Abstract 1459: miR-221: A potential therapeutic target for hepatocellular carcinoma

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA microRNAs, which control post-transcriptional gene expression by repressing mRNA translation and/or causing mRNA degradation, play important roles in human cancers. miR-221 is one of the two microRNAs in the miR-221/222 cluster located in chromosome-X, targets key cancer pathways and inhibit translation of several tumor suppressors including p27, p57, and PTEN. miR-221 is up-regulated by >2-fold in 55% and >5-fold in 14% of human hepatocellular carcinoma (HCC) tumor samples. Importantly, it has been shown in preclinical HCC models that miR-221 overexpression accelerated tumorigenesis, while miR-221 inhibition reduced tumor growth. To identify novel microRNA antagonists that specifically inhibit miR-221 (refer to as miR-221 anti-miRs) for the treatment of HCC, we have generated a number of chemically-modified oligonucleotides and screened for their ability to inhibit miR-221 functions. A number of potent and metabolically stable miR-221 anti-miRs devoid of proinflammatory potential were identified. These miR-221 anti-miRs were tested in a number of human HCC cell lines that highly express miR-221 compare to normal adult human hepatocytes. We demonstrated the de-repression of both p27 mRNA and p27 protein in HCC cells following treatment with miR-221 anti-miRs. We also showed in HCC cells the de-repression of a novel miR-221 target gene recently identified through an argonuate pull-down assay (Ago-IP), alongside with the enrichment of global miR-221 target seeds (as defined by TargetScan) following miR-221 anti-miRs treatment. We then sought to determine the biologic consequences following miR-221 inhibition in HCC cells. In standard cell proliferation assays, we demonstrated that HCC cells responded to miR-221 anti-miRs treatment with IC50s of 125 to 500nM under free-uptake conditions and IC50s of 5 to 75 nM under transfection conditions. In addition, we also showed that miR-221 anti-miRs treatment disrupted HCC cell cycle transition. Altogether, our data showed that miR-221 inhibition de-repressed p27, blocked cell cycle progression and reduced cell proliferation in HCC cells, and supports the notion of miR-221 as a potential therapeutic target for the treatment of HCC. Further preclinical testing of our miR-221 anti-miRs is currently in progress. Citation Format: Edmund C. Lee, Jessica Xu, Thomas Vincent, Jie Chen, Michael Nelson, Xinqiang Huang, Eric Marcusson, John Androsavich, Scott Davis, Adam Pavlicek, Neil Gibson, Sonya Zabludoff. miR-221: A potential therapeutic target for hepatocellular carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1459. doi:10.1158/1538-7445.AM2014-1459