Development of Shortened miR-506-3p Mimics Exhibiting Strong Differentiation-Inducing Activity in Neuroblastoma Cells

microRNA mimics are synthetic RNA molecules that imitate the mature miRNA duplexes and their functions. These mimics have shown promise in treating cancers. Nucleotide chemical modifications of microRNA mimics have been investigated and have improved the stability of miRNA mimics. However, the potential therapeutic benefit of mimic analogs based on sequence modifications has not been explored. miR-506-3p was identified as a differentiation-inducing microRNA in neuroblastoma cells, suggesting the potential of applying the miR-506-3p mimic in neuroblastoma differentiation therapy. In this study, we explored the possibility of developing shortened miR-506-3p analogs that can maintain differentiation-inducing activities comparable to the wild-type miR-506-3p mimic. We found that deleting up to two nucleotides at either the 3′ end or within the middle region of the miR-506-3p sequence fully maintained the differentiation-inducing activity when compared to the wild-type mimic. Deleting up to four nucleotides from the 3′ end or deleting three nucleotides in the middle positions diminished the differentiation-inducing activity, but the analogs still maintained differentiation-inducing activities that were significantly higher than the negative control oligo. The shortened analog designs potentially benefit patients from two perspectives: (1) the reduced cost of manufacturing shortened analogs, and (2) the reduced non-specific toxicity due to their smaller molecular sizes.