Targeting of G-Quadruplex Harboring Pre-miRNA 92b by LNA Rescues PTEN Expression in NSCL Cancer Cells.

Since the elevated levels of microRNAs (miRNAs) often cause various diseases, selective inhibition of miRNA maturation is an important therapeutic strategy. Commonly used anti-miRNA strategies are limited to targeting of mature miRNAs, as the upstream targeting of miRNA maturation with an oligonucleotide is challenging due to the presence of a stable pre-miRNA stem-loop structure. Previously, we reported that about 16% of known human pre-miRNAs have the potential to adopt G-quadruplex (GQ) structures alternatively to canonical stem-loops. Herein, we showed that a rationally designed locked nucleic acid (LNA) binds specifically the GQ conformation of pre-miRNA 92b and inhibits pre-miRNA maturation. Further, we showed that the LNA treatment rescues PTEN expression in non-small-cell lung cancer (NSCLC) cells, which is suppressed by the elevated level of miRNA 92b. Treatment of LNA significantly decreases the IC50 of doxorubicin for NSCLC cells. This strategy can be developed as a novel anti-miRNA therapeutic approach to target GQ harboring miRNAs. This can potentially be a more powerful approach than targeting of the mature miRNA, as it is an upstream targeting and can reduce both 3' and the 5' mature miRNA levels at once.