Apoptosis induction by antisense oligonucleotides against miR-17-5p and miR-20a in lung cancers overexpressing miR-17-92

Amplification and overexpression of the miR- 17- 92 microRNAs ( miRNA) cluster at 13q31.3 has recently reported, with pointers to functional involvement in the development of B- cell lymphomas and lung cancers. In the present study, we show that inhibition of miR- 17- 5p and miR- 20a with antisense oligonucleotides ( ONs) can induce apoptosis selectively in lung cancer cells overexpressing miR- 17- 92, suggesting the possibility of 'Oncomi R addiction to expression of these miRNAs in a subset of lung cancers. In marked contrast, antisense ONs against miR-18a and miR- 19a did not exhibit such inhibitory effects, whereas inhibition of miR-92-1 resulted in only modest reduction of cell growth, showing significant distinctions among miRNAs of the miR- 17- 92 cluster in terms of their roles in cancer cell growth. During the course of this study, we also found that enforced expression of a genomic region, termed C2, residing 30 to miR- 17- 92 in the intron 3 of C13orf25 led to marked growth inhibition in association with double stranded RNA- dependent protein kinase activation. Finally, this study also revealed that the vast majority of C13orf25 transcripts are detected as Drosha- processed cleavage products on Northern blot analysis and that a novel polyadenylation site is present 30 to the miR- 17- 92 cluster and 50 to the C2 region. Taken together, the present findings contribute towards better understanding of the oncogenic roles of miR- 17- 92, which might ultimately lead to the future translation into clinical applications.