MiRNAs and oncolytic adenovirus potenc

Exploiting miRNA to enhance oncolytic adenovirus potency

J.W.H. van Ginkel1, C. Vermeulen2, J. Hodzic2, R.W.D. Kleinendorst2, A. Vermeulen3, J. Karpilow3, J.J.M. Meulenberg1, V.W. van Beusechem1,2
1ORCA Therapeutics, Amsterdam, The Netherlands; 2Department of Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands; 3Thermo Fisher Scientific, Dharmacon RNAi Technologies, Lafayette, CO, USA.

Oncolytic adenoviruses represent a novel class of anticancer agents, designed to selectively replicate in tumor cells and to destroy these cells by inducing oncolysis. In recent years, it has become evident that viruses and their host cells interact vice versa via microRNA (miRNA). In cancer cells, miRNA expression is generally reduced compared to normal cells. We envisioned that host miRNA expression might influence adenovirus propagation and that the miRNAs involved could be deregulated in cancer cells. To investigate this, we performed functional screens on PC-3 prostate cancer cells using Thermo Scientific Dharmacon miRIDIAN miRNA mimic and inhibitor libraries, representing 344 unique mature miRNAs. We identified miRNAs that selectively sensitized PC-3 cells to adenovirus-induced cell death, without compromising adenovirus propagation. We chose 5 miRNAs to develop more effective cancer therapies with oncolytic adenoviruses based on validation experiments in three different cancer cell lines. In parallel, a format for efficient miRNA expression from the oncolytic adenovirus genome was designed. Using a primary miRNA expression cassette, proof-of-principle was demonstrated: the virus-expressed miRNA induced knock down of an endogenous target at the protein level during lytic replication of the adenovirus in cancer cells. We then constructed new oncolytic adenoviruses expressing lead miRNAs and confirmed that they expressed mature miRNAs. Using an artificial Luciferase based readout system, efficient target knock-down was demonstrated for one of the lead miRNAs within 24 hours after virus infection. Analysis of relative cancer cell killing potency compared to control viruses in relevant experimental models will be subject of further investigation.