MiRNA hijacking for self-modulating oligonucleotide therapy

Due to a pivotal role in the post-transcriptional regulation of gene expressions implicated in numerous human diseases, miRNAs have been positioned to serve as promising disease biomarkers and novel therapeutic targets. However, gene silencing by miRNAs is limited to transcripts that contain complementary sequences. Herein we describe a miRNA-hijacker capable of downregulating newly assigned target mRNAs by hijacking intended miRNA. We developed a linear miRNA-hijacker with two miRNA binding sites to achieve higher repression and a hairpin-type (HT) miRNA-hijacker gifted with the hidden target mRNA binding site to minimize off-target effects. We also verified that the repression process by the miRNA-hijacker essentially involves the active mediating miRNA and functional AGO-RISC complex. By engineering the miRNA-hijackers to downregulate the anti-apoptotic BCL-xL gene, we successfully induced apoptosis only in the breast cancer cells overexpressing specific miRNAs and further validated its therapeutic efficacy in vivo, significantly reducing the tumor volume of the xenograft mouse upon its tail-vein injection. Our miRNA-hijacker technology can establish a new platform for self-modulating oligonucleotide therapy by hijacking disease-associated miRNAs and changing their destinations Overall design: We transfected hairpin-structured miRNA-hijacker targeting PKR gene into HeLa cells overexpressing miR-141 (HeLa-141) and investigated differentially expressed genes.