MicroRNAs (miRNAs) are small noncoding RNAs, thought to be involved in physiologic and developmental processes by negatively regulating expression of target genes. We have previously reported frequent down-regulation of the let-7 miRNA family in lung cancers and, in the present study, assessed alteration in a panel of 19 lung cancer cell lines. As a result, we found for the first time that the miR-17-92 cluster, which comprises seven miRNAs and resides in intron 3 of the C13or f 25 gene at 13q31.3, is markedly overexpressed in lung cancers, especially with small-cell lung cancer histology. Southern blot analysis revealed the presence of increased gene copy numbers of the miRNA cluster in a fraction of lung cancer cell lines with overexpression. In addition, we were able to show predominant localization of C13orf 25 transcripts within the nucleus and introduction of the expression construct of the miR-17-92 cluster, but not the putative open reading frame of C13orf 25, enhancing lung cancer cell growth. These findings clearly suggest that marked overexpression of the miR-17-92 cluster with occasional gene amplification may play a role in the development of lung cancers, especially in their most aggressive form, small-cell lung cancer, and that the C13orf 25 gene may well be serving as a vehicle in this regard. (Cancer Res 2005; 65(21): 9628-32)

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 'OncomiR addiction' to expression of these miRNAs in a subset of lung cancers. In marked contrast, antisense ONs against miR18a 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 3 0 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 3 0 to the miR-17-92 cluster and 5 0 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.

microRNAs (miRNA) are small, endogenously expressed non-coding RNAs that are sequentially processed by Drosha and Dicer from primary transcripts, by negatively regulating the expression of protein-coding genes through either translational repression or RNA degradation. Their expression patterns are developmentally regulated and/or tissue specific, while altered expressions of certain miRNAs are frequently observed in human cancers, though the underlying regulatory mechanism is largely unknown. Herein, we show that Dicer expression was inversely correlated with expression levels of mature let-7 in a panel of human cancer cell lines, showing association with cell growth and cell cycle phases. Overexpression of let-7 significantly reduced the expression of Dicer at both the protein and messenger RNA levels, whereas antisense-mediated reduction of let-7 expression conversely increased Dicer at both levels. A luciferase assay using a reporter carrying a putative target site in the 3' untranslated region of Dicer revealed that let-7 directly affects Dicer expression. Downregulation of Dicer resulted in a reduced expression of mature let-7. Furthermore, overexpression of let-7 decreased the levels of expression of other mature miRNAs, while knockdown of let-7 increased those levels. Taken together, these findings strongly suggest the possible existence of a novel regulatory loop, in which let-7 may play a role as a key miRNA for implementing the tightly regulated, equilibrated state of Dicer and various miRNAs.

Small-molecule nociceptin antagonists were synthesized to examine their therapeutic potential. After a 4-aminoquinoline derivative was found to bind with the human ORL(1) receptor, a series of 4-aminoquinolines and related compounds were synthesized and their binding was evaluated. Elucidation of structure-activity relationships eventually led to the optimum compounds. One of these compounds, N-(4-amino-2-methylquinolin-6-yl)-2-(4-ethylphenoxymethyl)benzamide hydrochloride (11) not only antagonized nociceptin-induced allodynia in mice but also showed analgesic effect in a hot plate test using mice and in a formalin test using rats. Its analgesic effect was not antagonized by the opioid antagonist naloxone. These results indicate that this nociceptin antagonist has the potential to become a novel type of analgesic that differs from mu-opioid agonists.

1 Pharmacological eects of a novel opioid receptor-like1 (ORL 1 ) receptor antagonist, [N-(4-amino-2-methylquinolin-6-yl)-2-(4-ethylphenoxymethyl) benzamide monohydrochloride] (JTC-801), were examined in in vitro and in vivo. We have demonstrated that JTC-801 antagonizes the ORL 1 receptor response, and that JTC-801 has ecacious and potent anti-nociceptive eects in acute pain animal models not only by intravenous injection but also oral administration. These results suggest that JTC-801 may represent a new class of analgesics.