidation of neuroblastoma.
MicroRNAs are small, noncoding RNAs, that regulate transcription and the expression of many genes. They perform posttranscriptional gene modification by translational suppression, mRNA degradation, or site-specific cleavage of mRNAs. The dysregulation of these molecules leads to tumor development and metastasis, along with chemoresistance and multidrug resistance. MicroRNA mimics are partially double-stranded RNAs designed to mimic the function of endogenous miRNAs, effectively increasing the level of cellular miRNAs. Recent studies have provided evidence for the use of miRNAs in the induction of differentiation of neuroblastoma cells, which induce malignant cells to mature and undergo apoptosis. More recently, a novel miRNA, miR-506-3p, was identified as a potent inducer of neuroblastoma cell differentiation by the down-regulation of two target genes at the 3’UTR target site, suggesting this as an effective differentiation agent for neuroblastomal remission therapy.
The current study examined the effects of retinoic acid and miR-506-3p mimic, alone and in combination, on undifferentiated neuroblastoma cells. To approach this, techniques such as cell culture, forward and reverse transfection, neurite outgrowth assays, cell viability assays, cell proliferation assays, and Western Blot were used to quantify the differentiation-inducing effect of these treatments. For both all-trans-retinoic acid (ATRA) and microRNA-506-3p mimic-treated cells with different genetic backgrounds, there were variations in the responses. More cell lines responded to the miR-506-3p mimic, indicating the possibility of a more generic effect than ATRA on neuroblastoma cell differentiation. For combined treatments, all experimental values were less than predicted. In sum, the results provided here support the hypothesis that the miR-506-3p mimic may have a more generic effect than ATRA on neuroblastoma cell differentiation, but we cannot report synergism for the response following combined treatments on neuroblastoma cell viability. However, an enhanced effect for the combined treatments was observed.