This study was partly funded by the Mayo Clinic Center for Individualized Medicine (SSK), Mayo Clinic Comprehensive&#160;Cancer Center (SSK), Mayo Clinic Center for Regenerative Biotherapeutics (SSK), National Institutes of Health K12CA090628 (SSK) and R37CA266344-01 (SSK), Department of Defense grant CA201127 (SSK), Predolin Foundation (SSK), and Minnesota Partnership for Biotechnology and Medical Genomics (SSK). CMS is supported by the Mayo Clinic Graduate School of Biomedical Sciences. CRISPR screen schematic (Figure 1) was created with BioRender.com (Siegler, L. (2022) https://BioRender.com/k71r054).&#160;

Genome-Wide CRISPR Screens in CART Cells to Investigate Therapy Resistance

<ol><li>Neelapu, S. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((5-year+follow-up+supports+curative+potential+of+axicabtagene+ciloleucel+in+refractory+large+B-cell+lymphoma+%28zuma-1%29%5BTitle%5D)+AND+%22Blood%22%5BJournal%5D)">5-year follow-up supports curative potential of axicabtagene ciloleucel in refractory large B-cell lymphoma (zuma-1).</a> Blood. 141 (19), 2307-2315 (2023).</li>
<li>Neelapu, S. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Axicabtagene+ciloleucel+CAR+T-cell+therapy+in+refractory+large+B-cell+lymphoma%5BTitle%5D)+AND+%22N+Engl+J+Med%22%5BJournal%5D)">Axicabtagene ciloleucel CAR T-cell therapy in refractory large B-cell lymphoma.</a> N Engl J Med. 377 (26), 2531-2544 (2017).</li>
<li>Locke, F. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Long-term+safety+and+activity+of+axicabtagene+ciloleucel+in+refractory+large+B-cell+lymphoma+%28zuma-1%29%3A+A+single-arm%2C+multicentre%2C+phase+1-2+trial%5BTitle%5D)+AND+%22Lancet+Oncol%22%5BJournal%5D)">Long-term safety and activity of axicabtagene ciloleucel in refractory large B-cell lymphoma (zuma-1): A single-arm, multicentre, phase 1-2 trial.</a> Lancet Oncol. 20 (1), 31-42 (2019).</li>
<li>Maude, S. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tisagenlecleucel+in+children+and+young+adults+with+B-cell+lymphoblastic+leukemia%5BTitle%5D)+AND+%22N+Engl+J+Med%22%5BJournal%5D)">Tisagenlecleucel in children and young adults with B-cell lymphoblastic leukemia.</a> N Engl J Med. 378 (5), 439-448 (2018).</li>
<li>Schuster, S. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tisagenlecleucel+in+adult+relapsed+or+refractory+diffuse+large+B-cell+lymphoma%5BTitle%5D)+AND+%22N+Engl+J+Med%22%5BJournal%5D)">Tisagenlecleucel in adult relapsed or refractory diffuse large B-cell lymphoma.</a> N Engl J Med. 380 (1), 45-56 (2018).</li>
<li>Bai, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Single-cell+antigen-specific+landscape+of+CAR+T+infusion+product+identifies+determinants+of+CD19-positive+relapse+in+patients+with+all%5BTitle%5D)+AND+%22Sci+Adv%22%5BJournal%5D)">Single-cell antigen-specific landscape of CAR T infusion product identifies determinants of CD19-positive relapse in patients with all.</a> Sci Adv. 8 (23), eabj2820(2022).</li>
<li>Fraietta, J. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Determinants+of+response+and+resistance+to+CD19+chimeric+antigen+receptor+%28CAR%29+T+cell+therapy+of+chronic+lymphocytic+leukemia%5BTitle%5D)+AND+%22Nat+Med%22%5BJournal%5D)">Determinants of response and resistance to CD19 chimeric antigen receptor (CAR) T cell therapy of chronic lymphocytic leukemia.</a> Nat Med. 24, 563-571 (2018).</li>
<li>Gennert, D. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Dynamic+chromatin+regulatory+landscape+of+human+CAR+T+cell+exhaustion%5BTitle%5D)+AND+%22Proc+Natl+Acad+Sci+USA%22%5BJournal%5D)">Dynamic chromatin regulatory landscape of human CAR T cell exhaustion.</a> Proc Natl Acad Sci USA. 118 (30), e2104758118(2021).</li>
<li>Deng, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Characteristics+of+anti-CD19+CAR+T+cell+infusion+products+associated+with+efficacy+and+toxicity+in+patients+with+large+B+cell+lymphomas%5BTitle%5D)+AND+%22Nat+Med%22%5BJournal%5D)">Characteristics of anti-CD19 CAR T cell infusion products associated with efficacy and toxicity in patients with large B cell lymphomas.</a> Nat Med. 26 (12), 1878-1887 (2020).</li>
<li>Sterner, R. M., Cox, M. J., Sakemura, R., Kenderian, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Using+CRISPR%2FCAS9+to+knock+out+GM-CSF+in+CAR-T+cells%5BTitle%5D)+AND+%22J+Vis+Exp%22%5BJournal%5D)">Using CRISPR/CAS9 to knock out GM-CSF in CAR-T cells.</a> J Vis Exp. (149), e59629(2019).</li>
<li>Sterner, R. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((GM-CSF+inhibition+reduces+cytokine+release+syndrome+and+neuroinflammation+but+enhances+CAR-T+cell+function+in+xenografts%5BTitle%5D)+AND+%22Blood%22%5BJournal%5D)">GM-CSF inhibition reduces cytokine release syndrome and neuroinflammation but enhances CAR-T cell function in xenografts.</a> Blood. 133 (7), 697-709 (2019).</li>
<li>Cox, M. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((GM-CSF+disruption+in+CART+cells+modulates+T+cell+activation+and+enhances+CART+cell+anti-tumor+activity%5BTitle%5D)+AND+%22Leukemia%22%5BJournal%5D)">GM-CSF disruption in CART cells modulates T cell activation and enhances CART cell anti-tumor activity.</a> Leukemia. 36 (6), 1635-1645 (2022).</li>
<li>Ottaviano, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Phase+1+clinical+trial+of+CRISPR-engineered+CAR19+universal+T+cells+for+treatment+of+children+with+refractory+B+cell+leukemia%5BTitle%5D)+AND+%22Sci+Transl+Med%22%5BJournal%5D)">Phase 1 clinical trial of CRISPR-engineered CAR19 universal T cells for treatment of children with refractory B cell leukemia.</a> Sci Transl Med. 14 (668), eabq3010(2022).</li>
<li>Joung, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Genome-scale+CRISPR-CAS9+knockout+and+transcriptional+activation+screening%5BTitle%5D)+AND+%22Nat+Protoc%22%5BJournal%5D)">Genome-scale CRISPR-CAS9 knockout and transcriptional activation screening.</a> Nat Protoc. 12, 828-863 (2017).</li>
<li>Mccutcheon, S. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Transcriptional+and+epigenetic+regulators+of+human+CD8%2B+T+cell+function+identified+through+orthogonal+CRISPR+screens%5BTitle%5D)+AND+%22Nat+Genet%22%5BJournal%5D)">Transcriptional and epigenetic regulators of human CD8+ T cell function identified through orthogonal CRISPR screens.</a> Nat Genet. 55, 2211-2223 (2023).</li>
<li>Zhu, W., Kelly, C., Dagur, P., Dunbar, C. E., Cordes, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((CRISPR+activation+screen+to+optimize+chimeric+antigen+receptor+%28CAR%29+T+cell+immunophenotype%5BTitle%5D)+AND+%22Blood%22%5BJournal%5D)">CRISPR activation screen to optimize chimeric antigen receptor (CAR) T cell immunophenotype.</a> Blood. 142 (Supplement 1), 4820-4820 (2023).</li>
<li>Wang, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((CRISPR+screening+of+CAR+T+cells+and+cancer+stem+cells+reveals+critical+dependencies+for+cell-based+therapies%5BTitle%5D)+AND+%22Cancer+Discov%22%5BJournal%5D)">CRISPR screening of CAR T cells and cancer stem cells reveals critical dependencies for cell-based therapies.</a> Cancer Discov. 11 (5), 1192-1211 (2021).</li>
<li>Shifrut, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Genome-wide+CRISPR+screens+in+primary+human+T+cells+reveal+key+regulators+of+immune+function%5BTitle%5D)+AND+%22Cell%22%5BJournal%5D)">Genome-wide CRISPR screens in primary human T cells reveal key regulators of immune function.</a> Cell. 175 (7), 1958-1971.e15 (2018).</li>
<li>Belk, J. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Genome-wide+crispr+screens+of+T+cell+exhaustion+identify+chromatin+remodeling+factors+that+limit+T+cell+persistence%5BTitle%5D)+AND+%22Cancer+Cell%22%5BJournal%5D)">Genome-wide crispr screens of T cell exhaustion identify chromatin remodeling factors that limit T cell persistence.</a> Cancer Cell. 40 (7), 768-786.e7 (2022).</li>
<li>Jiang, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Single-cell+ATAC-seq+maps+the+comprehensive+and+dynamic+chromatin+accessibility+landscape+of+CAR-T+cell+dysfunction%5BTitle%5D)+AND+%22Leukemia%22%5BJournal%5D)">Single-cell ATAC-seq maps the comprehensive and dynamic chromatin accessibility landscape of CAR-T cell dysfunction.</a> Leukemia. 36 (11), 2656-2668 (2022).</li>
<li>Rossi, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Preinfusion+polyfunctional+anti-CD19+chimeric+antigen+receptor+T+cells+are+associated+with+clinical+outcomes+in+NHL%5BTitle%5D)+AND+%22Blood%22%5BJournal%5D)">Preinfusion polyfunctional anti-CD19 chimeric antigen receptor T cells are associated with clinical outcomes in NHL.</a> Blood. 132 (8), 804-814 (2018).</li>
<li>Beider, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Molecular+and+functional+signatures+associated+with+CAR+T+cell+exhaustion+and+impaired+clinical+response+in+patients+with+B+cell+malignancies%5BTitle%5D)+AND+%22Cells%22%5BJournal%5D)">Molecular and functional signatures associated with CAR T cell exhaustion and impaired clinical response in patients with B cell malignancies.</a> Cells. 11 (7), 1140(2022).</li>
<li>Wherry, E. J. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((cell+exhaustion%5BTitle%5D)+AND+%22Nat+Immunol%22%5BJournal%5D)">cell exhaustion.</a> Nat Immunol. 12, 492-499 (2011).</li>
<li>Prinzing, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Deleting+DNMT3A+in+CAR+T+cells+prevents+exhaustion+and+enhances+antitumor+activity%5BTitle%5D)+AND+%22Sci+Transl+Med%22%5BJournal%5D)">Deleting DNMT3A in CAR T cells prevents exhaustion and enhances antitumor activity.</a> Sci Transl Med. 13, eabh0272(2021).</li>
<li>Lynn, R. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((C-jun+overexpression+in+CAR+T+cells+induces+exhaustion+resistance%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">C-jun overexpression in CAR T cells induces exhaustion resistance.</a> Nature. 576, 293-300 (2019).</li>
<li>Tang, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((TGF-beta+inhibition+via+CRISPR+promotes+the+long-term+efficacy+of+CAR+T+cells+against+solid+tumors%5BTitle%5D)+AND+%22JCI+Insight%22%5BJournal%5D)">TGF-beta inhibition via CRISPR promotes the long-term efficacy of CAR T cells against solid tumors.</a> JCI Insight. 5 (4), e133977(2020).</li>
<li>Joung, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Genome-scale+CRISPR-CAS9+knockout+and+transcriptional+activation+screening%5BTitle%5D)+AND+%22Nat+Protoc%22%5BJournal%5D)">Genome-scale CRISPR-CAS9 knockout and transcriptional activation screening.</a> Nat Protoc. 12 (4), 828-863 (2017).</li>
<li>Li, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Quality+control%2C+modeling%2C+and+visualization+of+CRISPR+screens+with+MAGeCK-VISPR%5BTitle%5D)+AND+%22Genome+Biol%22%5BJournal%5D)">Quality control, modeling, and visualization of CRISPR screens with MAGeCK-VISPR.</a> Genome Biol. 16, 281(2015).</li>
<li>Sakemura, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Targeting+cancer-associated+fibroblasts+in+the+bone+marrow+prevents+resistance+to+CART-cell+therapy+in+multiple+myeloma%5BTitle%5D)+AND+%22Blood%22%5BJournal%5D)">Targeting cancer-associated fibroblasts in the bone marrow prevents resistance to CART-cell therapy in multiple myeloma.</a> Blood. 139 (26), 3708-3721 (2022).</li>
<li>Stewart, C. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((IL-4+drives+exhaustion+of+CD8%2B+CART+cells%5BTitle%5D)+AND+%22Nat+Commun%22%5BJournal%5D)">IL-4 drives exhaustion of CD8+ CART cells.</a> Nat Commun. 15 (1), 7921(2024).</li>
<li>FastQC: A quality control tool for high throughput sequence data. , Babraham Bioinformatics. 
 <a target="_blank" href=" https://www.bioinformatics.babraham.ac.uk/projects/fastqc/"> https://www.bioinformatics.babraham.ac.uk/projects/fastqc/</a> (2010).</li>
<li>Bbmerge. , 
 <a target="_blank" href=" https://github.com/BioInfoTools/BBMap/blob/master/sh/bbmerge.sh"> https://github.com/BioInfoTools/BBMap/blob/master/sh/bbmerge.sh</a> (2019).</li>
<li>Pattanayak, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((High-throughput+profiling+of+off-target+DNA+cleavage+reveals+RNA-programmed+CAS9+nuclease+specificity%5BTitle%5D)+AND+%22Nat+Biotechnol%22%5BJournal%5D)">High-throughput profiling of off-target DNA cleavage reveals RNA-programmed CAS9 nuclease specificity.</a> Nat Biotechnol. 31 (9), 839-843 (2013).</li>
<li>Doench, J. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Rational+design+of+highly+active+sgRNAs+for+CRISPR-CAS9-mediated+gene+inactivation%5BTitle%5D)+AND+%22Nat+Biotechnol%22%5BJournal%5D)">Rational design of highly active sgRNAs for CRISPR-CAS9-mediated gene inactivation.</a> Nat Biotechnol. 32 (12), 1262-1267 (2014).</li>
<li>Dong, M. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Systematic+immunotherapy+target+discovery+using+genome-scale+in+vivo+CRISPR+screens+in+CD8+T+cells%5BTitle%5D)+AND+%22Cell%22%5BJournal%5D)">Systematic immunotherapy target discovery using genome-scale in vivo CRISPR screens in CD8 T cells.</a> Cell. 178 (5), 1189-1204.e23 (2019).</li>
<li>Zhou, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Single-cell+CRISPR+screens+in+vivo+map+T+cell+fate+regulomes+in+cancer%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">Single-cell CRISPR screens in vivo map T cell fate regulomes in cancer.</a> Nature. 624 (7990), 154-163 (2023).</li>
<li>Sutra Del Galy, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((In+vivo+genome-wide+CRISPR+screens+identify+SOCS1+as+intrinsic+checkpoint+of+CD4%2B+TH1+cell+response%5BTitle%5D)+AND+%22Sci+Immunol%22%5BJournal%5D)">In vivo genome-wide CRISPR screens identify SOCS1 as intrinsic checkpoint of CD4+ TH1 cell response.</a> Sci Immunol. 6 (66), eabe8219(2021).</li>
<li>Ramos, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Leukemia-intrinsic+determinants+of+CAR-T+response+revealed+by+iterative+in+vivo+genome-wide+CRISPR+screening%5BTitle%5D)+AND+%22Nat+Commun%22%5BJournal%5D)">Leukemia-intrinsic determinants of CAR-T response revealed by iterative in vivo genome-wide CRISPR screening.</a> Nat Commun. 14 (1), 8048(2023).</li>
</ol>

SSK is an inventor on patents in the field of CAR immunotherapy that are licensed to Novartis (through an agreement between Mayo Clinic, University of Pennsylvania, and Novartis), Humanigen (through Mayo Clinic), Mettaforge (through Mayo Clinic), and MustangBio (through Mayo Clinic), and Chymal therapeutics (through Mayo Clinic). CS, CMR, and SSK are inventors on patents that are licensed to Immix Biopharma. SSK receives research funding from Kite, Gilead, Juno, BMS, Novartis, Humanigen, MorphoSys, Tolero, Sunesis/Viracta, LifEngine Animal Health Laboratories Inc., and Lentigen. SSK has participated in advisory meetings with Kite/Gilead, Calibr, Luminary Therapeutics, Humanigen, Juno/BMS, Capstan Bio, and Novartis. SSK has served on the data safety and monitoring board with Humanigen and Carisma. SSK has severed a consultant for Torque, Calibr, Novartis, Capstan Bio, BMS, Carisma, and Humanigen. CMS and SSK are inventors of intellectual property that resulted from this protocol.

Gene editing has become a powerful tool in both understanding the mechanisms of resistance to therapies as well as designing novel CART cell therapies to improve the longevity and activity of CART cells16,17,26. While some gene editing strategies have shown improvements in CART cell activity in both preclinical models and clinical trials, there is still work to be done to optimize gene editing strategies. To address this need, r...

Chimeric antigen receptor T (CART) cell therapy has shown impressive success in the treatment of B-cell malignancies; however, the durable response is limited to 30-40%1,2,3,4,5. While researchers have developed and tested several approaches to address mechanisms of resistance to CART cell therapy, including the optimization of CAR design, gene editing, and combination therapies, the development of resistance remains largely unknown. Recently, there has been increasing evidence that the baseline gene expression profile of preinfusion CART cell products is an important determinant of both the toxicity and efficacy of CART therapy6,7,8,9. As such, gene editing during CART cell production has become a popular approach to improve CART cell therapy success.
For instance, our lab previously showed that using clustered regularly interspaced short palindromic repeats (CRISPR) Cas9 technology to knock out the gene granulocyte-macrophage colony-stimulating factor (GM-CSF) improves CART cell activity and reduces signs of CART-associated toxicity10,11,12. Additionally, CRISPR-engineered cell therapy has been tested in clinical trials and has shown efficacy and safety13. Together, this indicates that gene editing with CRISPR technology can not only enhance our understanding of CART cell biology but also generate translatable CART cell products.
Genome-wide CRISPR knockout screens have become increasingly popular tools in cancer biology research to understand mechanisms of resistance to therapeutics. In this technique, tens of thousands of guide RNAs (gRNAs) are delivered to pools of cells to encourage the entry of one gRNA per cell14. Then, cells undergo pressure-inducing conditions where cells transduced with gRNAs targeting essential genes die and cells transduced with gRNAs targeting inhibitory genes survive and proliferate. By using next-generation sequencing, we can determine how gRNA representation changes throughout the CRISPR screen14.
However, the scale and selection time required for genome-wide gene perturbations can be challenging to accomplish in primary cells, like CART cells. As such, groups have utilized targeted CRISPR screens to further understand the mechanisms of therapeutic resistance15,16. Targeted screens are often easier to complete in primary cells because they have smaller libraries that require fewer cells to achieve adequate library representation. While these studies have improved our understanding of mechanisms of resistance to CART cell therapy, targeted screens introduce a bias due to the manual selection of gene targets. This article seeks to describe a method to complete an in vitro genome-wide CRISPR knockout screen in CART cells from healthy donors. As such, this high-throughput approach allows for efficient, unbiased identification of key pathways and genes that can be edited to improve therapeutic responses17,18,19.
In particular, the protocol described in this article is designed to increase the field&#39;s understanding of CART cell exhaustion by completing the genome-wide CRISPR knockout screen with an in vitro model for exhaustion. Exhaustion is a dysfunctional CART cell fate that has been implicated in non-response to CART cell therapy20,21,22. This cellular fate is known to be epigenetically regulated, and it is characterized by a decrease in CART cell proliferation, a decrease in effector cytokine production, and an increase in the expression of inhibitory receptors23. In prior literature, gene editing has been able to prevent the development of exhaustion by either up- or downregulating key genes24,25,26. Given both the decrease in proliferative ability as CART cells become exhausted and the evidence that gene editing can prevent its occurrence, we modeled our in vitro genome-wide CRISPR knockout screen on this cellular fate. However, this protocol could be amended in the future to explore other mechanisms of resistance to CART cell therapy.

<table><tbody><tr><td>293T cells</td><td>ATCC</td><td>CRL-3216</td><td>Cells used for lentivirus production</td></tr><tr><td>Biotin ProteinL Antibody</td><td>GenScript</td><td>M00097</td><td>anti-kappa chain antibody for CAR detection</td></tr><tr><td>Bovine Serum Albumin</td><td>Millipore Sigma</td><td>A7906</td><td></td></tr><tr><td>Carbenicillin disodium salt</td><td>Millipore Sigma</td><td>C1389-1G</td><td>Carbenicillin antibiotic</td></tr><tr><td>CD4 Isolation Beads</td><td>Miltenyi Biotec</td><td>130-045-101&amp;nbsp;</td><td></td></tr><tr><td>CD8 Isolation Beads</td><td>Miltenyi Biotec</td><td>130-045-201</td><td></td></tr><tr><td>CTS (Cell Therapy Systems) Dynabeads CD3/CD28</td><td>Gibco</td><td>40203D</td><td></td></tr><tr><td>Cytoflex</td><td>Beckman Coulter</td><td>NC2279958</td><td></td></tr><tr><td>DNase-Free Water</td><td>Invitrogen</td><td>AM9937</td><td></td></tr><tr><td>Dulbecco&#039;s modified eagle&#039;s medium (DMEM)</td><td>Corning</td><td>10-017-CV</td><td></td></tr><tr><td>Dulbecco&#039;s Phosphate-Buffered Saline</td><td>Gibco</td><td>14190-144</td><td></td></tr><tr><td>EasySep Human T Cell Isolation Kit</td><td>STEMCELL Technologies</td><td>17951RF</td><td>Negative isolation kit</td></tr><tr><td>Endura Electrocompetent Cells&amp;nbsp;</td><td>Biosearch Technologies</td><td>60242-1</td><td>Electrocompetent cells with recovery medium</td></tr><tr><td>Ethanol</td><td>Millipore Sigma</td><td>E7023</td><td></td></tr><tr><td>Fetal bovine serum (FBS)</td><td>Corning</td><td>35-010-CV</td><td></td></tr><tr><td>GeCKO v2 CRISPR Knockout Pooled Library A</td><td>AddGene</td><td>1000000048</td><td>CRISPR library plasmid</td></tr><tr><td>Gene Pulser II&amp;nbsp;</td><td>Bio-Rad</td><td>165-2105</td><td>Electroporator</td></tr><tr><td>Glycogen</td><td>Millipore Sigma</td><td>10901393001</td><td></td></tr><tr><td>JeKo-1</td><td>ATCC</td><td>CRL-3006</td><td>CD19&lt;sup&gt;+&lt;/sup&gt; target cells&amp;nbsp;</td></tr><tr><td>Lipofectamine 3000 Transfection Reagent</td><td>ThermoFisher Scientific</td><td>L3000075</td><td>Transfection reagent kit with a transfection reagent (Lipofectamine 3000 Reagent) and a neutral co-lipid reagent (p3000)</td></tr><tr><td>LIVE/DEAD Aqua</td><td>Invitrogen</td><td>L34966</td><td></td></tr><tr><td>Lymphoprep</td><td>STEMCELL Technologies</td><td>7851</td><td>Density gradient medium</td></tr><tr><td>Machery-Nagel NucleoBond Xtra Maxi Kits</td><td>ThermoFisher Scientific</td><td>12748412</td><td>Maxi-prep kit</td></tr><tr><td>NEBNext High-Fidelity 2X PCR MasterMix</td><td>New England BioLabs</td><td>M0541S</td><td>High fidelity PCR mastermix</td></tr><tr><td>Opti-MEM I Reduced Serum Medium</td><td>Gibco</td><td>31985-070</td><td>Reduced serum medium</td></tr><tr><td>pCMVR8.74</td><td>AddGene</td><td>22036</td><td>Lentiviral packaging plasmid</td></tr><tr><td>Pennicillin-streptomycin-glutamine (100X)</td><td>Life Technologies</td><td>10378-016</td><td></td></tr><tr><td>pMD2.G</td><td>AddGene</td><td>12259</td><td>VSV-G envelope expressing plasmid</td></tr><tr><td>Pooled Human AB Serum&amp;nbsp;</td><td>Innovative Research</td><td>ISERABHI</td><td></td></tr><tr><td>Puromycin</td><td>Millipore Sigma</td><td>P8833</td><td></td></tr><tr><td>QIAquick Gel Extraction Kit</td><td>Qiagen</td><td>28704</td><td>Gek extraction kit</td></tr><tr><td>Qucik-DNA Midiprep Plus Kit</td><td>Zymo Research</td><td>D4075</td><td>Kit used to isolate gDNA</td></tr><tr><td>RoboSep-S</td><td>STEMCELL Technologies</td><td>21000</td><td>Automated cell separator</td></tr><tr><td>Roswell Park Memorial Institute 1640 Medium (RPMI)</td><td>Gibco</td><td>21870092</td><td></td></tr><tr><td>SepMate-50</td><td>STEMCELL Technologies</td><td>85450</td><td>Density gradient separation tube</td></tr><tr><td>Sodium Acetate</td><td>Invitrogen</td><td>AM9740</td><td></td></tr><tr><td>Sodium Azide</td><td>Fisher Scientific</td><td>71448-16</td><td></td></tr><tr><td>Streptavidin Antibody (PE)</td><td>BioLegend</td><td>405203</td><td>Secondary antibody used for CAR detection</td></tr><tr><td>T100 Thermal Cycler</td><td>Bio-Rad</td><td>1861096</td><td></td></tr><tr><td>Ultracentrifuge (Optima XPN-80)</td><td>BeckmanCoulter</td><td>A99839</td><td></td></tr><tr><td>Vacuum Filter Systems, 0.22 &amp;micro;m</td><td>ThermoFisher Scientific</td><td>567-0020</td><td></td></tr><tr><td>Vacuum Filter Systems, 0.45 &amp;micro;m</td><td>ThermoFisher Scientific</td><td>165-0045</td><td></td></tr><tr><td>X-VIVO 15 Serum-Free Hematopoietic Cell Medium</td><td>Lonza</td><td>04-418Q</td><td>Hematopoietic cell medium</td></tr></tbody></table>

performing an in vitro genome-wide crispr knockout screen in chimeric antigen receptor t cells

Chimeric antigen receptor T (CART) cell therapy is an innovative form of targeted immunotherapy that has revolutionized the treatment of cancer. However, the durable response remains limited. Recent studies have shown that the epigenetic landscape of preinfusion CART cell products can influence response to therapy, and gene editing has been proposed as a solution. However, more work needs to be done to determine the optimal gene editing strategy. Genome-wide CRISPR screens have become popular tools to both investigate mechanisms of resistance and optimize gene editing strategies. Yet their application to primary cells presents many challenges. Here we describe a method to complete a genome-wide CRISPR knockout screen in CART cells from healthy donors. As a proof-of-concept model, we designed this method to investigate the development of exhaustion in CART cells targeting the CD19 antigen. However, we believe that this approach can be used to address a variety of mechanisms of resistance to therapy in different CAR constructs and tumor models.

To interrogate genes and pathways that can be edited to improve CART cell activity in an unbiased manner, we designed an in vitro genome-wide CRISPR knockout screen (Figure 1). This screen has two phases: a CART cell production phase and a selective pressure phase. In the CART cell production phase, at least 110 &#215; 106 T-cells are first isolated from healthy donor PBMCs and activated with CD3+/CD28+ beads. The following day, on Day 1</str...

Performing an In Vitro Genome-Wide CRISPR Knockout Screen in Chimeric Antigen Receptor T Cells

The article describes a protocol for the application of an in vitro model for exhaustion to complete a genome-wide CRISPR knockout screen in healthy donor chimeric antigen receptor T cells.

Chimeric antigen receptor T (CART) cell therapy is an innovative form of targeted immunotherapy that has revolutionized the treatment of cancer. However, ...

performing-an-vitro-genome-wide-crispr-knockout-screen-chimeric

Research

JoVE Journal

Cancer Research

794 Views.  Mayo Clinic. Het artikel beschrijft een protocol voor de toepassing van een in vitro model voor uitputting om een genoombrede CRISPR-knockoutscreening te voltooien in gezonde chimere antigeenreceptor-T-cellen van de donor. 

Video: Uitvoeren van een in vitro genoombrede CRISPR-knock-outscreening in chimere antigeenreceptor-T-cellen

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.

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 ...

In Vitro Tumor Cell Rechallenge For Predictive Evaluation of Chimeric Antigen Receptor T Cell Antitumor Function

The field of chimeric antigen receptor (CAR) T cell therapy is rapidly advancing with improvements in CAR design, gene-engineering approaches and manufacturing optimizations. One challenge for these development efforts, however, has been the establishment of in vitro assays that can robustly inform selection of the optimal CAR T cell products for in vivo therapeutic success. Standard in vitro tumor-lysis assays often fail to reflect the true antitumor potential of the CAR T cells due to the relatively short co-culture time and high T cell to tumor ratio. Here, we describe an in vitro co-culture method to evaluate CAR T cell recursive killing potential at high tumor cell loads. In this assay, long-term cytotoxic function and proliferative capacity of CAR T cells is examined in vitro over 7 days with additional tumor targets administered to the co-culture every other day. This assay can be coupled with profiling T cell activation, exhaustion and memory phenotypes. Using this assay, we have successfully distinguished the functional and phenotypic differences between CD4+ and CD8+ CAR T cells against glioblastoma (GBM) cells, reflecting their differential in vivo antitumor activity in orthotopic xenograft models. This method provides a facile approach to assess CAR T cell potency and to elucidate the functional variations across different CAR T cell products.

Here, we describe an in vitro co-culture method to recursively challenge tumor-targeted T cells, which allows for phenotypic and functional analysis of antitumor T cell activity.

The field of chimeric antigen receptor (CAR) T cell therapy is rapidly advancing with improvements in CAR design, gene-engineering approaches and ...

Evaluating Quantitative Tumor Cell Killing by CAR-Expressing Jurkat Cells

Rapid In Vitro Cytotoxicity Evaluation of Jurkat Expressing Chimeric Antigen Receptor using Fluorescent Imaging

Chimeric antigen receptor (CAR) T cells are at the forefront of oncology. A CAR is constructed of a targeting domain (usually a single chain variable fragment, scFv), with an accompanying intra-chain linker, followed by a hinge, transmembrane, and costimulatory domain. Modification of the intra-chain linker and hinge domain can have a significant effect on CAR-mediated killing. Considering the many different options for each part of a CAR construct, there are large numbers of permutations. Making CAR-T cells is a time-consuming and expensive process, and making and testing many constructs is a heavy time and material investment. This protocol describes a platform to rapidly evaluate hinge-optimized CAR constructs in Jurkat cells (CAR-J). Jurkat cells are an immortalized T cell line with high lentivirus uptake, allowing for efficient CAR transduction. Here, we present a platform to rapidly evaluate CAR-J using a fluorescent imager, followed by confirmation of cytolysis in PBMC-derived T cells.

Author Spotlight: High-Throughput Screening of CAR T-Cell Constructs for Enhanced Cytotoxicity and Immunologic Memory 

A protocol to evaluate quantitative tumor cell killing by Jurkat cells expressing chimeric antigen receptor (CAR) targeting single tumor antigen. This protocol can be used as a screening platform for rapid optimization of CAR hinge constructs prior to confirmation in peripheral blood-derived T cells.

Chimeric antigen receptor (CAR) T cells are at the forefront of oncology. A CAR is constructed of a targeting domain (usually a single chain variable ...

Streamlined Single Cell TCR Isolation and Generation of Retroviral Vectors for In Vitro and In Vivo Expression of Human TCRs

Although, several methods for sequencing of paired T cell receptor (TCR) alpha and beta chains from single T cells have been developed, none so far have been conducive to downstream in vivo functional analysis of TCR heterodimers. We have developed an improved protocol based on a two-step multiplex-nested PCR, which results in a PCR product that spans entire variable regions of a human TCR alpha and beta chains. By identifying unique restriction sites and incorporating them into the PCR primers, we have made the PCR product compatible with direct sub-cloning into the template retroviral vector. The resulting retroviral construct encodes a chimeric human/mouse TCR with a mouse intracellular domain, which is functional in mouse cells or in in vivo mouse models. Overall, the protocol described here combines human single cell paired TCR alpha and beta chain identification with streamlined generation of retroviral vectors readily adaptable for in vitro and in vivo TCR expression. The video and the accompanying material are designed to give a highly detailed description of the single cell PCR, so that the critical steps can be followed and potential pitfalls avoided. Additionally, we provide a detailed description of the cloning steps necessary to generate the expression vector. Once mastered, the whole procedure from single cell sorting to TCR expression could be performed in a short two-week period.

Streamlined Single Cell TCR Isolation and Generation of Retroviral Vectors for In Vitro and In Vivo Expression of Human TCRs

The current protocol combines single cell paired human TCR alpha and beta chain sequencing with streamlined generation of retroviral vectors compatible with in vitro and in vivo TCR expression.

Although, several methods for sequencing of paired T cell receptor (TCR) alpha and beta chains from single T cells have been developed, none so far have ...

Immunology and Infection

A Real-time Potency Assay for Chimeric Antigen Receptor T Cells Targeting Solid and Hematological Cancer Cells

Chimeric antigen receptor (CAR) T-cell therapy for cancer has achieved significant clinical benefit for resistant and refractory hematological malignancies such as childhood acute lymphocytic leukemia. Efforts are currently underway to extend this promising therapy to solid tumors in addition to other hematological cancers. Here, we describe the development and production of potent CAR T cells targeting antigens with unique or preferential expression on solid and liquid tumor cells. The in vitro potency of these CAR T cells is then evaluated in real-time using the highly sensitive impedance-based xCELLigence assay. Specifically, the impact of different costimulatory signaling domains, such as glucocorticoid-induced tumor necrosis factor receptor (TNFR)-related protein (GITR), on the in vitro potency of CAR T cells is examined. This report includes protocols for: generating CAR T cells for preclinical studies using lentiviral gene transduction, expanding CAR T cells, validating CAR expression, and running and analyzing xCELLigence potency assays.

We describe a quantitative real-time in vitro cytolysis assay system to evaluate the potency of chimeric antigen receptor T cells targeting liquid and solid tumor cells. This protocol can be extended to assess other immune effector cells, as well as combination treatments.

Chimeric antigen receptor (CAR) T-cell therapy for cancer has achieved significant clinical benefit for resistant and refractory hematological ...

Streamlined Protocol for Mouse CAR-T Cell Generation in Syngeneic Models

Efficient Generation of Murine Chimeric Antigen Receptor (CAR)-T Cells

Engineered cell therapies utilizing chimeric antigen receptor (CAR)-T cells have achieved remarkable effectiveness in individuals with hematological malignancies and are presently undergoing development for the treatment of diverse solid tumors. So far, the preliminary evaluation of novel CAR-T cell products has predominantly taken place in xenograft tumor models using immunodeficient mice. This approach is chosen to facilitate the successful engraftment of human CAR-T cells in the experimental setting. However, syngeneic mouse models, in which tumors and CAR-T cells are derived from the same mouse strain, allow evaluation of new CAR technologies in the context of a functional immune system and comprehensive tumor microenvironment (TME). The protocol described here aims to streamline the process of mouse CAR-T cell generation by presenting standardized methods for retroviral transduction and ex vivo T cell culture. The methods described in this protocol can be applied to other CAR constructs beyond the ones used in this study to enable routine evaluation of new CAR technologies in immune-competent systems.

Author Spotlight: Enhancing CAR-T Cell Function in Syngeneic Tumor Models 

This protocol streamlines retroviral vector production and murine T cell transduction, facilitating the efficient generation of mouse CAR-T cells.

Engineered cell therapies utilizing chimeric antigen receptor (CAR)-T cells have achieved remarkable effectiveness in individuals with hematological ...

Bioengineering

Engineering and Expansion of Human CAR Tregs for Immune Regulation Therapies

Generation of Human Chimeric Antigen Receptor Regulatory T Cells

Chimeric antigen receptor (CAR) T-cell therapy has reshaped the face of cancer treatment, leading to record remission rates in previously incurable hematological cancers. These successes have spurred interest in adapting the CAR platform to a small yet pivotal subset of CD4+ T cells primarily responsible for regulating and inhibiting the immune response, regulatory T cells (Tregs). The ability to redirect Tregs&#39; immunosuppressive activity to any extracellular target has enormous implications for creating cell therapies for autoimmune disease, organ transplant rejection, and graft-versus-host disease. Here, we describe in detail methodologies for bona fide Treg isolation from human peripheral blood, genetic modification of human Tregs utilizing either lentivirus or CRISPR/Cas9-aided knock-in using adeno-associated virus-mediated homologous directed repair (HDR) template delivery, and ex vivo expansion of stable human CAR Tregs. Lastly, we describe the assessment of human CAR Treg phenotypic stability and in vitro suppressive function, which provides insights into how the human CAR Tregs will behave in preclinical and clinical applications.

This protocol provides a streamlined workflow to generate and test human chimeric antigen receptor regulatory T cells (CAR Tregs).

Chimeric antigen receptor (CAR) T-cell therapy has reshaped the face of cancer treatment, leading to record remission rates in previously incurable ...

Droplet-based Cytotoxicity Assay to Assess Chimeric Antigen Receptor T cells at the Single-cell Level

The assessment of the cytotoxic potential of T cell-based therapies, such as chimeric antigen receptor (CAR) T cell treatments, is instrumental in assessing their efficacy and is a prerequisite for clinical application. However, traditional cytotoxicity assays are conducted as bulk assays and do not provide detailed information about the functional heterogeneity of the CAR T cell population. In this study, we describe a double-emulsion droplet-based method that allows for large-scale co-encapsulation of single effector CAR T cells with single target cells while enabling dual quantification of both cytotoxic effector molecules from T cells and cell death of the target cell. The protocol outlines a method for the generation and purification of CD19-specific CAR T cells, followed by their co-encapsulation in droplets with the CD19+ cell line JeKo-1, along with reagents to visualize cytotoxic effector molecule secretion (Granzyme B) and cell death (using propidium iodide, PI). We demonstrate how to generate droplets containing single CAR T and target cells using a commercially available microfluidics device for generating double emulsion droplets. Additionally, we provide examples of how to assay the functional diversity of CAR T cells in droplets using standard flow cytometry equipment. Finally, we briefly describe the temporal kinetics and heterogeneity of CD19-specific CAR T-cell killing. While this method focuses on cell death following a CAR T cell attack, it is also adaptable for examining other types of T cells, cytotoxic immune cells, and effector cell functions, such as cytokine secretion.

Here, we describe a method for creating double-emulsion droplets encapsulating one T cell and a cancer target cell to examine cell killing at the single-cell level. This method allows for dual quantification of both cytotoxic molecules and target-cell apoptosis within a large population of T cells.

The assessment of the cytotoxic potential of T cell-based therapies, such as chimeric antigen receptor (CAR) T cell treatments, is instrumental in ...

An Ex Vivo Technique to Manufacture Chimeric Antigen Receptor T Cells

Source: Ghassemi, S., et al. <a href="https://app.jove.com/v/59949">Manufacturing Chimeric Antigen Receptor (CAR) T Cells for Adoptive Immunotherapy.</a> J. Vis. Exp. (2019)
This video demonstrates a technique to manufacture chimeric antigen receptor (CAR) T cells ex vivo. Human T cells are incubated with magnetic beads coated with anti-CD3 and anti-CD28 antibodies, along with a medium supplemented with interleukin-2 (IL-2), leading to T cell activation and proliferation. Transgenic lentiviral vectors are introduced, allowing the transgenic RNA to integrate into the host genome and express the transgene. This results in the transduced T cells expressing chimeric antigen receptors (CARs) on their surface. The T cells are harvested at defined time points to assess CAR expression and cryopreservation.

All procedures involving sample collection have been performed in accordance with the institute&#39;s IRB guidelines.
1. T Cell Activation, Transduction, ...

JoVE Encyclopedia of Experiments

Immunology

Immunotherapy

Cellular Immunotherapy

An Ex Vivo Technique to Generate Tumor-Specific Chimeric Antigen Receptor T Cells

Source: Riccione, K., et al. <a href="https://app.jove.com/v/52397">Generation of CAR T Cells for Adoptive Therapy in the Context of Glioblastoma Standard of Care.</a> J. Vis. Exp. (2015).
This video demonstrates a technique for the ex vivo generation of tumor antigen-specific chimeric antigen receptor (CAR) T cells. Retroviral vectors carrying transgenic RNA are mixed with spleen cells in a medium supplemented with interleukin-2 to promote T-cell survival and proliferation. The mixture is then transferred to a plate coated with recombinant human fibronectin fragments and centrifuged to facilitate the fusion of the virus with the cell, allowing the RNA to integrate into the host genome and produce surface-bound CARs targeting the tumor antigen.

All procedures involving animal models have been reviewed by the local institutional animal care committee and the JoVE veterinary review board.
1. ...

Performing an In Vitro Genome-Wide CRISPR Knockout Screen in Chimeric Antigen Receptor T Cells

Samenvatting

Meer video's verkennen