Man's Best Friend: Utilizing Naturally Occurring Tumors in Dogs to Improve Chimeric Antigen Receptor T-cell Therapy for Human Cancers
Authors: Melinda Mata, Stephen Gottschalk
Journal: Molecular Therapy (2016)

See page 1602 Adoptive cellular immunotherapies for cancer, including the use of immune cells expressing chimeric antigen receptors (CARs), is a rapidly growing field. CARs are engineered proteins that combine the antigen specificity of a monoclonal antibody with the effector function of an immune cell.1Dotti G Gottschalk S Savoldo B Brenner MK ). Design and development of therapies using chimeric antigen receptor-expressing T cells.Immunol Rev. 2014; 257: 107-126Crossref PubMed Scopus (352) Google Scholar,2Sadelain M Brentjens R Riviere I The basic principles of chimeric antigen receptor design.Cancer Discov. 2013; 3: 388-398Crossref PubMed Scopus (857) Google Scholar When expressed on the surface of T cells, CARs redirect T-cell specificity toward malignant cells and elicit a direct antitumor response. CD19-CAR T cells have potent antitumor activity against CD19+ malignancies in humans;3Lee DW Kochenderfer JN Stetler-Stevenson M Cui YK Delbrook C Feldman SA et al.T cells expressing CD19 chimeric antigen receptors for acute lymphoblastic leukaemia in children and young adults: a phase 1 dose-escalation trial.Lancet. 2015; 385: 517-528Abstract Full Text Full Text PDF PubMed Scopus (2055) Google Scholar,4Maude SL Frey N Shaw PA Aplenc R Barrett DM Bunin NJ et al.Chimeric antigen receptor T cells for sustained remissions in leukemia.N Engl J Med. 2014; 371: 1507-1517Crossref PubMed Scopus (3554) Google Scholar,5Davila ML Riviere I Wang X Bartido S Park J Curran K et al.Efficacy and toxicity management of 19–28z CAR T cell therapy in B cell acute lymphoblastic leukemia.Sci Transl Med. 2014; 6: 224ra225Crossref Scopus (1760) Google Scholar however, common side effects such as cytokine release syndrome and/or neurotoxicity have not been observed in preclinical models.6Maude SL Barrett D Teachey DT Grupp SA Managing cytokine release syndrome associated with novel T cell-engaging therapies.Cancer J. 2014; 20: 119-122Crossref PubMed Scopus (517) Google Scholar In addition, CAR T cells have so far failed to produce notable clinical benefits for solid tumors despite promising results in preclinical models.7Maus MV June CH Making better chimeric antigen receptors for adoptive T-cell therapy.Clin Cancer Res. 2016; 22: 1875-1884Crossref PubMed Scopus (187) Google Scholar These failures are in part due to currently used animal models, which heavily rely on transplantable xenograft models. To overcome these limitations, Panjwani et al. in this issue of Molecular Therapy now describe the development of a CAR T-cell therapy for canines with spontaneously occurring lymphoma.8Panjwani MK Smith JB Schutsky K Gnanandarajah J O'Connor CM Powell Jr, DJ et al.Feasibility and safety of RNA-transfected CD20-specific chimeric antigen receptor T cells in dogs with spontaneous B cell lymphoma.Mol Ther. 2016; 24: 1602-1614Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar The domestic dog (Canis lupus familiaris) is an excellent model for human disease. More than 450 diseases have been described of which approximately 360 are analogous to a human disease, including several cancers such as lymphoma, osteosarcoma, leukemia, and melanoma.9Paoloni M Khanna C Translation of new cancer treatments from pet dogs to humans.Nat Rev Cancer. 2008; 8: 147-156Crossref PubMed Scopus (474) Google Scholar,10Shearin AL Ostrander EA Leading the way: canine models of genomics and disease.Dis Model Mech. 2010; 3: 27-34Crossref PubMed Scopus (121) Google Scholar Importantly, unlike the majority of inbred murine models in which tumors are transplanted, tumors occur spontaneously in canines, thereby recapitulating the natural tumor development and multifaceted tumor environment. Canine tumors also occur in different breeds, allowing the assessment of therapeutics in animals with an intact immune system and different genetic backgrounds. Thus, naturally occurring cancers in dogs offer a valuable opportunity to evaluate CAR T-cell therapy. The use of canine models to evaluate cell and gene therapies has a long-standing history. For example, studies three decades ago in canines with lymphoma demonstrated that autologous peripheral blood stem cell transplantation is a viable alternative to bone marrow transplantation.11Appelbaum FR Deeg HJ Storb R Graham TC Charrier K Bensinger W Cure of malignant lymphoma in dogs with peripheral blood stem cell transplantation.Transplantation. 1986; 42: 19-22Crossref PubMed Scopus (36) Google Scholar Correction of hemophilia B in canines by liver gene therapy was one of the first examples of successful gene therapy in a large-animal model,12Kay MA Rothenberg S Landen CN Bellinger DA Leland F Toman C et al.In vivo gene therapy of hemophilia B: sustained partial correction in factor IX–deficient dogs.Science. 1993; 262: 117-119Crossref PubMed Scopus (287) Google Scholar and adoptive transfer of genetically modified hematopoietic stem cells in canines demonstrated that it is safe and feasible to regulate gene expression in hematopoietic stem cells long term.13Okazuka K Beard BC Emery DW Schwarzwaelder K Spector MR Sale GE et al.Long-term regulation of genetically modified primary hematopoietic cells in dogs.Mol Ther. 2011; 19: 1287-1294Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar Adoptive cell therapy is also beginning to be explored. One study demonstrated that the infusion of ex vivo expanded autologous lymphocytes in canines with lymphoma is safe and associated with a survival benefit.14O'Connor CM Sheppard S Hartline CA Huls H Johnson M Palla SL et al.Adoptive T-cell therapy improves treatment of canine non-Hodgkin lymphoma post chemotherapy.Sci Rep. 2012; 2: 249Crossref PubMed Scopus (49) Google Scholar Canine lymphocytes have also been genetically modified with the herpes simplex virus thymidine kinase suicide gene15Weissinger EM Franz M Voss C Bonini C Kremmer E Kolb HJ Expression of HSV-TK suicide gene in primary T lymphocytes: the dog as a preclinical model.Cytokines Cell Mol Ther. 2000; 6: 25-33Crossref PubMed Scopus (12) Google Scholar or HER2-specific CARs,16Mata M Vera JF Gerken C Rooney CM Miller T Pfent C et al.Toward immunotherapy with redirected T cells in a large animal model: ex vivo activation, expansion, and genetic modification of canine T cells.J Immunother. 2014; 37: 407-415Crossref PubMed Scopus (50) Google Scholar but canine CAR T-cell therapy has so far not been tested in vivo. In their study, Panjwani et al.8Panjwani MK Smith JB Schutsky K Gnanandarajah J O'Connor CM Powell Jr, DJ et al.Feasibility and safety of RNA-transfected CD20-specific chimeric antigen receptor T cells in dogs with spontaneous B cell lymphoma.Mol Ther. 2016; 24: 1602-1614Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar modified previous methods to activate and expand canine T cells ex vivo by using artificial antigen-presenting cells genetically modified to express human CD32 and canine CD86. These artificial antigen-presenting cells were loaded with a canine CD3 monoclonal antibody and used in combination with human interleukins (IL)2 and IL21 to preferentially expand CD8+ T cells.14O'Connor CM Sheppard S Hartline CA Huls H Johnson M Palla SL et al.Adoptive T-cell therapy improves treatment of canine non-Hodgkin lymphoma post chemotherapy.Sci Rep. 2012; 2: 249Crossref PubMed Scopus (49) Google Scholar,16Mata M Vera JF Gerken C Rooney CM Miller T Pfent C et al.Toward immunotherapy with redirected T cells in a large animal model: ex vivo activation, expansion, and genetic modification of canine T cells.J Immunother. 2014; 37: 407-415Crossref PubMed Scopus (50) Google Scholar CD20-CAR–expressing canine T cells (CD20-CAR T cells) were generated by messenger RNA electroporation, and CD20-CAR T cells recognized and killed lymphoma cells in a CD20-dependent manner. To test in vivo the efficacy of canine CD20-CAR T cells, a client-owned dog with relapsed spontaneous B-cell lymphoma was infused three times with autologous CD20-CAR T cells. T-cell infusions were safe, but antitumor activity was limited. Limited antitumor activity is most likely due to several factors including limited CAR T-cell expansion, transient CAR expression, and the development of canine antimouse antibodies. Thus, lymphodepletion before T-cell infusion17Dudley ME Yang JC Sherry R Hughes MS Royal R Kammula U et al.Adoptive cell therapy for patients with metastatic melanoma: evaluation of intensive myeloablative chemoradiation preparative regimens.J Clin Oncol. 2008; 26: 5233-5239Crossref PubMed Scopus (1084) Google Scholar and the use of vectors that allow for persistent CAR expression hold promise to improve outcomes. Lymphodepleting chemotherapy should also reduce the risk of inducing canine antimouse antibodies. Despite the attractive features of canine models, one potential drawback for studying CAR T-cell therapies is the lack of immunological reagents to carefully analyze for example T-cell subsets. Thus, the study by Panjwani et al.8Panjwani MK Smith JB Schutsky K Gnanandarajah J O'Connor CM Powell Jr, DJ et al.Feasibility and safety of RNA-transfected CD20-specific chimeric antigen receptor T cells in dogs with spontaneous B cell lymphoma.Mol Ther. 2016; 24: 1602-1614Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar should serve as an incentive to generate these. This will be especially important for future combinatorial therapies in which CAR T cells are combined with other targeted immunotherapeutics such as checkpoint blockade.18Maekawa N Konnai S Ikebuchi R Okagawa T Adachi M Takagi S et al.Expression of PD-L1 on canine tumor cells and enhancement of IFN-gamma production from tumor-infiltrating cells by PD-L1 blockade.PloS One. 2014; 9: e98415Crossref PubMed Scopus (70) Google Scholar Finally, the recently released National Institutes of Health guidelines for research involving "recombinant or synthetic nucleic acid molecules"19National Institutes of Health Office of Science Policy, 2016. NIH Guidelines for Research Involving Recombinant or Synthetic Nucleic Acid Molecules (NIH Guidelines) <http://osp.od.nih.gov/sites/default/files/NIH_Guidelines.html>Google Scholar do not explicitly discuss therapies with genetically modified cells that have a finite lifespan in client-owned animals. Only if infused animals can be returned to their owner, and the regulatory requirements are less burdensome than for performing clinical studies in humans, will CAR T-cell therapy in client-owned animals flourish. In conclusion, the article by Panjwani et al.8Panjwani MK Smith JB Schutsky K Gnanandarajah J O'Connor CM Powell Jr, DJ et al.Feasibility and safety of RNA-transfected CD20-specific chimeric antigen receptor T cells in dogs with spontaneous B cell lymphoma.Mol Ther. 2016; 24: 1602-1614Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar opens the door to evaluate CAR T cells in canines. Testing CAR T-cell therapies in canines has the potential to serve as an intermediate between murine models and human clinical trials, enabling rapid testing of promising candidates to select the best CAR T-cell product for clinical studies (Figure 1). This approach holds promise to improve outcomes not only for cancer patients but also for "man's best friend" diagnosed with cancer. The authors received support for their solid-tumor research from National Institutes of Health grants 1R01CA148748–01A1, 1R01CA173750–01, and P01CA094237; CPRIT grant RP101335; the V Foundation; the Rally Foundation for Childhood Cancer Research; the Sarcoma Foundation of America; the L3 Foundation; and Cookies for Kid's Cancer.