Efficient in vivo microRNA targeting of liver metastasis.

Targeting oncogenic microRNAs (miRNAs) is emerging as a promising strategy for cancer therapy. In this study, we provide proof of principle for the safety and efficacy of miRNA targeting against metastatic tumors. We tested the impact of targeting miR-182, a pro-metastatic miRNA frequently overexpressed in melanoma, the in vitro silencing of which represses invasion and induces apoptosis. Specifically, we assessed the effect of anti-miR-182 oligonucleotides synthesized with 2' sugar modifications and a phosphorothioate backbone in a mouse model of melanoma liver metastasis. Luciferase imaging showed that mice treated with anti-miR-182 had a lower burden of liver metastases compared with control. We confirmed that miR-182 levels were effectively downregulated in the tumors of anti-miR-treated mice compared with tumors of control-treated mice, both in the liver and in the spleen. This effect was accompanied by an upregulation of multiple miR-182 direct targets. Transcriptional profiling of tumors treated with anti-miR-182 or with control oligonucleotides revealed an enrichment of genes controlling survival, adhesion and migration modulated in response to anti-miR-182 treatment. These data indicate that in vivo administration of anti-miRs allows for efficient miRNA targeting and concomitant upregulation of miRNA-controlled genes. Our results demonstrate that the use of anti-miR-182 is a promising therapeutic strategy for metastatic melanoma and provide a solid basis for testing similar strategies in human metastatic tumors.