Name: genome-wide rnai screening to identify host factors that modulate oncolytic virus therapy
Uploaded: 2018-04-03T13:00:00
Description: Watch this Scientific Journal Video about Genome-wide RNAi Screening to Identify Host Factors That Modulate Oncolytic Virus Therapy at JoVE.com

This work was supported by grants from the Ontario Institute for Cancer Research, the Canada Foundation for Innovation, the Ottawa Regional Cancer Foundation, and the Terry Fox Research Institute. K.J.A. was supported by a Vanier Canada Graduate Scholarship, a Canadian Institute for Health Research-Master&#39;s Award, and an Ontario Graduate Scholarship.

1. Development and validation of a high-throughput siRNA screening assay
NOTE: For all experiments, use Hepes-buffered growth media appropriate for each cell line. See Figure 1 for an overview of the workflow from assay optimization to tertiary validation.
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	<li>Determination of the optimal transfection conditions
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		<li>Select a tumor cell line or ideally multiple tumor cells lines with which to optimize transfection conditions (e....

<ol>
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Here we present a protocol for employing high-throughput RNAi screening to identify host targets that can be manipulated to enhance oncolytic virus therapy. This has been tested successfully with oncolytic Maraba virus and oncolytic vaccinia virus, but, as noted, it can be adapted for use with other oncolytic viruses or other viruses generally to identify host genes that modulate virus replication. The screening protocol is also designed to identify genes that increase or decrease spread, but it can be readily modified f...

High-throughput genome-wide RNAi screening has proven to be an invaluable tool for revealing biological insights in diverse areas of study including virus biology. Over the past decade or so, numerous groups have undertaken cell-based large-scale RNAi screening to extensively identify host genes that modulate virus replication (Reviewed in1,2,3,4,5,6,7). Interestingly, a large number of these screens have been conducted in cancer cells and several with viruses that are current oncolytic virus candidates including vaccinia virus8,9,10, Myxoma virus11, herpes simplex virus12, vesicular stomatitis virus13,14, and Maraba virus15. While the focus of the majority of these studies was on identifying host factors that influence some aspect of virus replication and not on identifying biotherapeutic targets for enhancing oncolytic virus therapy, valuable data could be mined from these data sets in this regard. It is clear that the powerful potential to identify host targets that can be manipulated to enhance oncolytic virus therapy has not been fully exploited.
A plethora of oncolytic virus platforms are currently being tested in preclinical and clinical studies including herpes simplex virus, reovirus and vaccinia virus, which have had demonstrable success in late-stage clinical trials. For the majority of these platforms, efforts have been directed toward altering the virus genomes to enhance therapy. For instance, to increase tumor specificity, specific virus genes have been deleted or mutated to significantly restrict viral replication in normal cells, but not in tumor cells. In some cases, transgenes have been added like GM-CSF (granulocyte macrophage colony-stimulating factor) to potentiate the immune response or NIS (sodium iodide symporter) to enable in vivo imaging and cellular radioiodide uptake for therapeutic purposes. However, there has been very little work focused on manipulating host/tumor genes and exploring the impact of host/tumor genes on oncolytic virus replication. With the advent of high-throughput screening technology, it is now possible to probe host-virus interactions on a genome scale and to decipher opportunities to manipulate the host genome to enhance oncolytic virus therapy (Reviewed in16,17,18).
We reported the first study demonstrating proof-of-concept for using high-throughput genetic screening to identify host targets that could be manipulated to enhance oncolytic virus therapy. To discover host genes that modulate Maraba virus oncolysis, an oncolytic rhabdovirus currently being tested in phase I and II trials, we conducted genome-wide RNAi screens across three different tumor cell lines in duplicate with an siRNA (short interfering RNA) library targeting 18,120 genes15. Pathway analysis of hits identified in the screens revealed enrichment of members of the ER (endoplasmic reticulum) stress response pathways. We selected 10 hits within these pathways for secondary validation using siRNA with different targeting sequences from those of the primary screen. As part of tertiary validation, we conducted a rescue experiment with IRE1&#945; (inositol-requiring enzyme 1 alpha) to confirm that the hit was on target. In vitro and in vivo testing using a small molecule inhibitor of IRE1&#945; resulted in dramatically enhanced oncolytic efficacy.
Workenhe et al.12 also conducted a genome-wide RNAi screen using a pooled lentiviral shRNA (short hairpin RNA) library targeting 16,056 genes to identify host factors restricting the human herpes simplex virus type 1 (HSV-1) mutant KM100-mediated oncolysis of breast cancer cells. In the primary screen, they identified 343 genes the knockdown of which lead to enhanced cytotoxicity of KM100-infected cells over mock-infected cells; they selected 24 of these genes for secondary validation. Out of the 24 genes, 8 genes were confirmed in the secondary screen with one of them being SRSF2 (serine/arginine-rich splicing factor 2) which was subsequently confirmed using a genetic rescue experiment during tertiary validation. The group went on to identify a DNA topoisomerase inhibitor chemotherapeutic that reduced the phosphorylation of SRSF2 and showed that the combination treatment of HSV-1 KM100 with this inhibitor lead to extended survival of TUBO tumor-bearing mice.
In the aforementioned studies, a similar workflow was followed. Each began with a primary genome-wide RNAi screen followed by a secondary screen on a select number of hits identified in the primary screen. This was followed by tertiary validation studies, which included confirming that the hit was on-target by performing genetic rescue experiments in vitro with ultimate validation performed by manipulating the target gene product in vivo. In this article, we first provide a general protocol for the development and validation of a high-throughput siRNA-screening assay, which involves determining the optimal transfection conditions, amount of virus, and length of infection. We also offer a detailed protocol for conducting a primary a high-throughput siRNA screen as well as an overall description of the method for performing secondary screen validation and tertiary validation.

<table>
	<tbody>
		<tr>
			<td>Consumables</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>siRNA library</td>
			<td>GE Dharmacon</td>
			<td>G-005005-02</td>
			<td></td>
		</tr>
		<tr>
			<td>Corning 384-well plate</td>
			<td>Corning</td>
			<td>3985</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon 384-well plate</td>
			<td>Becton Dickinson</td>
			<td>353962</td>
			<td></td>
		</tr>
		<tr>
			<td>Water</td>
			<td>Sigma</td>
			<td>W4502</td>
			<td></td>
		</tr>
		<tr>
			<td>siGenome SMARTpool PLK1</td>
			<td>GE Dharmacon</td>
			<td>M-003290-01</td>
			<td></td>
		</tr>
		<tr>
			<td>AllStars Negative Control siRNA</td>
			<td>Qiagen</td>
			<td>SI03650318</td>
			<td></td>
		</tr>
		<tr>
			<td>siGenome Non-targeting siRNA Pool #2</td>
			<td>GE Dharmacon</td>
			<td>D-001206-14-20</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM/HIGH Glucose</td>
			<td>GE Healthcare Life Sciences</td>
			<td>SH30022.01</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Sigma</td>
			<td>F15051-500ML</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES solution (1M)</td>
			<td>Sigma</td>
			<td>H3535-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin 100X solution</td>
			<td>GE Healthcare Life Sciences</td>
			<td>SV30010</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin-EDTA (0.25%)</td>
			<td>Thermo Fisher Scientific</td>
			<td>2500056</td>
			<td></td>
		</tr>
		<tr>
			<td>DPBS/Modified</td>
			<td>GE Healthcare Life Sciences</td>
			<td>SH30028.02</td>
			<td></td>
		</tr>
		<tr>
			<td>Lipofectamine RNAiMAX</td>
			<td>Thermo Fisher Scientific</td>
			<td>13778100</td>
			<td></td>
		</tr>
		<tr>
			<td>Oligofectamine</td>
			<td>Thermo Fisher Scientific</td>
			<td>1225011</td>
			<td></td>
		</tr>
		<tr>
			<td>Opti-MEM</td>
			<td>Thermo Fisher Scientific</td>
			<td>22600-050</td>
			<td></td>
		</tr>
		<tr>
			<td>Resazurin sodium salt</td>
			<td>Sigma</td>
			<td>R7017-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>Hoechst 33342</td>
			<td>Thermo Fisher Scientific</td>
			<td>H21492</td>
			<td></td>
		</tr>
		<tr>
			<td>Formaldehyde (37% by weight)</td>
			<td>Fisher Scientific</td>
			<td>F79-4</td>
			<td></td>
		</tr>
		<tr>
			<td>500 ml bottles</td>
			<td>Corning</td>
			<td>430282</td>
			<td></td>
		</tr>
		<tr>
			<td>Adhesive Sealing Film For Microplates</td>
			<td>Excel Scientific</td>
			<td>361006007</td>
			<td></td>
		</tr>
		<tr>
			<td>Peelable Heat Sealing Foil</td>
			<td>Thermo Fisher Scientific</td>
			<td>AB-3720</td>
			<td></td>
		</tr>
		<tr>
			<td>BioTek MicroFlo Select Dispenser cassette</td>
			<td>Fisher Scientific</td>
			<td>11-120-625</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MicroFlo Select (liquid dispenser)</td>
			<td>Fisher Scientific</td>
			<td>11120621</td>
			<td></td>
		</tr>
		<tr>
			<td>BioTek Synergy HT plate reader</td>
			<td>Biotek</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Opera Imaging and Analysis Instrument</td>
			<td>PerkinElmer</td>
			<td>HH10000115</td>
			<td></td>
		</tr>
		<tr>
			<td>KiNEDx Robotic Arm</td>
			<td>Peak Analysis and Automation (formerly Peak Robotics)</td>
			<td>KX-300-660</td>
			<td></td>
		</tr>
		<tr>
			<td>Cytomat 24C Series Automated Incubator</td>
			<td>Thermo Fisher Scientific</td>
			<td>50080227</td>
			<td></td>
		</tr>
		<tr>
			<td>JANUS Automated Workstation</td>
			<td>PerkinElmer</td>
			<td>AJI4M01</td>
			<td></td>
		</tr>
		<tr>
			<td>Plate Carousel</td>
			<td>Peak Analysis and Automation (formerly Peak Robotics)</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Alps 3000 plate sealer</td>
			<td>Thermo Fisher Scientific</td>
			<td>AB-3000</td>
			<td></td>
		</tr>
	</tbody>
</table>

genome-wide rnai screening to identify host factors that modulate oncolytic virus therapy

High-throughput genome-wide RNAi (RNA interference) screening technology has been widely used for discovering host factors that impact&#160;virus replication. Here we present the application of this technology to uncovering host targets that specifically modulate the replication of Maraba virus, an oncolytic rhabdovirus, and vaccinia virus with the goal of enhancing therapy. While the protocol has been tested for use with oncolytic Maraba virus and oncolytic vaccinia virus, this approach is applicable to other oncolytic viruses and can also be utilized for identifying host targets that modulate virus replication in mammalian cells in general. This protocol describes the development and validation of an assay for high-throughput RNAi screening in mammalian cells, the key considerations and preparation steps important for conducting a primary high-throughput RNAi screen, and a step-by-step guide for conducting a primary high-throughput RNAi screen; in addition, it broadly outlines the methods for conducting secondary screen validation and tertiary validation studies. The benefit of high-throughput RNAi screening is that it allows one to catalogue, in an extensive and unbiased fashion, host factors that modulate any aspect of virus replication for which one can develop an in vitro assay such as infectivity, burst size, and cytotoxicity. It has the power to uncover biotherapeutic targets unforeseen based on current knowledge.

An overview of the workflow for identifying host targets to enhance oncolytic virus therapy is presented in Figure 1.
As illustrated in Figure 1, the critical first step to conducting a high-throughput RNAi screen is assay development. Figure 2A provides a sample plate layout for the transfection optimization assay. Fig...

Watch this Scientific Journal Video about Genome-wide RNAi Screening to Identify Host Factors That Modulate Oncolytic Virus Therapy at JoVE.com

Genome-wide RNAi Screening to Identify Host Factors That Modulate Oncolytic Virus Therapy

Here we describe a protocol for employing high-throughput RNAi screening to uncover host targets that can be manipulated to enhance oncolytic virus therapy, specifically rhabodvirus and vaccinia virus therapy, but it can be readily adapted to other oncolytic virus platforms or for discovering host genes that modulate virus replication generally.

High-throughput genome-wide RNAi (RNA interference) screening technology has been widely used for discovering host factors that impact&#160;virus ...

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