Cancer cell-specific RNA interference in vivo

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RNA interference (RNAi) caused by small interfering RNAs (siRNAs) is a general method of sequence-specific control of gene expression in cells, both in vitro and in vivo. A problem of design of siRNAs for every gene of interest can be solved in silico by bioinformatics and validated in a limited number of experiments in vitro and in vivo. Therefore, development of siRNA-based drugs can potentially be less time-consuming and costly than that of classical drugs and can further promote development of personalized medicine. Recent breakthrough in delivery of siRNAs in vivo enabled the initiation of a number of clinical trials with siRNA-based drugs (treatment of hyperlipidemia, age related macular degeneration, etc.), some of which reached advanced stages (e.g. TTR amyloidosis). However, despite these important successes in the field, cancer-cell specific delivery/activation of siRNAs still remains a problem, for which no simple and general solution is known. Therefore, the number of targets for siRNA drugs is limited to genes, which are either strongly overexpressed or present exclusively in cancer cells. Application of cancer-specific prodrugs is expected to not only extend the number of possible targets for siRNA drug, but also reduce side effects of the treatment. In this project we will work on a simple solution for designing cancer specific siRNA-prodrugs, which are activated in the presence of reactive oxygen species (ROS). The cell specificity will be based on the experimental fact that cancer cells overproduce ROS, whereas their concentration in normal cells is negligible. ROS-induced activation is a potential general approach for the design of cancer specific siRNAs, since elevated ROS is believed to be crucial for cancer phenotypes. Therefore, the proposed siRNA-prodrugs should be active against many different cancer types. As a proof-of-principle, ROS-responsive siRNA-prodrugs targeting Ubr ligases will be developed and tested in the treatment of hepatocellular carcinoma (HCC) in mice models. This model was selected since no satisfactory treatment for HCC is currently known. Moreover, methods of liver specific delivery of siRNAs are well developed. The principles, worked out in this project, will be potentially applicable towards the design of siRNA-prodrugs for the treatment of cancers in organs other than the liver, providing that organ-specific delivery will become available in the future. This study capitalizes on the extensive experience of (a) the group of Mokhir in synthesis and cellular applications of “caged” siRNAs and (b) the group of Zatsepin on optimization of siRNA design and formulation as well synthesis and application of siRNA-based conjugates for inhibition of gene expression in vivo in mice models.